FIELD TEST AGENDA P-101B, COMMUNICATION SYSTEM, INFRARED

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP78-03300A001600020097-5
• Release Decision: RIPPUB
• Original Classification: S
• Document Page Count: 98
• Document Creation Date: December 22, 2016
• Document Release Date: December 28, 2011
• Sequence Number: 97
• Publication Date: December 2, 1954
• Content Type: REPORT

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DOCUMENT NO. NFIDENT1AL
:NO 01-1;',NC.177!! Cli.SS. 0
0 DECLASSIFIED
CLASS. CHANCED TO: TS
NEXT REVIEW DATE:
'MTH: 70
DATE -EVIEWER? 010956
s 041,ttit,0
2 DeceMber 17)4
FIELD TEST AGENDA
P4013? Communication System, Infrared
I. Test Objectives
A. Range Tests
The primary Objective of the tests is to determine the
performance of the equipment as a function of the range and to
fix the approximate maximum ACW ranges for day and night
operations.
D. General Eojijent Performance Teats
The secondarydbjective of the test is to determine the
general equipment performance under typical operating conditions.
Particular note will be made of these points:
1. Mechanical Features
4. APparent quattyof mechanical construction overall
b. Waterproofing of equipment Closed and open
c. Apparent resistance to shock and vibration
d. Ruggedness and stability of tripod table
e. Yoke mount performance and limitations
(1) Maximum angular swing of equipment in owinin:th
and elevation
Presence of wobble, backlash, stickiness, etc.
in the yoke mounting
(2)
(3)
Accuracy of horizontal and vertical circles and
the ease with which they may be read
(4) Mechanical sweep mechanism performance
f. Mechanical construction of the optical systems.
(1) Quality of glass Objective mirror mounting
(2) Ruggedness and stability of mount for the optical
sight
(3) Ruggedness and reliability of the bellows system
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(4) StabiLity of the galvanometer system of Modulation
(5) Protection for and mounting of the glass IR filter
2. Optical Feature?
a. I. R. viewer
Sensitivity (night and day ranges)
Field of view
Quality of reticle MI ease of sighting
Optical quality of image
Alignment of viewer with main optical system
' ity
/(3) Al st sigh th main
Electrical Features
a. Amplifier noise level
b. Signal intelligibility
0. Possibilities of voice recognition
4. Battery performance
tional Feasibilit Tests
en reFe test is to determine the
feasibility of using the equipment under various operational
conditions. Particular attention will be paid to the following
items:
1. The ease of opening the Gear and assembling It, e.g., the
time required to put the equipment into operation
2. The value of the controls provided and the ease with which
they may be used
3. The suitability of the two foot high tripod for operations
in varying terrain
CONF1 ENT1AL
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SRC . CONFIDENTIAL
D.
4. The suitability of the angular swinge in azimuth and
elevation, relative to the tripod Uwe, made possible by
the present equipment design
5. The operational procedures used and the time reqpired to
accomplish the search-find operation using each procedure
Cctplete Plx:rtotir ? ? c Co....terk of the Equiment in tion
e fourth .? jaCtive Ue?tiir is o obtaiTa cturea of
the equipmerct'in operation. It is felt that photographs of the
terminal areas, both close ups and telescopic view's frau the
other terminal, would be of interest to readers of a teat
report, since such photographs +would give an excellent idea
of field conditions, etc.
Test Procedures
A. Selection of Field Test Locations
1. Using the 1:62,500 1.1308 maps of the area, select e or 3
locations for line of-sight ranges of 1,2,4,6,8 sdlea
approximately
2. Make elevation plots of each of these ranges to check for
line-of-sitt.t6 j
3. Select, obab3,41 nj.ght and day l: irks from the map to
facial te the location Of the terminal stations
Note the respective bearings of each station from the
other in azimuth iwilk-eimmiliMiee as obtained from the
map. Also note the bearings of the landmarks.
B. Field Test Procedures
1. Form two teams of two men each; one team for e station
of the rangy, in question . eqa aA%-t-c
-
---r1A-7!--V
uP-signal plans for the range* selected in IIA including:
a. Map overlay of both stotions
b. Map
6. /
,"
' 2
a #det
N -414,a4NOtileaaiggete
de 06--L,.-10 62,-,4-4fla awl-4
4. ,Bearing of each station from the other
) e. List of day and night landmarks and. their bearinge)et, a-4-2-1-
/
.0) per4IJ,a-4.4
f. Time to initiate search-find. procedure
d.Antlelt,
g? Time to discontinue search-find procedure failing contact
3 - CONFIDENTIAL
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,SEORETtONh LENTiAt_.
Select a mile range from those of ti.A
a. Send. one team to each station by daylig,at
b. On this first visit to each station by de/light
(1) Locate an operating area and set up gear. Record
time required
(2)
(3)
Locate position of other station by landmarks,
compass bearing
Using optical eight and mechanical sweep execute
aearch..find procedure until contact is established.
Record time required.
Note the horizontal and vertical circle readings
for various landmarks
(5) Take photos of
(a) The gear in operation and its surroundings
(b) The other station with 50 and 1400 mm lenses
(6) Review the General Equipment Performance Tests
an& make pertinent comments
(7) Recordlmeather condition*, visibility, temperature, etc.
)3) 41,4)
On the second visit to each station by night
(I)
(2)
(3)
Set up the gear in the previously located area.
Record the time required
Locate position of other station from bearings of
landmarks previously noted
Using infrared viewer and mechanical sweep execute
sweep-find procedure. Establish contact. Record
time required
(4) Review General Equipment Performance Tests and. make
pertinent comments
(5) Record weather conditions
aiyia ( -47--614)
Report the procedure ottlined!under 3, 3 for other ranges,
shorter or longer as required under different terrain conditions
5. Repeat B,3,c for a pzieviously =surveyed site
CONFIDr:NTIAL
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XIX. Test Results
.6 EGRET
Ai:JAJ -11
A. Alist of the ranges obt&tnd with the signal quality and
weather conditions noted
R. Descriptions of the operational situations involved, the
search-find methods used for each situation, and the time
required to establigh contact in each case
C. A description of the overall equipment performance with
suggested improvements
25X1
Distribution:
Orig. - P401B.
3 - AOT V
2. - Chr ono
.ASTtbb
TBS/APD
5 CONF
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Friend or foe? In pitch blackness the snooper.
cope will tell whether stray noises ore cpused
by a late-returning husband or a midnight prowler.
make this
SNOOPERSCOPE
and see in
total darkness
By Harold Polies
PICTURED above is only one of the pos-
sible applications of the modified war-
time sniperscope. This unit, called a
snooperscope, is an enlarged version of the
instrument used by GI riflemen to enable
accurate fire power in total darkness. When
the infrared light source is turned on, the
user, by employing the special eyepiece,
can see in the area covered by the light,
although to the naked eye total darkness
still prevails.
A number of more practical applications
have been developed with the snooperscope
because of its ability to peer through any
opaque material that passes infrared rays.
Crime detection laboratories are now using
similar equipment for reading through cer-
tain types of material. Since the infrared
reflection of pigments in paints and inks is
different from that of white light, it is pos-
sible to detect forged paintings and checks
by the way the colors appear. You can
demonstrate this by writing a message with
India ink and then painting over it with a
coat of ordinary fountain pen ink. Your eye
will only see the blackened spot but the
snooperscope will peer through the top
Reprinted from llerhanil Illustrated llagazinc
Copyight 19-31, Faucet; Publications, Is.
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Declassified
GRAPHITE COATING METAL RING
1' FOCAL LENGTH
MAGNIFIER LENS
(TRIPOD TYPE)
PAINT WALLS
FLAT BLACK
NEAR
INFRA RED
ALTER
IMAGE
CONVERTER
TUBE
31/2* FOCAL
LENGTH
EYEPIECE
(OPTIONAL)
3 1/24
HOLE CUT IN CUP BOTTOM
FOR MAGNIFIER LENS
(SLOTS CLEAR TRIPOD STUBS)
PLASTIC
HANDLE BAR
GRIP
1/8' PLASTIC
? DISK CUPS
ARRANGEMENT OF UNITS INTO PLASTIC DRINKING CUP ONTO RIM
layer of ink and reveal the writing just as ness. A converter tube has been used with
clearly as if there were no top coating. This a microscope to study bacteriological and
type of inspection can be made photo- botanical specimens under infrared rays.
graphically if infrared film is used in the Certain large molecules may now be ex-
camera. The electronic method hermits amined in a different way, since they be-
instantaneous examination which often is come transparent under infrared light.
a 'great convenience. Military uses are obvious. The sniper-
As you might have thought, there are scope has already been mentioned. The
several photographic applications. Using Germans used infrared-equipped tanks
this device, you can take photographs with and trucks for driving during blackouts.
no visible light source. (For instructions Under these conditions they could travel
on this type of work, see Shoot 'Em In The almost as fast as during the day. Cars
Dark, January, 1951, MI, pgs. 148-149.) equipped with a snooperscope would have
One of the handiest uses is using the snoop- the advantage during fog. Certain types of
erscope as a darkroom viewer. Difficult op- fog are transparent to infrared (depend-
erations that have to be carried out in total ing on the particle sizes) and during such
darkness can now be viewed clearly weather increased safety of the road could
throughout the process. If you run into be obtained. The experimenter is cautioned
trouble loading film tanks you will appre- about building a unit for this purpose, as
ciate a viewer when the film becomes very good lenses are required as well as
snarled. A test for fogging should be made powerful headlights. Such specialized con-
before the viewer is used. Within the next struction is likely to prove difficult and
few years every modern darkroom may be driving with makeshift equipment would
equipped with infrared viewers, be dangerous.
In scientific laboratories a modified unit In the actual construction of your snoop-
such as this is used to study the behaviour erscope, your 13, ,e would be one of
of small nocturnal animals in total dark- several British in. , which are available
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Glass type Infrared filter
To 115 v
AC-DC
300-watt
115 volt
outdoor
type
floodlight
Plywood
case
UNIT FOR SUPPLYING LIGHT SOURCE
on the surplus market. Two of these are
type CRI 143 and CV 147. For op,eration at
the highest voltages, the tubes should be
carefully selected. Other electronic parts
required are a 4,000 to 6,000-volt low cur-
rent power supply (less than one milliam-
pere), a light source and two filters.
For indoor operation a 4,000 to 5,000 volt
neon sign transformer operates the tube
satisfactorily. Two 1-megohm resistors are
used, one in series with each lead, to limit
the current. Rectification is not necessary
unless the objects are in motion (objects
in motion cause a stroboscopic effect when
AC is employed.
For portable use either indoors or out-
doors a handy-sized power supply may be
constructedthat operates off three standard
flashlight cells. For continuous operation
leave the power supply on as long as re-
quired. Very long battery life can be ob-
tained by switching on the power supply
only momentarily to charge the condenser.
The condenser will then store this energy
and continue to operate the tube for some ?
time after the unit is turned off. Place a
small piece of rubber tubing over toggle
switch handle to help eliminate charge
pickup.
The high voltage is supplied by a model
airplane ignition transformer with a vi-
brator to interrupt the primary current.
These transformers are available on the
market with the vibrator already built in.
Only two wires need be attached for op-
eration. You can make up your own vi-
brator coil arrangement by using the parts .
of an old buzzer or bell. Some types of buz-
zers can simply be connected in series with
the primary of the transformer. Try yours
- . _
Elements of the light source. Bulb employed Is a
standard 100 to 300-watt lamp. Although this case
is of metal, you may use plywood if so desired.
to see if this is possible (11/2 volt buzzers).
Caution: Avoid contact; these voltages
are high and while not dangerous, can
give you a rather uncomfortable shock.
Construction of the snooperscope: The
image converter tube is mounted in a plas-
tic drinking cup 31/2 in. high by 21/2 in. in
diameter. The optical system required de-
pends upon your intended use. We used a
small tripod type magnifier lens of 10 power
(1 in. focal length) for the front lens and
objects from three inches to one and a half
feet can be focused. There is no reason why
a greater range cannot be had with this lens
by moving it closer or farther away from
the tube.
After selecting the lens system mount it
in a hole cut into the bottom of the cup. A
jeweler's saw or coping saw is ideal for cut-
ting the hole. Paint the inside of the cup
with black paint. Black airplane dope
works fine. No light other than that from
the lens must be permitted to hit the tube.
Place an infrared filter between tube and
lens to reduce effects of stray white light.
The image converter tube is inserted
with the graphite side toward the front
lens and the metal ring toward the mouth
of the cup. A thin flexible lead from the
metal ring connects to the positive side of
the power supply. Some tubes were manu-
factured without this lead, in which case a
piece of spring metal pressed against the
metal ring will work just as well. The front
end of the tube has a graphite ring around
it. This is the end where the infrared image
is to be focused. The graphite coating is the
cathode or negative lead. Connect this lead
to the B minus side of the power supply. A
piece of spring
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Top view of simplified power supply for portable The snooperscope itself. For indoor use a small
use. Cells are the ordinary flashlight type. The en- neon sign transformer (right) may be used to
tire unit is mounted on a 3/4-in, plywood baseboard, power the infrared tube within the plastic cup.
Model airplane
Ignition transformer
with vibrator
To graphite
coated ring
on tube
High tension lead
1/2 megohm resistor
'...44414114141/411110:bifj
?
, Condenser
.1 mfd
600 v
For 1X2A tube, use 'pins 2 & 6
For 1B3GT/8016 tube, use 2 & 7
Three -"D"
1.5 volt
flashlight
tells
PORTABLE POWER SUPPLY UNITS ON WOOD PANEL
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brass or even the flat sheet metal carefully
removed from a tin can should be formed
with the fingers so it fits snugly around the
cathode terminal.
The rear viewing lens is optional as it is
only required if yOu wish to view the images
closely with the eye. It should have about
three power and a focal length between 21/2
and 4 in. This lens is mounted and cemented
to a piece of plastic or wood. The material
should be opaque and have good insulating
qualities. The handle is a plastic bicycle han-
dlebar grip which is cemented over a hole
drilled into the side of the 'drinking cup for
the high voltage leads. The lead wire can be
the plastic type of zip cora, over which is
placed plastic insulating tubing.
Light source: The main limit to the view-
ing distance is the power and type of light
source. Greater intensity means greater dis-
tance. For the direct viewing of glowing
objects this imposes little difficulty. Such ob-
jects as the moon and extra bright stars may
be viewed directly. A small flashlight with a
plastic filter may be detected at quite a dis-
tance. Reflected light from objects requires
the use of heat lamps, photofloods or standard
100 to 300-watt lamps to illuminate them. Of
course these lights are filtered so that no
visible light is seen. The light source shown
on page 100 consists of a 300 watt sealed beam
outdoor type floodlight (115 volt), a glass
type infrared filter and a 10x10 in. recessed
lighting box.
Outdoor applications involving greater
distances require a bulb with a sharply fo-
cused reflector. Gold-plated reflectors give
very good results. The sniperscope used a 30
watt, 6 volt bulb similar to the type used in
auto headlights. This was operated on a small
rechargeable storage battery. Good substi-
tutes are auto spotlights of the sealed beam
type such as Westinghouse type 4535 or the
General Electric 4524. Standard type flash-
lights with small dry cells will not provide
ample infrared for viewing by reflection.
Never point your snooperscope at extremely
bright light sources like the sun. Damage to
the tube may result.
Infrared filters: Experimental filters can be
made by sandwiching several layers of dark
red and blue cellophane between two sheets
of clear plastic. Both plastic and glass types
are available from photographic and scientific
supply houses. The latter type is to be used
whenever heat is involved. Infrared filters
cut out all or most of the visible radiation and
allow the heat rays to pass through unob-
structed. Since a tungsten lamp produces
much more infrared than it does visible light,
the action of a filter reduces its strength only
slightly, while to our eyes it now becomes
total black. Don't forget that it is possible
to overheat even glass filters, so light sources
shotild not be left on longer than necessary. ?
SNOOPERSCOPE PARTS LIST
Light Source: ,
Sealed beam light or standard 100 'to 300-
watt lamp and reflector
Metal housing for above items
Infrared filter
Snooperscope (Eyepiece unit):
Image converter tube
Plastic drinking cup
Plastic handlebar grip ?
Jeweler's eye loupe (approximately 2 to 4-in.
focal length)
Tripod magnifier, approximately 10x, I-in, focal
length
Five ft. plastic-insulated cord (do not use
cord with rubber or cloth insulation)
Near infrared filter
Black paint or airplane dope
Power Supply, AC:
Neon sign transformer, 4 to 5 kilovolts at under
10 mills current rating
Two 1/2-megohm resistors (may be as high as
5 meg.)
Power Supply, Portable:
Three flashlight cells
Model airplane ignition coil
Small buzzer
.005 mfd. condenser, 6,000 volts
.1 mfd. condenser, 600 volts (if not built into
vibrator coil)
Two 1/2-megohm resistors
lx2A or IB3GT/8016 tube
Socket for above tube
Wooden baseboard
D.P.S.T. switch
Grid cap
Two fahnestock clips
Note: These parts may be obtained from the
P. ecise Measurements Co., 942 Kings Highway,
Brooklyn 23, N. Y.
A
Beautiful AEROLUX CHEER. LITES
Flowers and Emblems inside of bulbs glow in natural
colors.
Solid brass Maple Leaf lamp holder and bulb? mos
Flowers or Merry Xmas bulbs (A & 13)? 1.75
Crucifix bulb? 1.00
FLUORESCENT PIGMENTS
Brightest glowing. concentrated phosphors,
available in many colors. Red, White, Blue,
Green, Yellow and Orange. Mix with clear
lacquer for painting.
SAMPLE SIZE (specify color) 35c each
COMPLETE SAMPLE KIT (6 colors). 81.75 ea.
One Ounce Bottles (apecify color) 50c each
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PRECISE MEASUREMENTS COMPANY -
SNOOPERSCOPE SUPPLIES
?We have a limited quantity of the following
supplies for the construction of snooperscope out-
fits. All material is in new condition and carries our
11 warranty to be free of defects in material or work-
manship.
SNOOPERSCOPE TUBE
SEE IN THE DARK
SUPPLY LIMITED?
These are government
released British
snooperscope tubes
which employ the spe-
cial simplified design,
makin? construction of
experimental models
possible with simple
hand tools. Highly sen-
sitive, they provide a
bright clear image of
invisible infra red rays,
Also useful as infra red (invisible) photocells.
With complete hookup instructions. Special
Price $14.95.
ENGRAVERS GLASS?Has a ground lens
for clear sharp images. Focal length three
inches. Perfect as either a front or rear
view lens. Plastic housing prevents elec-
tric shock. Price 1.25
SNOOPERSCOPE BOOK
Shows in detail Army and Navy
snooperscopes, sniperscopes and infra
red telescopes. One of the few books of
its kind. Circuit hookups for practical
instruments are given.
Special Price $1.50.
NEAR INFRA RED FILTER?An efficient
filter that fits directly on the front of the
image converter tube. High quality glass
type with metal mounting clasp. Clasp
also serves as the graphite contactor
(?lead). Your Price LW
IGNITION COIL?This miniature high volt.
age coil provides high output for snooper-
scope operation. Has built in condenser
for extra power. Special $2.25
PLASTIC FILTERS
Infra red plastic filers are also available at 15? each for small test square
and 750 each for 6 x 6 inch squares. Permits passage of heat rays but
appears black to visible light. Buy several at this price while the supply
lasts.
FILTERS?Infra red filter glass. Manufac-
tured by a famous glass house to exacting
specifications. Transmitts over 80% of
the infra red rays but appears as a total
black for visible light.
3 x 3 inch square Price $2.55
6 x 6 inch square Price $4.00
PA" Round $3.75
942 Kings Highway, Brooklyn 23, New York
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ADDITIONAL
INFRA RED SNOOPERSCOPE SUPPLIES
The following additional supplies were made available due to many
requests for materials with which to construct experimental infra red
instruments and snooperscopes. Sales of any item is limited to stock
now on hand. New materials arriving dolly.
POWER SUPPLY KIT?Provides the proper voltages for image converter
tubes. Operates off three ordinary flashlight cells. Completely portable.
Every part including case, rectifier tube and batteries is supplied.
Your price $14.93
LENSES?These lenses are of top quality materials and intended for use
where the best possible results are required. We make these lenses
available only to our customers which have purchased our snooperscope
tubes and send us there written assurance that they have been success-
ful with the circuits and the simple lenses and now feel prepared to
construct the finer models.
SNOOPERSCOPE LENS ? Original Navy
Snooperscope lens. Schmidt optical system
type Government cost $134.00. Very fast
speed F 1.0 Our Price $12.50
Mounted Optical Lens. High quality
lens of fast speed. Excellent for
image tubes. Priced at a fraction of
their original cost. Price $8.50
HOW TO ORDER
IMPORTANT NOTICE
Sales are subject to the following conditions; all prices in this catalogup
is subject to change without notice. Most material is shipped postpaid unless
otherwise noted. Test instruments are not postpaid and postage fees should
be included with your order. We will insure all material unless instructed other-
wise. In the event of damage in transit, write us immediately giving details o
f the damage and insurance numbers on package. If for any reason you wish
to return material write us first giving all detai's and we will send you ship
ping instructions. POSITIVELY NO MATERIAL ACCEPTED FOR RETURN UNTIL
WE HAVE BEEN NOTIFIED AND YOU HAVE OUR SHIPPING INSTRUCTIONS.
Merchandise made to customers own specifications cannot be returned. Foreign
orders should add 10% to cover costs of additional packing, postage and con
sular expenses. No C.O.D. orders accepted unless accompanied by a deposit 0
25%, balance wil be shipped C.O.D.
This catalogue covers only a few of the items that we carry. We carry
hundreds of items not listed on these pages write us on your requirements.
Prompt efficient service is rendered on all orders regard'ess of size. Our lab
oratory is engaged in the construction of scientific instruments of every de-
scription. We are always very happy to send our free quotations on equipm
On? built to order.
PRECISE MEASUREMENTS COMPANY
942 Kings Highway, Brooklyn 23, New York
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I. It I 1?lil I I I 1 I I 11
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GE OZONE. LAMP
ent1,11,114.5,
7;1
BLACKLIGHT LAMP
Special Argon filled bulb pro-
vides a good source of violet and
ultraviolet light for blackout
experiments and fluorescent
materials. Very convenient as It
screws into any standard lamp
socket.
Clearance Price 45e
10 for $4.00
Generates short ultraviolet
radiation (1849A & 2537A) which
produces ozone by converting
the oxygen of the air (02) into
ozone (CP). Useful for fluores-
cent & phosphorescent ma-
terials. Uses only '4 watts of
power. Lamp supplied with
socket and instructions.
Your Price $1.95
FLUORESCENT PIGMENTS
Brightest glowing, concentrated phosphors,
available in many colors. Red, White, Blue,
Green, Yellow and Orange. Mix with clear
lacquer for painting.
SAMPLE SIZE (specify color) 35e each
COMPLETE SAMPLE KIT (6 colors) $1.75 ea.
One Ounce Bottles (specify color) 50c each
AMAZING BLACK LIGHTS
Powerful 250 watt Ultra Violet
Bulb is very convenient to use
as it screws into any standard
lamp socket. Provides black light
which causes many things to glow.
Excellent for experimenting with
fluorescent and phosphorescent
pigments. Lamp is designed for
intermittent duty only.
Price $1.95
PHOSPHORESCENT PIGMENTS. Expose these pigments to sunlight or ultra
violet light or ordinary light bulbs. Pigments wil then remain glowing for
sometime afterward in total darkness. Comes in powder form mix with
clear lacquer for painting. Available in three colors: yellow-orange,
green and blue. t One ounce bottle 60? 1/2 pound bottle $2.75
SAMPLE KIT. Consists of one of each of the above cooks (three bottles).
Price 98 cents.
SPECIAL PHOSPHORS
ULTRA VIOLET
Energize this phosphor with short wave ultra
violet light (approx. 2500 A) and it will convert
it to the near ultra violet of approx. 4000 A.
This phosphor when used with many types of
black lights will increase the ultra violet out-
put considerably. Use as a coating on the out-
side of photocells to change their response.
Sample 50( 1 oz. Bottle $1 $12.50 lb.
SHORT WAVE
Responds to wavelength of 2500 A or shorter.
Will detect alpha particles, electron beams, etc.
Lights up a bright green.
Sample 50? $12.50 lb. 1 oz. Bottle $1
TWO COLOR
The beautiful colors that these concentrated
phosphors will glow depend upon the wave-
length. Different types of blacklights will make
it change color. Red and green or yellow and
green are available.
Sample 500 $12.50 lb. 1 oz. Bottle $1
INFRA RED EMITTING
This unusual material has the property of emit-
ting far red and infra red radiation when ex-
cited with ultra violet light. Useful as infra red
light sources, experimental fluorescent lights,
etc. Price $4 oz.
INFRA RED RESPONSIVE
A specially prepared material with rare earth
activators. Charge with ultra violet light or
alpha particles, phosphor then stores this en-
ergy and releases it in the form of light when
infra red radiation is present. Also useful as
temperature indicators.
Price $4 oz.
ULTRA VIOLET FILTERS
Glass type. Filters out most of the visible light
while allowing free passage of ultra violet.
Very handy for experimenting with fluorescent
phosphors. s
3 x 3 inch square Price $2.55
6 x 6 inch square Price $4.00
PRECISE MEASUREMENTS COMPANY
942 Kings Highway, Brooklyn 23, New York
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_I .. it I _
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TRIPOD MAGNIFIER ULTRA VIOLET GENERATOR
Lenses are ground for better clearity. Has high
magnification power and is adjustable by means
of a screw thread. Very popular item with ex-
perimenters, colleges and research labs.
Your Price $1.75
MICRO CIRCLE
CUTTER
FOR METAL ?
WOOD ? PLASTICS
? Micrometer type size control
? Extra heavy duty beam
? Special beam locking
mechanism
At all Dealers
Model Type Size Price
1 Round shank 4 inch $5.00
1 Square shank 4 inch 5.00
5 Round shank 6 inch 7.50
PRECISE COMPANY, 942 Kings Highway
BROOKLYN 23, NEW YORK
VAN DE GRAAF MACHINE
Produces voltages between 10 KV and 100 KV.
Well designed for long life and efficient opera-
tion. Under favorable weather conditions sparks
up to three inches can be obtained. Many in-
teresting high voltage experiments can be per-
formed with this miniature generator.
Price $15.00
12537 Angstrom units 1
Consists of a miniature mercury vapor lamp in
beautiful plastic housing. Lamp constructed of
special glasses for the efficient production of
ultra violet radiation. Built in ballasts for long
life and good operation. Wavelength changer
filter instantly changes the output wavelengths
Your Price $9.95
WAVELENGTH CHANGER FILTERS
available in blue, green, yellow, orange and
red. Price $1 each
INFRA RED WAVELENGTH
CHANGER FILTERS
Converts your ultra violet generator to an infra
red generator. Price $1.50 each
NIGHT VISION GOGGLES.?These gogglee
were used by the Army for nighttime
vision purposes. All are new and in indivi-
dual cloth case. Price $1.00 esch
INFRARED FILM. A fortunate purchase of infrared film allows us to offer
this material at an almost unbelievable low price. Film is surplus aerial,
cameral stock which is outdated. We have tested this film and find that
good results can still be obtained. Speed rating is 50 with red filter.
Comes in vacuum sealed can in rolls 51/2 inches wide by 26 feet long.
Your Price $1.25
CESIUM VAPOR LAMPS
These lamps produce nearly a pure output of infra red light of 8521
and 8943 Angstrom units. They are the most efficient source of infra red
at these wavelengths and are about 700% more efficient than the Tung-
stem filament lamp. These lamps may be modulated up to 10,000 cycles
with voice or code. Only a very limited quantity of these lamps are
available as they were used in Navy projects. Lamps are rated at 90
Watts at 5.5 amperes. Pries $30.00 sash.
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I ,.LIt_11 Hit! I I 111.1 ? 11111 11,? 1 1111. LL I1_L111 L I LIJ .1,141 L LLI J 1 II 1 11.11. bait
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No. 2425 READING DIFFRACTION SPECTROSCOPE.
This spectroscope is suitable for medical research, analytical work and general
purposes in physical laboratories.
The dispersion is 34? and the slit is provided with an adjustment for varying
the width. A graduated drum by which the spectrum can be moved, across the
field, used in conjunction with an indicator enables readings to be taken. This
drum is divided intolOOdivisions, which are arbitrary, but which can be calibrated
if desired by the user. An adjustment is fitted for accurately focussing the
spectrum.
A table stand to carry the spectroscope can be supplied. Provision is afforded
for the attachment of a test tube holder and also a cylindrical lens attachment.
This latter is a very useful accessory, especially when working with a small or
weak source of light, as it -concentrates an image of the light source on the slit.
No. 2425. Reading spectroscope, in case
? $69.50
Nos. 2458 and 2459 PRISM SPECTROSCOPES.
For certain purposes the prismatic type of spectrosco' pe is advantageous, as it
passes very much more light than the diffraction type. The dispersion, however,
is less, and as explained in the opening description (page 1), gives a smaller relative
dispersion at the red end of the spectrum compared with that at the blue end.
This model employs a train of five prisms giving a dispersion of 100. An
adjustment is provided to the slit for varying the width ; there is also an
adjustment for accurately focussing the spectrum. The instrument can he
attached to a table stand, and provision is made for the attachment of a test
tube holder, etc.
No. 2459 has the addition of a comparison prism. This enables the spectra from
two sources to be examined simultaneously.
No. 2458. Prism spectroscope, in case 49.50
No. 2459. Prism spectroscope, in case 52.95
PRECISE MEASUREMENTS COMPANY Brooklyn 23, New York
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il I III I' 1 I 11111:1 11.11M ihiiIIIIIHIHJLLI Jill L, I I
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Nos. 2522 and 2523 WAVELENGTH PRISM SPECTROSCOPES.
For taking direct readings in wavelengths, where extreme accuracy is not
required, this instrument will be found extremely satisfactory. The dispersion
given is 10'. The scale giving readings in wavelengths is viewed in the same
field as the spectrum, each division of the scale 'representing 100 A. The
slit is adjustable and the necessary focussing adjustments are provided. There
is also an adjustment to the scale so that it can be set accurately in relation
to the spectrum.
Provision for attaching to a table stand is provided and such accessories as test
tube holder and cylindrical lens attachment can be employed.
No. 2523 has the addition of a comparison prism. This enables the spectrum
being examined to be compared with a standard ? or other source.
No. 2522. Prism spectroscope, in case
$$9849..5500
No. 2523. Prism spectroscope, in case
ACCESSORIES
TABLE STAND.
This stand is strongly made, the spread of the feet is arranged to ensure that
the stand is rigid. The fitting carrying the spectroscope has adjustments for.
raising and lowering, also for tilting, both adjustments being provided with
clamps. It is suitable for spectroscopes Nos. 2447, 2449, 2425, 2426, 3500,
2458, 2459, 2522, 2523. 2435 and 2438.
No. 2437. Table stand . . ? . ? ? ? ? $995
CYLINDRICAL LENS ATTACHMENT.
When small or weak sources of light are being
examined, this attachment is found extremely
II useful, as it produces an extended image of the
light source on the slit. It can be used in con-
junction with Nos. 2447, 2449, 2425, 2426, 3500,
2458, 2459, 2522 and 2523.
No. 2496. Cylindrical lens
attachment ..
CYLINDRICAL LENS ATTACHMENT.
This attachment is on the same principle as No. 2496, but is made in quartz so
that it can be used in conjunction with spectroscopes Nos. 2435 and 2438.
No. 2436. Cylindrical lens attachment ? ? ? ? ? ? $1 095
TEST TUBE HOLDER.
This holder is a secure method of supporting a fest
tube and enables a number_ of tubes to be easily and
quickly changed. It is attached to the spectroscope
4-4;4ii 4 LI1 by two clamping screws and can be used on models
Nos. 2447, 2449, 2425, 2426, 2458, 2459, 2522 and
2523.
No. 2697. Test tube holder .. ? . $2.95
$950
PRECISE MEASUREMENTS COMPANY Brooklyn 23, New York
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? .1 1, it. I 111... 1..1,1 I I.. 1 I ? All
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Nos. 2435 and 2438 ULTRA VIOLET SPECTROSCOPES.
Declassified
This is a compact spectroscope for the examination of the ultra violet spectrum
Its general design can be seen by the illustration. It has an accurately made
slit, fixed or adjustable, through which the light passes on to a quartz prism,
forming a spectrum upon a. fluorescent screen. The spectrum thus formed is
examined by an eyepiece, giving a magnified image. The eyepiece is provided
with a focussing motion and an eye cup to exclude extraneous light.
Beside the spectrum in the field of view is an illuminated
scale, divided in Angstrom units, so that the wavelength of
any portion of the spectrum under observation can be deter-
mined. The scale appears with illuminated lines and figures
upon a black background, the illumination being obtained
through a window in the instrument by means of the visible
light in the light source under examination, so that no add-
itional source of light for illuminating the scale is necessary.
The spectrum included in the field of view is from 2,000
A. to 4,500 A., which includes a small portion of the
visible light.
The instrument can be conveniently used in the hand, table
stand can be supplied if i equired
This spectroscope has been designed with a view to giving
a particularly brilliant spectrum, thus rendering it easily
used in daylight and with the same ease as a spectroscope
for visual light. It is, therefore, specially useful for rapid
determinations in electromedical and similar establishments
and for industrial workshop use, when a more complicated
apparatus is inconvenient to use.
When a small source of light is being examined, the brilliancy of the spectrum
can be increased by using a cylindrical lens attachment (page 12), thus making
it unnecessary to hold the spectroscope close to the source of light.
No. 2435. ultra violet spectroscope, in case .. 109.50
No, 2438. ultra violet spectroscope with adjustable slit;
in case . . 114.50
PRECISE MEASUREMENTS COMPANY Brooklyn 23, New York
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20
25
30
35
46
45
Spark spectrum of zinc
and cadmium as seen in
eyepiece of spectroscope.
_ _ I _ JLL. 11 I _
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What's Ahead?
by LLOYD E. VARDEN
With the coming of high-speed pan
films, and later, color materials for
home processing, photographers were
compelled to struggle through most of
their darkroom chores in absolute
darkness. The once useful dark-green
safelight provided enough light?after
the eye became adapted?to give one
confidence in carrying out the most
intricate of darkroom manipulations
with slower or less color sensitive ma-
terials. Today, though, when a high-
speed pan or color film jams, for ex-
ample, while loading it into a develop-
ing reel, about all that can be done is
to start from scratch and hope for the
best. To turn on a safelight is inviting
disaster.
Seeing in the dark
During the war, reports leaked out
that soldiers had been given devices
enabling accurate rifle fire in complete
darkness. The secrecy was not entire-
ly warranted, because as early as 1934
disclosures had been made in the sci-
entific literature on converting invisi-
ble infrared radiation to visible light.
The now well-known snooper scope
and sniperscope employed this princi-
ple. An infrared searchlight, which the
enemy could not see, "illuminated"
the field of observation. The scope con-
tained a lens system that projected an
infrared image of the scene onto the
photo-cathode of an electrostatic im-
age tube. Electrons emitted from the
infrared sensitive surface were then
focused by the tube onto a small
fluorescent screen, producing a visible
image that was observed through a
magnifying eyepiece. The principle in-
volved is made clearer in Figure 1.
It is obvious that an instrument of
such novelty should find peace-time
applications. Immediately after the
war, for example, Pavelle Color Inc.
purchased a surplus military infrared
Fig. 1. above: Invisible radiation is projected by infrared searchlight (1) onto scene
(2). reflected to lens (3) and onto infrared sensitive photo-cathode (4). Electron
beam is focused electrostatically by image tube (5) which gets its power from (6).
Fluorescent screen (7) shows image, seen through viewing lens (8) by human eye (9).
telescope in the hope that it could be
adapted for "seeing" in the pitch black
darkness of color processing dark-
rooms. The instrument was relatively
small, and was easily refocused for
close-up viewing. It operated from an
ordinary 115 volt electric line, and pro-
vided an amazingly brilliant image
when the area under observation was
illuminated by a 150 watt tungsten fila-
ment lamp, housed to emit radiation
only through a Wratten No. 87 infra-
red filter. Sufficiently fine detail could
be observed to carry out nearly any
darkroom operation. (Written instruc-
tions on a sheet of paper could be read
with ease.) It appeared as though the
difficulties that arise from working in
complete darkness would soon be a
thing of the past.
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II III 1 I 1 111_1
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Fig. 2, below: Infrared source (1) projects beam through infrared filter (2) onto
sheet of film to be observed (3). Rays are reflected through infrared filter (4). lens
(5). and onto phosphor-coated surface of rotating cylinder (6) which has previously
been exposed to rays from ultra-violet source (7) in reflector (8). Image thus be-
comes visible to human eye (9). This is principle of Tuttle's device.
Fundamental problems involved
The application of the infrared
image tube for general photographic
purposes is restricted by at least two
fundamental problems. First, many
photographic emulsions, after expos-
ure in the camera, exhibit an image
reversal when exposed to infrared
radiation. This is known as the Her-
schel effect.
The first of these problems could no
doubt be overcome by limiting the
viewing times in the darkroom to a
minimum, or by reducing in other
ways the amount of infrared radiation
reaching the film.
A different approach
Another approach to seeing in the
dark was recently described by C. M.
Tuttle of the Eastman Kodak Co. in
U. S. Patent 2,521,953. Tuttle makes
use of an infrared source and phos-
phorescent substances, but the visible
image is formed in a manner different
from the image tube. He takes advan-
tage of the fact that infrared radiation
can be employed to stimulate the
fluorescence of a previously excited
phosphor, i.e., one that has been ex-
posed to ultraviolet radiation, for ex-
ample, so that the brightness of the
fluorescence increases with the amount
of infrared the phosphor receives. Or,
by proper choice of the phosphor, the
infrared can be used to quench, or "put
out" the fluorescence previously pro-
duced by an ultraviolet source. Now,
by means of a rotating phosphor-
coated surface enclosed in a box with
an ultraviolet source, and with a lens
on one side and a viewing hole on the
opposite side, it is possible to illumi-
nate a light sensitive material with in-
frared and view its visible fluorescent
image. One such device described by
Tuttle for inspecting film during
manufacture is shown in Figure 2.
The rotating phosphor-coated surface
passes the ultraviolet source where it
is excited. It then passes the infrared
image formed by the lens where, de-
pending upon the phosphor used, the
fluorescence of the rotating surface is
stimulated or quenched according to
the amount of infrared radiation strik-
ing any particular point. The image
produced remains on the surface long
enough to be viewed through the peep-
hole before reaching the ultraviolet
source again. With one type of phos-
phor a negative image is produced, and
with the other, a positive image. A de-
vice based on this principle could be
made fairly compact and at much less
cost than one incorporating an elec-
tronic image tube. Whichever ap-
proach is taken, there is no reason why
photographers cannot expect to "see
in the dark" in the darkroom of the
future.?THE END.
Reprinted from
MODERN PHOTOGRAPHY
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I I1 I
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F"
ARMY PLANS TO BUY
6,918 `SNIPERSCOPES'
WASHINGTON, ?The
night eyes" of the rifleman, the
electronic "sniperscope" that is
?credited with causing 30 per cent
, of all enemy casualties in the Oki-
nawa campaign, is being made a
f standard item of Army equipment.
t. Army sources disclosed today
I that'the field forces were so im-
rresded with the efficacy of the
auxiliary weapon that enables the
infantryman to "see" the enemy
/
through darkness that units in all
the .krmy's ten divisions would be
equipped with the device.
1 Included in the Army's budget
requests now before Congress is an
$8,654,418 item for the purchase of
6,918 "sniperscopes" at a cost of
$1,251 each. How many of the de-
vices are already in use is con-
sidered secret information.
The "sniperscope" consists of an
electronic telescope that is mount-
ed on the standard Army .30-cali-
bre carbine. Wiring runs from a
portable power pack carried in a
Iharnessed knapsack on the soldier's
back.
Operating under cover of dark-
ness, the rifleman points the
"sniperscope" and his gun sights
toward. a spot whence a sound has
come. By switching on an infra-
red spotlight, he makes rays scan
the territory. These are reflected
from the target, picked up by the
i telescope and transformed into an
image across the sights of the rifle-
La.4
mn.
-111111110
Uranium Test Kit designed
to fit in your pocket, will make a positive
identification in five minutes. Chemical
bead is formed on wire, fused with
crushed ore, then examined for lemon.-
yellow fluorescence under ultra-violet
light.
$4.95
VIBRATOR
IGNITION COIL?This miniature high volt-
age coil provides high output for snooper-
scope operation.
No. 2444 POCKET DIFFRACTION SPECTROSCOPE.
This is a very convenient pocket spectroscope for general purposes and students,
use, having a dispersion of 20?. The slit is of a fixed width, protected by a glass
cover to prevent dust from entering. An adjustment for accurately focussing
the spectrum is provided.
No. 2444. Pocket spectroscope, in case
Our Price $12.50
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I.. II J 1,11.1 !ILJ ?ih 1-1 Ili
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Rush Order Blank
Name
Date
Street Address or Rural Route Box No
Town Zone
State
QUANTITY
DESCRIPTION
PRICE
PER
AMOUNT
MINIMUM ORDER 50 CENTS. MATERIAL IS SHIPPED POSTPAID TO ANY
POINT IN U. S. A. UNLESS MARKED OTHERWISE. CANADIAN AND FOREIGN
ORDERS ADD 10% TO COVER COST OF ADDITIONAL PACKING. REMIT BY
MONEY ORDER OR POSTAL NOTES.
PRECISE MEASUREMENTS COMPANY
942 Kings Highway, Brooklyn 23, New York
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p (0
(Z 61:11.../LAdt?-?A:A.
the Book of
Snooperseopes
Ingenious infra-red
viewing device lets
you see in the dark
PRECISE MEASUREMENTS CO.
942 KINGS HIGHWAY
BROOKLYN 237 N. Y.
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I
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An Infrared Imacc Tubc
and its Military Applications
by
G. A. MORTON AND I. E. Ftovy
Reprinted from RCA REVIEW
September 1946, Vol. VII, No.3
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--
Ii I
J." 1
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AN INFRARED IMAGE TUBE AND ITS MILITARY
APPLICATIONS*t#
BY
G. A. MORTON AND L. E. FLORY
Research Department, RCA Laboratories Division.
Princeton, N. .1.
Summary?The military value of the security obtained by the use of
infrared for nocturnal vision was recognized even before the entry of the
United States into World War II. A program for the development of in-
frared viewing devices employing electron image tubes was consequently
set up by the National Defense Research Committee. Before the close of the
war a number of types of infrared telescopes had be.en manufactured in
quantity and had seen service in fairly large numbers.
The 1P25 image tube is the essential element in the infrared electron
telescope, and serves to convert the invisible infrared image into a visible
image. The tube contains a semi-transparent photocathode which is proc-
essed to be sensitive to infrared radiation, and an electron lens for imaging
the electrons from the photocathode onto a fluorescent screen which becomes
luminous upon bombardment by electrons. When an infrared image is
focused on the photocathode, a visible reproduction of this image is formed
on the fluorescent screen.
Basically, the infrared telescope consists of the image tube, an objective
for forming the infrared image on the photocathode and an ocular for view-
ing the reproduced image. Associated with the telescope is a battery oper-
ated vibrator power supply which furnishes the 4000 to 5000 volts and the
several intermediate voltages required by the image tube.
A variety of types of telescopes was developed and produced for a
number of different applications. These included a signalling telescope
employing a large aperture reflective optical system as objective, the
Sniperscope which is a carbine-mounted telescope and infrared source per-
mitting aiming and shooting in complete darkness and the Snooperscope
composed of the same infrared units mounted on a handle for short range
reconnaissance work. Binocular telescopes, helmet-mounted driving and
flying instruments, long-range reconnaissance units and other special night-
seeing devices were also developed in the course of this project.
F.4VEN before the entry of the United States into World War II,
it was recognized that many military operations would require
the secrecy afforded by complete visual darkness. Therefore,
the National Defense Research Committee, under Army and Navy
directives, undertook the development of infrared viewing devices em-
ploying electron image tubes and an investigation of the applications
*.Decimal Classification: R138.31 x R800 (621.375).
1. This paper is based in whole or in part on work done for the National
Defense Research Committee under Contracts OEMsr-169 and OEMsr-440
with Radio Corporation of America.
# Reprinted from RCA Review, September, 1946.
308
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1 H
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INFRARED IMAGE TUBE 309
of such devices. This work was carried out by these laboratories.
A variety of infrared telescopes was developed suitable for different
tasks and a number of types saw considerable service during the war.
Among the most widely used were the Navy infrared signalling equip-
ment and the Sniperscope and Snooperscope procured by the Army.
Figure 1 illustrates an infrared telescope, while Figure 2 shows the
laboratory prototype of the Sniperscope.
Basically, all of these telescopes consist of an objective for forming
an infrared image of the scene being viewed upon the photosensitive
cathode of the image tube, the image tube itself, and an ocular for
viewing the reproduced image. The general form of the electron tele.
Fig. 1?Infrared telescope.
scopes using refractive and reflective optics is shown schematically
in Figure 3.
The fundamental component of these infrared telescopes is the
electron image tube. This tube consists of a semi-transparent photo-
cathode processed so that it has high sensitivity in the infrared por-
tions of the spectrum, a fluorescent screen and an electron optical
arrangement for focusing the electrons onto the screen.
In undertaking the design of these instruments and tubes, the re-
quirements of mass production as well as those relating to the particu-
lar application, were taken into consideration. As a result, the U. S.
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ELECTRON TUBES, Volume II
Fig. 2?Laboratory prototype sniperscope.
Armed Forces were able ,to obtain these instruments in far larger
quantities than could either the Germans or the Japanese whose in-
struments were not suitable for quantity production*.
INFRARED TELESCOPES
OBJECTIVE LENS
IMAGE TUBE
SCHMIDT OBJECTIVE
CORRECTOR
PLATE
OCULAR
TO POWER SUPPLY
SPHERICAL MIRROR
PLANE MIRROR IMAGE TUBE.
Fig. :3?Schematic diagram of two types of infrared telescopes.
OCULAR
TO POWER
SUPPLY
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INFRARED IMAGE TUBE 311
TILE IMAGE TUBE
An investigation of electron imaging dating back to the early 1930's
had resulted in successful image tubes.' ' However, the requirements
placed on an image tube for military applications were so very different
from any heretofore encountered that it was necessary to re-examine
the entire subject again.
The most important considerations were, of course, sensitivity of
the tube and perfection of the image. These are properties of the
activation, phosphor efficiency and electron optics, and will be discussed
in greater detail. A second very important consideration was that the
tube be?of such a form that it could be produced quickly in fairly large
numbers. Finally, it should be so designed that a single type of tube
could be used for all of the various applications envisaged.
Tube dimensions selected as being the best compromise between the
very small size which would be desirable for portable instruments, and
the larger tube suitable for fixed units, were 41/2 inches length and
17/8 inches maximum diameter. This size was found convenient from
the production standpoint, and useful in a wide variety of instruments.
Consideration of power supply design, cable insulation and tube sta-
bility dictated an overall voltage range of 4000 to 6000 volts.
The first decision which had to be made concerned the most practi-
cal way of imaging the electrons from the cathode onto the fluorescent
screen. There are essentially three systems which may be used, namely:
(1) uniform field between cathode and screen;
(2) magnetic lens; and
electrostatic lens.
The first was rejected because of the close spacing betweer oathode
and screen and high field strength necessary in the vibinity of the
cathode. This makes the activation difficult and the tube prone to cold
discharge. Also, the image produced in this way is erect where prefer-
ably it should be inverted. Magnetic focusing was also rejected from
the standpoint of weight and complexity, and because of the difficulty
of obtaining an inverted image.
An electrostatic lens system is capable of a sharp, clear image over
a wide range of magnifications. The image is inverted making it un-
necessary to use an inverting ocular for viewing the reproduced image.
It is necessary to curve the photo cathode in order to produce an un-
distorted image over a large angular field. Where a reflective optical
system is used as objective, the curvature of the cathode can be made
V. K. Zworykin and G. A. Morton, "Applied Electron Optics", Jour.
Opt. Soc. Amer., Vol. 26, No. 4, pp. 181-189, April, 1936.
2 G. A. Morton and ENG. Ramberg, "Electron Optics of an Image Tube"
Physics, Vol. 7, No. 12, pp, 451-459, Dec., 1936.
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312 ELECTRON TUBES, Volume II
to match that inherently present in the image surface of these optics.
It is, however, sometimes necessary to use an optical field corrector
lens when an ordinary refractive objective is employed, if the field of
view is to be flat. However, since the electrostatic lens is also free
from the objections mentioned in connection with the magnetic and
uniform field systems, it was selected as the most satisfactory for the
purpose.
The magnification of the image tube has an important bearing on
its performance. This is because the brightness of the reproduced
image varies inversely with the square of the magnification. Thus, if
a telescope with a given overall.magniflcation employing an image tube
IMAGE TUBE
(IP25)
ELECTRON LENS
FLUORESCENT SCREEN
600 V.
CATHODE
4000V.
SIMPLE OPTICAL ANALOGUE
Fig. 4?Schematic diagram of 1P25 Image Tube.
with unity magnification and an X5 ocular is compared with one using
an image tube with magnification and an X10 ocular, the image in
the latter will be four times brighter. However, for a given size of
image tube and angular field of view, the magnification cannot be de-
creased indefinitely because ,as the power of the ocular increases the
size of the exit pupil decreases until a poin t is reached where the pupil
of the dark adapted eye is not filled. Beyond this point, the brightness
of the retinal image does not increase with decreasing magnification
of the image tube. For many applications, it is also essential that the
exit pupil be much larger than the pupil of the eye, so that the ob-
server's eye ,does not have to be located too exactly with respect to the
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INFRARED IMAGE TUBE 313
instrument. Experiment showed that for a tube the size of the image
tube under discussion, the magnification should not be less than one-
half. Figure 4 illustrates schematically the construction and action of
the image tube adopted.
ELECTRON OPTICAL CONSIDERATIONS
The electron optical system of the image tube consists essentially
of a strong main lens as the principal imaging means and a series of
relatively weaker correcting lenses between the cathode and main lens.
The potential distribution along the axis of the tube is shown in the
upper portion of Figure 5. Two electron paths, one of an electron
CORRECTING
LENSES
MA IN
LEN'S
G,
G.
G.
Fig. 5?Potential distribution and electron paths in the Image Tube.
originating from the cathode on the axis of symmetry with radial
initial velocity, the other originating off the axis with no initial velocity,
are illustrated in the lower part of the figure. These two paths are
sufficient to determine the first order imaging properties of the system.
A detailed theoretical study of this type of system le4e5 to the
following conclusions:
(1) Curvature oi the image field and pincushion distortion can
only be eliminated by the use of a curved cathode (or a radial potential
gradient on the cathode).
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314 ELECTRON TUBES, Volume II
(2) Curvature of the image surface and astigmatism limit the
off-axis definition.
(3) Chromatic aberration due to the spread of initial velocities of
the photoelectrons establishes the limit of resolution at the center of
the image.
(4) Spherical aberration and coma play a negligible role in limit-
ing the definition.
The radius of curvature of 2.38 inches selected for the cathode was
a compromise between that required for a flat electron. image surface
and optical considerations of the objective. With this Ciirvature very
little pincushion distortion remained, and a definition of 350 lines
(television nomenclature) or better could be obtained near the margins
of the picture.
At the center, the diameter (C) of the circle of cohfusion due to
chromatic aberration is given approximately by:
2 m V/E (1)
where E is the gradient near the cathode and V the' initial electron
energies in electron volts. Evaluating this from the gradient known
to exist in the tube and from the initil velocities expected near the
infrared threshold, the limiting definition at the center, is 2000 or more
lines. Definitions of 1000 lines were realized in laboritory tubes, and
of 450 lines or better in production tubes. In general, the difference in
definition between the theoretical estimated definition and that achieved
in practical tubes is due to misalignment of the electrodes, inhomogeni-
. ties in the photo-cathode and granOlarity of the fluoiencent screen.
PHOTO-ELECTRIC CATHODE
The photo-sensitization of the cathode is one of the critical steps
in the preparation of the image tube. Research to date has lead to the
cohclusion that a complex surface involving caesium, oxygen and silver
yields the highest infrared response of any of the surfaces yet studied.
This surface is formed by evaporating a thin layer of silver on the
cathode disk, oxidizing it completely, then adding alternately silver,
caesium and silver while subjecting it to an appropriate thermal treat-
ment. The completed surface is semi-transparent so that, when illumi-
nated from the outside, electrons are emitted from the inner surface.
The photoemission from a well activated surface of this type will be
30 to 50 microamperes per lumen for whole light (iiisible + infrared)
from a. tungsten source at a color temperature of 2870 degrees Kelvin.
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INFRARED IMAGE TUBE
Figure 6 illustraths the spectral response of this type of emitter.
315
FLUORESCENT SCREEN
The requirements of the fluorescent screen are the following:
(1) It must have a high efficiency of conversion of electron energy
into visible-light of a color suitable for scotopic vision.
(2) It should have a fine grain structure capable of giving high
definition.
(3) Its time 'constant must be short so that moving images do not
blur.
(4) It should be inert to the chemical action of caesium.
Synthetic willemite was found to satisfy these requirements fairly
well, although its' phosphorescent decay time is somewhat longer than
60
50
O 40
a.
UI
1/1
CC 30
6.1
? 20
-1
UI
CC
JO
? .2 Lo LI 12 1.3 14
WAVELENGTH (MICRONS)
Fig. 6?Spectral response of 1P25 Image Tube.
might be desired-,.. In spite of its shortcoming as far as persistence is
concerned, it was selected as the phosphor most suitable for the 1P25
because of its availability and ease of handling together with its
chemical stability.,
The efficiency' of this phosphor in the vicinity of 5000 volts is be-
tween 1 and 3 candles per watt. Its color is green or yellow-green which
is quite satisfactory from the standpoint of scotopic vision. With a little
care, the grain 'and aggregate size can be made small enough so that
the screen does not limit the definition of the image. The decay charac-
teristic of the material cannot be expressed by a single time constant.
However, for the brightness involved in such applicatiohs of the tube
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316 ELECTRON TUBES, Volume II
as night driving, reconnaissance, and sniperscopes, the relation:
g=go,-60t (2)
where t is the time in seconds after excitation ceases and Bo is the
brightness at t o is entirely adequate. The expression for phos-
phorescent decay indicates that the image brightness falls to 10 per
cent of its initial value in 0.04 secs. While rapid enough for most
purposes, it causes some loss in definition for, rapidly moving objects.
At very low brightness levels, the decay becomes less rapid than ? is
indicated by this expression. This long low-level afterglow is of con-
sequence in the detection of an infrared marker and signal light near
the visual threshold.
Fig. 7-1P25 Image Tube.
IMAGE TUBE PERFORMANCE
The performance of the 1P25 image tube may be summarized as
follows: The light output per lumen of Tight incident on the photo-
cathode, or conversion, is in the neighborhood of 0.5 to 1 lumen. In
conjunction with an infrared filter, the conversion is reduced by the
corresponding filter factor. It has been customary to express this
filter factor in terms of the ratio of the image-tube response for whole
light from a given incandescent source at color temperature 2870 de-
grees Kelvin to the response from the same source when filtered.
The central definition of the image is 450 lines or more and the
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INFRARED IMAGE TUBE 317
peripheral definition 300 lines. This definition is such that for most
brightness levels encountered in practice, the eye rather than the
instrument is the limiting element.
A photograph of the finished tube is shown in Figure 7.
During the later stages of the research program, a number of new
types of tubes were developed to meet special problems. One of these
was a single-voltage tube, contained in an envelope identical to that
of the 1P25, but requiring no intermediate or focusing voltages. This
tube is interesting in that it employed an electron optical system with
an unconventional departure from circular symmetry. A second tube
operated at an overall-voltage of 16 kilovolts employing a multiple lens
anode.
INSTRUMENTS EMPLOYING THE 1P25
During the course of the investigation, many different types of
infrared instruments were developed employing the image tube. The
number is so large that only a small fraction of them can be described
in this paper. Therefore, a few representative instruments have been
selected which will be described ahd their performance indicated.
Signalling Telescopes
One of the widest and at the same time most exacting use of the
electron telescope is for the observing of infrared signal and marker
lights. Here, since the object observed is an unresolved luminous point,
the consideration,s involved in determining the sensitivity of the
instrument are quite different from the case of an extended image.
The two primary optical factors are the area of the objective and the
magnification, while for the image tube the conversion and background
only are involved. It will be noticed that the f-number of the objective
and magnification of the image tube do not affect the sensitivity. How-
ever, if a lens with a large f-number or an image tube with high
magnification is used, the angular field of view will be small which is
undesirable for a marine signalling or search instruments. For these
reasons the signalling telescope was designed with an objective having
a short focal length and.large aperture. The only practical way of
achieving such a system is by the use of reflective optics, as illustrated
in the lower part of Figure 3. The corrector plate and spherical mirror
were of transp. arent plastic, assembled as a unit in a plastic barrel.
The system was arranged so that the image was folded back by means
of a plane mirror onto the cathode of the image tube. The focal length
of this objective was 2.4 inches and its effective f-number was about
0.9. The image on the fluorescent screen was viewed through an XII
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318 ELECTRON TUBES, Volume 11
ocular. A hemisphere, which was an integral part of the image tube
bulb, was a component of the ocular system. The telescope and power
supply were assembled in a light, weatherproof and hermetically sealed
magnesium casting. A discussion of power supplies for this type of
instrument will be postponed until a later section.
A much larger reflection-type telescope was also developed having a
7-inch focal length and approximately the same effective numerical
aperture. This instrument was very much more sensitive as a signal-
ling telescope but had a much smaller angle of view. Because this
instrument was also designed for reconnaissance, its optical focus was
made variable through an adjustment which moved the plane mirror
in and out.
Reconnaissance Telescope
With the exception of the large reflective-type telescope mentioned
in the preceding paragraph, the reconnaissance instruments were in
general of the small portable variety. In order to give them greater
depth of focus than could be obtained with a reflective optical system,
these telescopes employed refractive optics with f-numbers down to
about 2.0. With an f/2.0 lens and an image tube having a conversion of
1.0 the ratio of brightness of the image of an object illuminated with
whole light as seen through the telescope to brightness as seen directly
is about 0.10. This ratio is reduced by the appropriate filter factor
when a filtered source is employed.
In their simplest form, these instruments consist of a barrel (usu-
ally of mu-metal or other high permeability alloy for a shield) contain-
ing the image tube, to which are affixed the objective and ocular, both
in focusing mounts. Tests indicated that objective focal lengths in
the range 21/2 to 31/2 inches and ocular magnification of X8 to X12
were most satisfactory. For example, when used as the basis of a
driving telescope, as will be discussed below, an instrument with a
21/2-inch objective and an X8 ocular giving an overall magnification
of unity and a 24-degree field of view gave best results, while for
devices such as the Sniperscope and Snooperscope a 31/2-inch focal
length objective and a X8 or X12 ocular were to be preferred.
Power for the image tube was supplied through a three wire, in-
sulated cable providing ground, the overall voltage and the variable
focusing voltage. A resistance voltage divider at the image tube
socket provided the other voltage steps for the 1P25.
Other instruments were designed with the power supply an integral
part of the telescope. One unit employs a 21/2" focal length f/2.0 plastic
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INFRARED IMAGE TUBE 319
objective and an X12 ocular. A model is illustrated in Figure 8. Its
size and weight is only about one third that of the telescope shown in
Figure 1.
For general purpose observation, these simple in-line monocular
telescopes served as very useful tools. For example, this type of in-
strument was frequently carried by an observer during night driving.
Also, it was used to supplement the large reflective-type telescopes as
general orientation instruments, and for many other supporting opera-
tions. Under these circumstances, the illuminator providing the in-
frared radiation was a separate unit over which the user of the tele-
score had little or no direct control.
Fig. 8?Experimental telescope.
Frequently it is advantageous to have a portable light source to
use in conjunction with the telescope. Therefore, a study was made of
instruments involving source-telescope combinations. In particular,
two instruments of this class were developed, namely, a monocular
telescope and a light source mounted on a handle for relatively short
range reconnaissance (see Figure 9) and a similar telescope and source
mounted on a carbine in such a way that the telescope could be used
for aiming in complete visual darkness. These instruments were
christened Snooperscope and Sniperscope respectively and were later
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320 ELECTRON TUBES, Volume II
named Molly and Milly by Members of the Armed Forces.
The telescopes used in the laboratory prototypes of these units were
essentially the same as the monocular telescope described in earlier
paragraphs. The objectives were 31/2-inch focal length f/2.0 lenses
while an X8 ocular was used for viewing the screen. A chevron was
placed on the surface of the field-corrector lens to serve as the aiming
index for the Sniperscope. This chevron was accurately aligned with
the direction of fire of the piece. By placing the aiming index at the
objective, distortion or deflection of the electron image had no effect
on the accuracy of aiming.
Tests were made to determine whether the telescope, including the
image tube, was sufficiently rugged to withstand the rough usage in-
volved in this application. No particular difficulties were encountered
Fig. 9?Laboratory prototype Snooperscope.
in the case of the Snooperscope. In the Sniperscope, a certain percent-
age of tubes were found to fail as a result of the shock of firing, due
to minute particles of the phosphor becoming dislodged from the fluor-
escent screen and settling On the lens electrodes and causing flashing
in the tube because of cold discharge. This made it necessary to shock-
test production tubes before employing them for this purpose.
The selection of the size and form of light source was a result of
compromises in a number of directions. These included angular field,
range, operating life for the allowable battery weight, and considera-
tions of security. The source chosen for the laboratory models was a
special General Electric sealed beam lamp with a 12 to 15 degree spread
and a maximum beam candle power of 80,000. Various infrared filters
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INFRARED IMAGE TUBE 321
were used including Corning 2540 heat transmitting glass and the
Polaroid XRX series.
The high voltage power supply and storage batteries were carried
in a knapsack with a cable from it to the instrument carrying both the
image tube voltages and the current for the infrared source. The de-
sign of the power supply is discussed in a later section.
The weight of the telescope and source was about 5 pounds while
the power supply and batteries weighed approximately 13 pounds. The
unit was capable of 3 to 4 hours continuous operation before it was
necessary to recharge the batteries. The Snooperscope and Sniperscope
were manufactured on a fairly large scale, the production design being
carried out by the Engineer Board of the Army for the Corps of
Engineers.
Driving Instruments
In some applications, particularly vehicle driving, it is advantageous
to have binocular vision. It is interesting to note that while the observer
feels a very definite need of being able to use both eyes it makes very
little difference whether or not he has stereovision.
The first experimental driving instruments were in the form of a
single large barrel carrying the objective and eyepiece, and enclosing
an image tube which was much larger than the 1P25. The eyepiece
was so arranged that the virtual image of the fluorescent screen was
at infinity and the observer saw this image with both eyes.
This type of driving telescope was found to be generally quite satis-
factory, but suffered from two serious drawbacks. It was quite large
and occupied considerable space in the vehicle and it was difficult to
use on short turns.
To overcome these difficulties, a small binocular instrument was
developed using two 1P25's. This instrument, illustrated in Figure 10
gave the observer true stereovision. The binocular consisted of a pair
of in-line telescopes mounted parallel to one another by means of hinges
so that the interpupillary distance could be adjusted to fit the user.
In order to obtain satisfactory register of the images seen by the two
eyes, it. was necessary to provide means for moving the two images
relative to one another. This was accomplished by mounting the ocular
lenses in such a way that their axes were slightly displaced with
respect to the axes about which the ocular fittings could be rotated.
When the eyepiece fittings were turned the two virtual images seen
by the observer moved in circles about two different centers. The
points of intersection of these circles are the points of register of the
images.
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322 ELECTRON TUBES, Volume II
Separate focus of the two objectives and two oculars was provided.
The power supply was designed so that the electrical focus of the
two image tubes was also independent.
These binoculars, with a suitable head rest, served as excellent
driving telescopes, when supported on a pivoted arm in front of the
driver. As designed the instrument not only gave the operator use of
both eyes but also permitted true stereovision.
Some experiments were undertaken in helmet mounting the in-line
binoculars. However, even when counterbalanced to neutralize the
forward torque of the instrument, the moment of inertia was rather
high which made it awkward to handle.
To overcome this, an investigation was made on a series of helmet-
Fig. 10?Infrared In-line Binocular.
mounted instruments. Figure 11 illustrates an early right-angle peri-
scopic unit. The results of these tests were so encouraging that the
-development of a light-weight, Z-shaped binocular suitable for night
flying and driving, was undertaken in collaboration with the
Johnson Foundation of the University of Pennsylvania. The completed
instrument is illustrate in Figure 12. The unit was made of aluminum,
and plastic optics were used throughout (except for the ocular lenses)
to reduce the weight to a minimum. The folding was accomplished by
means of plastic prisms. Again, independent optical and electrical
focusing adjustments were provided for the two sides, the electrical
focus being controlled by means of potentiometers mounted at. the
bases of the telescope barrels. Register of the image was effected by
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INFRARED IMAGE TUBE 323
means of a pair of rotatable ring magnets mounted on each barrel
just below an inner mu-metal shield which surrounded the image tube
from cathode to main lens. The resultant field of these ring magnets,
which could be varied in intensity and direction by rotating the rings,
made it possible to deflect the electron images into exact alignment.
These helmet telescopes appeared to be a very adequate solution to
the problem of infrared night driving, and were on the verge of going
into production when the war ended.
Fig. 11?Periscopic Helmet Monocular.
HIGH VOLTAGE POWER SUPPLIES
The 1P25 image tube requires a rather high voltage for its opera-
tion. Since portability was one of the aims of the development, it was
essential that the power supplies be small and operate from a small
primary battery source. At the same time, the battery life had to be
above a certain minimuT if the instrument was to be practical.
The design of a power supply meeting these requirements is pos-
sible only because of the fact that while la 4000 to 6000-volt output is
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324 ELECTRON TUBES, Volume II
required, the actual power needed is very small. The tube itself re-
quires only a fraction of a microampere of current even under bright
light conditions. The total power output required to supply the tube
and the voltage divider necessary for the various focusing electrode
voltages of the 1P25 is on the order of a tenth of a watt.
The only practical available means of converting the low voltage
Fig. 12?Type Z Helmet Binocular.
from the batteries to the high potential necessary to actuate the image
tube is a vibrator-transformer-rectifier combination. A typical vibra-
tor power supply is shown in Figure 13. It differs from the conven-
tional vibrator power units used in battery operated radios, in that,
due to the low power requirement, use can be made of the relatively
high voltage peaks appearing across the primary of the transformer
when the magnetic field collapses as the primary circuit is broken by
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INFRARED IMAGE TUBE 325
the vibrator. In addition the primary is tuned to resonate with the
natural period of the secondary to obtain maximum transfer of energy.
By this method an effective primary voltage of ten to twenty times
the battery voltage is realized. This makes possible a great reduction
in the size of the transformer required.
A standard automobile type vibrator was used because of ease of
procurement. The frequency was of the order of one hundred inter-
ruptions per second and the power consumed was about 0.2 watt. A
conventional rectifier circuit and capacity filter was used employing
the special rectifier described later.
The design of the transformer was necessarily a compromise be-
tween light weight and efficiency. A light-weight transformer with
VIBRATOR
R?il*NO
K- 901414
Fig. 13?Basic circuit of vibrator power supply.
somewhat lower efficiency means a larger battery or shorter battery
life, while a heavier transformer will give a higher efficiency due to
lower core losses. As a result, the optimum transformer is usually a
design unique to the particular application. For an overall efficiency
of 10 per cent, including vibrator power and rectifier filament, at an
output of 4000 volts, the weight of the transformer is on the order of
20 ounces per watt of output. This means that in order to supply one-
tenth watt at 4000 volts a two-ounce transformer would be required at
an input of one watt. At somewhat higher power ouputs the efficiency
may run as high as 20 per cent, since the power taken by the vibrator
and rectifier will be constant.
A typical transformer design may be approximated by making the
following assumptions:
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326 ELECTRON TUBES, Volume II
Vibrator frequency-100 per second
Time of contact?.005 second
Battery voltage-3 volts
Maximum battery current (peak)-3 amperes
Peak output voltage-4000 volts.
Under the type of operation required, the secondary current is
small and most of the power dissipated in losses. Therefore, as a first
approximation the effect of the secondary circuit on the primary may
be neglected except as it affects the resonant frequency.
If the time constant of the primary is made equal to the contact
time, then
?= .005
Since the maximum current is to be 3 amperes and the voltage is 3
volts, the primary resistance is 1 ohm. Consequently,
L = .005 Henries.
If the decay time of the primary current is now assumed to be
one-tenth of the contact time as determined by the resonant frequency
of the secondary to which frequency the primary is tuned, then
A
e = L ?
t
= .005 = 30 volts.
.0005
(3)
Since the peak output is to be 4000 volts, the turns ratio of the trans-
former becomes
4000
= 133
30
To obtain the necessary primary inductance requires about 100 turns.
Thus 13,300 turns will be required for the secondary.
The direct current from the 3-volt battery under these conditions
is about 0.5 amperes with the secondary delivering about 50 micro-
amperes. A core cross section of 0.25 square inch ordinary silicon
steel with a 0.010 air gap was found sufficient.
Since no rectifier of small size and low filament power consumption
was available, a special tube was developed. This tube, shown in Figure
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INFRARED IMAGE TUBE 327
14, is now in production as the 1654 and in the special circuit shown
will deliver 100 microamperes at 5000 volts. ?
A typical example of this form of power supply is shown in Figure
15. This supply delivers 0.15 watts at 4000 volts with an input of one
watt. The total weight including the battery, which will operate the
instrument for 21/2 hours, is 21/2 pounds.
A high degree of stability of the overall voltage is not essential but
the ratio of voltages on the various electrodes must be maintained to
Fig. 14-1654 Rectifier Tube.
keep the image in good focus. The regulation of the power supply is
not important since the load is essentially constant. As a matter of
interest the equivalent resistance of the power supply shown in Figure
15 is approximately 40 megohms.
Since the overall voltage varies considerably as the batteries dis-
charge and since the instruments may be subjected to wide ranges of
temperature, behavior of the components of the voltage divider as
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328 ELECTRON TUBES, Volume II
regards temperature and voltage was a matter of considerable con-
cern. It would be highly desirable to be able to maintain the proper
voltage ratios over the range of temperatures and voltage encountered
in the field. However, this is not always possible and occasional re-
focusing may be necessary although the variations can be greatly
reduced by proper choice of components in order to balance their
characteristics.
All of the available high value resistors (50 megohms or more) show
considerable change of resistance with voltage. The voltage character-
istics of a few of the best-known resistors are shown in Figure 16.
Using dry cells as a source of power, a 2 to 1 change in overall voltage
may be encountered from start to end point. Under these conditions,
it is impossible to maintain focus without adjustment since a 50 per
cent change in voltage represents a change of about 5 per cent in
Fig. 15-5-kilovolt vibrator power supply.
resistance of the best resistor. Therefore, unless compensation can be
provided, it is necessary to refocus as the batteries deteriorate. In the
case of storage batteries, about 10 per cent change in voltage may be
expected over the operating life. This produces a negligible change in
resistance of the No. 5 resistor and no refocusing is necessary.
Most resistors have a high temperature coefficient and in order to
design a voltage divider which will maintain the tube focus independ-
ently of temperature, it is necessary to select components which either
have the same coefficient, so that the ratio remains the same over the
temperature range, or which have coefficients which tend to compensate
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INFRARED IMAGE TUBE 329
for each other. Variation of resistance with temperature for a variety
of resistors is shown in Figure 17.
In making up a divider, many combinations of resistors tending to
compensate are possible. From the curves in Figure 17, two combina-
tions were selected and the characteristics of the dividers plotted in
Figure 18. In both cases, the G3 voltage remained essentially constant
over the entire temperature range, the small variations being in such
a direction as to compensate for the variation in G2. With divider
No. 1 adjusted for focus at 20 degrees Centigrade, the voltage on G2
remains in the region of good focus over the range from ?10 degrees
Centigrade to + 60 degrees Centigrade. Divider No. 2 remains in focus
3;
0
0
co)
cc 0
2
0
CC
0
?20
5
Ui
0 ?30
V
CC
0.
1000 2000 3000 4000 5000
- APPLIED VOLTAGE
Fig. 16?Voltage characteristics of resistors.
from ?40 degrees Centigrade to +75 degrees Centigrade. Therefore,
using storage battery supply and selected components for the voltage
divider, it is possible to build an instrument which will not require
electrical focusing in the field under the range of conditions usually
encountered.
The Type S., supply shown in Figure 19 is an interesting modifica-
tion of the vibrator power supply. This arrangement is similar to the
conventional voltage doubler circuit except that the two halves of the
doubler are brought out separately. In this way, it is possible to place
a voltage divider across one side without disturbing the other. In
these vibrator supplies, the alternating-current wave is non-syrtunetri-
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330 ELECTRON TUBES, Volume II
-40 -30
-20 -10 0 410 420 .30 440
DEGREES CENTIGRADE
?50 +60 +70
Fig. 17?Temperature characteristics of high-valued resistors.
+80
cal, being in the nature of a damped oscillation, so that in the circuit
shown, the voltage across the high voltage section, which is determined
by the first loop of the wave, is about 4000 volts while the voltage in
the opposite section, determined by the second or negative loop, is
about 1000 volts. Therefore, by putting the voltage divider across
+6
+4
42
04
_[
R, 200 MEGS
--E3(G,)
R,
20 MEGS
R, 10 MEGS
RA 1 MEG
G.
11t I MEG
?
DIVIDER 41
R 6 FIG.I7
? =? "9
DIVIDER
R, -6 FIG.I7
R2 =
R, = '4
174, P. STD I MEG
-
DIVIDER ?I
-2
-4
-6
-6
-101-
E.z
-40 -3'0 -20 -10 0 ?10 420 +30 [phone]
Fig. 18?Temperature characteristics of composite voltage divider.
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jaL/3 4760
T?
INFRARED IMAGE TUBE 331
K. 901576
.
( ET -4236)
614 YE L.
Of
ORR
R- 6193
BLUE
30u)
1.0039
.0039
RED
4C,
? BLUE
R.G.193
Fig. 19?Voltage doubler power supply (Type S-2).
4,1MEG.
ME4
only the low voltage section, the desired low voltages may be obtained
without loading down the high voltage section. Another very interest-
ing feature of this circuit is the fact that by introducing resistance in
the tuned primary circuit, the damping of the circuit is increased
which tends to decrease the second or negative loops and thus the low
voltage without appreciably affecting the high voltage. This action is
shown in the curves on Figure 20. This affords a means of varying the
POINT OF FOCUS
OVERALL VOL TAGE
100
RE EiS TANCE O14M5
200 300 400
Fig. 20?Voltage control of type S-2 Power Supply.
500
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332 ELECTRON TUBES, Volume II
focusing voltage by an element in the primary circuit which is a great
advantage from the standpoint of electrical design.
Another power supply of interest was developed for use with the
single voltage tube. With this tube the only load on the power supply
is the actual photocurrent and leakage. By careful design, the entire
load resistance can be made as high as 1010 ohms. Using a relatively
large capacity in the output, the time constant of the circuit can be
made to equal several seconds so that a quite infrequent charging of
the circuit is required. For this purpose, an Interrupter was designed
consisting of an electrically-driven balance wheel having a period of
Fig. 21?Electrical components of pulsed power supply.
about 1/4 second. The design was such that the transformer primary is
open most of the time and is closed for a short time, to allow the current
to build up, and immediately opened. In this way the drain on the
battery is extremely small, the supply operating for as long as 50 hours
on a single size D flashlight cell. A photograph of the interrupter, the
1-ounce transformer designed for the purpose and the special rectifier
described below are shown in Figure 21.
Since the primary power required by this supply is so small, the
power taken by the usual rectifier filament becomes very large in com-
parison. Consequently, a new type "filamentless" rectifier was developed,
known experimentally as the KR-31.
This rectifier depends for its action upon a gas discharge in Helium,
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INFRARED IMAGE TUBE 333
Neon, or other inert gas at about 0.5 millimeters pressure. The cathode
is an aluminum cup, mounted so that its closed side faces the anode.
The anode is a nickel rod or tube, over which is fitted a woven fibre-
glass sleeve. The entire anode is covered with the fibreglass; the sleeve
fits down over the glass seal at one end and is closed by fusing the
glass at the free end.
The peak inverse voltage of the KR31 is 6000 volts and the for-
ward breakdown voltage is 300-600 volts. The peak current may be
several milliamperes but the allowable average current is low. In the
applications for which the tube was designed the average current is
under 10 microamperes. An average current of 50 inicroamperes may
not be exceeded except for very short periods due to sputtering and
clean-up of the gas.
This tube has not been put into production and is not available
commercially.
The power pack for the Snooperscope and Sniperscope involved
some special considerations. A 6-volt, 25-ampere-hour storage battery
was used to operate the infrared source so the power required to oper-
ate the high-voltage power supply was a negligible drain on the battery.
It was necessary to silence the vibrator to a surprisingly high degree
since the most obvious uses of the instruments were under conditions
of extreme quiet and where the utmost in secrecy was essential. The
usual rubber-mounted automobile radio-type mounting is effective for
damping out the high frequencies, but the fundamental vibrator fre-
quency (100 cycles) is not sufficiently suppressed. One method used
in experimental models was to suspend the mounted vibrator by two
flat spiral springs of at least one turn, coiled around the vibrator can,
the inner ends being fastened to the vibrator can and the outer ends
to the power supply chassis, or box. By proper choice of spring thick-
ness, a period of only a few cycles per second can be obtained with
sufficient stiffness to support the vibrator adequately. By this means
it was possible to silence the vibrator so that the user himself could not
detect the vibration. Another method used, with some increase in bulk,
was the addition of one or more stages of sponge-rubber cushioning
around the usual vibrator can.
The type MA4, high-voltage image tube raised some special prob-
lems in power supply design. The overall voltage required is on the
order of 15 to 20 kilovolts and in addition, a number of intermediate
voltages are required. These intermediate voltages, particularly those
over 4000 volts are difficult to obtain efficiently by conventional means
because of the relatively large power which would be wasted in a
voltage divider of sufficiently low resistance to be stable. Also, it is
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334 ELECTRON TUBES, Volume 11
possible to obtain higher voltages from the previously described power
supplies only by increasing the flux in the transformer. This in turn
can be accomplished only by increasing the primary power, necessi-
tating larger transformer and batteries. Lastly, if a conventional
power supply is used, a rectifier tube capable of withstanding 20 to 30
kilovolts inverse voltage would be necessary. This type of rectifier is
not available in small size and low filament power. Consequently, a
cascade type (voltage-adding) power supply was designed which over-
came most of the objections and automatically provided the necessary
four steps of high voltage without a voltage divider.
A schematic diagram of the S-5 power supply making use of this
circuit is shown in Figure 22. As can be seen, this supply is made up
of four rectifiers which are essentially in parallel for alternating cur-
AMPA44101-
PI.04 TO
BATTERY
VIBRATOR.
K..84749
24. .45
TR An5FOR wIER.
401574
? OOLA F
.002 .004
A F F
"44-Twrff-'4
G7.0
.004
AF
I
.004 ? 004
F
TO
SoCWIT
Fig. 22?Circuit of voltage quadrupler power supply (Type S-5).
rent. The direct-current voltages developed across the rectifiers, how-
ever, are added by means of the resistors which connect the anode of
one rectifier to the plate of the next and thus place ail the rectifiers in
series for direct current. These resistors offer much higher impedance
to the alternating current than do the capacitors so they do not affect
the parallel alternating-current connection. Any number of stages may
be cascaded in this manner,, provided, of course, that the transformer
will deliver the proper voltage to all the rectifiers in parallel. Four
stages were chosen in this case because four steps of voltage are neces-
sary for operation of the MA4 tube. The lower voltages required for
the tube are obtained in the usual way by a voltage divider across the
first section of the power supply. A thermionic rectifier (1654) is used
in this stage in order to supply the divider current but the following
stages make use of KR31 gas rectifiers, thus eliminating the need for
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 iiH H
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INFRARED IMAGE TUBE 335
filament supply circuits, with a high degree of voltage insulation. The
current drain at the high voltages is very low so that the voltages
shown are obtained with a total battery current of only 0.4 ampere at
2 volts. A photograph of the power supply is shown in Figure 23.
The chief problems in connection with this supply are leakage and
corona. These must both be kept to a minimum since the internal re-
sistance of the puwer supply is quite high (approximately 109 ohms at
the 16-kilovolt tap). Leakage can be minimized by use of high-quality
insulation and protection from humidity. Hermetical sealing, or other
provisions for drying, are essential with this type of voltage supply.
Fig. 23-16-kilovolt voltage quadrupler power supply.
Corona can be prevented by eliminating all sharp edges at the high
voltage connections or by coating with a closely-adhering insulating
material such as wax.
CONCLUSION
The above discussion stresses only the military application of in-
frared imaging equipment. There are, however, a number of peacetime
uses for these instruments. Among these applications are their possible
value in police work, their use in the field of medicine, the viewing of
the usual types of photographic film during processing and production
and for the inspection and control of a number of other industrial and
scientific processes where visible light is undesirable.
In closing, the authors wish to express their appreciation to Dr.
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336 ELECTRON TUBES, Volume II
V. K. Zworykin, Director of Electronic Research, for his advice and
encouragement during the course of this development and also their
recognition of the contribution made by Dr. J. E. Ruedy, G. L. Krieger
and Dr. P. Rudnick to this project. Credit should go to Dr. L. B.
Headrick, Miss H. C. Moodey and Dr. R. B. Janes of the Lancaster
plant for work on the production design of the image tube.
As an interesting example of the effectiveness of the infrared
devices described in this paper, two illustrations of a war street scene
at night are included below. The upper picture shows the scene
as viewed by the unaided eye. The lower picture shows, in the circle,
the details of the scene when viewed by the infrared devices.
The Manager, RCA REVIEW
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Home= Built
Snooperseope
Ingenious infra-red viewing device lets
you see in the dark
DURING wartime, man's inability
to see in the dark can often
mean the difference between life
and death. This is particularly
true of scouts, patrols, night drivers,
and flyers. Since visible light makes an
excellent target for the enemy, mili-
tary 'forces began experimenting with
infra-red rays as aids to nocturnal
vision when visible light is not per-
mitted for reasons of security. Many
types of infra-red telescopes were de-
veloped as the direct result of this need
for invisible illumination.
The sniperscope (an infra-red light
source and telescope mounted on a car-
bine to permit the soldier to locate and
shoot the enemy while both are in total
darkness) and the snooperscope (an
infra-red light source and telescope
used for short-range observations) are
perhaps the most well known of these
developments. Other infra-red instru-
ments include helmet-mounted driving
and'flying binoculars, and blackout sig-
naling devices.
The infra-red telescope is designed
around an infra-red image converter
tube which transforms invisible infra-
red rays to visible light. Several types
, of image converters were developed.
The American forces used equipment
built around the RCA 1P25 infra-red
image tube. This tube has a cathode
which emits electrons in proportion to
the amount of infra-red light falling
on it. Additional electrodes within the
tube focus the electrons on a fluores-
cent screen. Thus the image falling on
the cathode is focused on the screen
without scanning devices. This tube,
described in detail in the September,
1946, issue of RCA Review, requires
By HAROLD PALLATZ
voltages of 15, 100, 600, and 4,000 for
proper operation.
The British developed a simplified
infra-red image converter tube requir-
ing a single source of 4,000 to 6,000
volts for its operation. This tube, type
CRI 143 or CV 147, is currently avail-
able on the surplus market and is used
in this experimental snooperscope.
The parts for this snooperscope?a
CRI 143 or CV 147 infra-red image
converter tube, a 4,000-volt, low-cur-
rent power supply, two infra-red fil-
ters, and a light source?are easy to
obtain.
The power supply
For indoor operation, a 4,000- to
6,000-volt neon-sign transformer oper-
ates the tube satisfactorily. Rectifica-
tion is not necessary unless the objects
under observation are in motion. (Ap-
plication of the image tube as a strobo-
scope is the subject of a patent appli-
cation made by the author.)
A portable 4,000-volt power supply
designed for use with this snooperscope
is shown in the photograph and in
Fig. 1. This efficient supply needs to be
turned on only momentarily to charge
the 0.1-?f, 6,000-volt capacitor. The
snooperscope works for several minutes
on the charge, and thus it can be op-
erated for long periods without notice-
able battery drain.
The high voltage is supplied by a
model-airplane ignition transformer
with a vibrator to interrupt the pri-
mary current. The vibrator, not :visible
in the photograph, wits removed from
a small buzzer and mounted just above
the core at one end of the transformer.
A small buzzer can be inserted in series
Reprinted from Radio Electronics
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I I. J1 I .I iii.
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former if desired.
The rectifier tube is a 1B3-GT/8016.
When the power supply is turned on,
the current drain drops the voltage of
each cell to approximately 1 volt;
therefore the 1B3 was connected in
series with a 1-ohm resistor across two
cells. (A 3Q5, with its plate and screen
grid tied together and control grid
floating, might do the job just as well
and would use less filament current.
See the battery-operated, high-voltage
supply described in the article "Build
This Geiger Counter," in the Septem-
ber issue of Radio-Electronics.?Ed-
itor)
1133-GT/8016
DPST SW 2 7
L7pc_.1
.25/600
?1E?
FROM OLD
BUZZER,
4K \/'
0+
7.7
1.5V HI IC NSIO I.
3 No D BATTS LEAD
MODEL PLANE
ON COIL
Fig. I?Miniature high-voltage power supply.
The power supply was constructed in
a plastic ice-box dish and fitted with
insulated binding posts. Avoid contact
with the output of this power supply
or a rather uncomfortable shock may
result. The capacitor remains charged
for some time after the supply is turned
off, so be careful. (It might be wise
to shunt the output terminals with two
or three 47,000-ohm resistors in series
when the supply is not being used.?
Editor)
Assembling the snooperscope
The snooperscope is constructed as
shown in Fig. 2. The image converter
is mounted in a plastic drinking cup
3% inches high and 2% inches in
diameter. The optical system depends
on the requirements for the snooper-
scope. We used a double-lens, fixed-
focus jeweler's loupe (engraver's
glass). It has a focal length of approx-
imately 3 inches and objects a foot away
from the observer's position are focused
sharply.
After selecting the optical system,
mount it in a hole cut into the bottom
of the cup. A jeweler's saw or coping
I saw is ideal for cutting the hole. A
few drops of household cement will
hold the loupe in place. Paint the in-
side of the CUD with a jet black paint
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phone black. This will prevent stray
reflections.
Place an infra-red filter between the
tube and lens to reduce the effects of
stray illumination on the tube. No light
should be allowed to enter the unit ex-
cept through the lens. The light source
must of course be filtered if it is to be
invisible. Near infra-red filters will cut
out most of the visible light. Far infra-
red filters, while of somewhat lower
efficiency, will cancel out visible light
completely. They must be used with
comparatively powerful light source.
Infra-red filters can be purchased
from a number of scientific and pho-
tographic supply houses. Experimental
infra-red filters can be made by sand-
wiching several layers of red and blue
cellophane between two sheets of clear
plastic.
The image-converter tube is inserted
with the metal end toward the mouth
of the cup. The thin flexible lead con-
nects to the positive side of the power
supply. The other end of the tube has
a ring of graphite around the outside.
This is the cathode terminal. This
makes contact with the B-minus lead
through a strip of spring brass or a
thin coil spring formed to fit snugly
around the cathode terminal. A piece
of rubber tubing holds the tube in
place. It is protected by a window cut
from clear plastic and held in place
with three brass clips as shown in
the photograph.
The handle is a plastic bicycle han-
dlebar grip cemented over a hole drilled
in the side of the drinking cup for the
high-voltage leads.
The light source
The required intensity of the light
source is determined by the distance
from the target to the lens. Heat lamps,
flashlights, and ordinary bulbs will
work well for most indoor applications.
Our model is equipped with automobile
parking light housings on both sides.
These supply a limited amount of illu-
mination. The intensity of the parking
lights is insufficient for many applica-
tions and a heat lamp is used. Outdoor
applications involving greater distances
require a bulb with a sharply focused
reflector. The sniperscope used a 30-
watt, 6-volt bulb operated on a small
rechargeable storage battery. Good sub-
stitutes are auto headlamps, the sealed-
beam type being preferable for this
purpose. The heat lamps mentioned are
of course those sold for infra-red
treatment.
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.1. 1.1 .1 I
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WINDOW GRAPHITE CATHODE TERMINAL
PLASTIC CUP
ENGRAVER'S GLASS
PLEXIGLAS
EYE
4
MAGNIFYING
LENS
(OPTIONAL)
PLATE
TERMINAL
INFRA-RED CONVERTER TUBE
INFRA-RED
FILTER
HANDLE
TO POWER SUPPLY 3.5-60
Fig. 2?The construction of the snooperscope.
Snooperscope experiments
A number of interesting and enter-
taining stunts can be devised around
the snooperscope's ability to look
through any opaque material which
passes infra-red rays. Crime-detection
laboratories use parallel equipment for
reading through certain types of ma-
terial. Since the infra-red reflection of
pigments in paints and inks is different
for white light, it is possible to detect
forged paintings and checks by the way
the colors appear. Demonstrate this by
writing a message with India ink and
then painting it over with a coat of or-
dinary fountain-pen ink. The eye will
only see the blackened spot but the
snooperscope will peer through the top
layer of ink and reveal the writing
just as clearly as if there were no top
coating. This type of inspection can be
made photographically if infra-red film
is used in a camera. The electronic
method permits instantaneous exami-
nation, which is often a great con-
venience as well as an interesting ex-
periment.
Driving in fog has always been a
great hazard. An infra-red beam will
display the road with 30% more clarity.
This increase may be the difference be-
tween a safe situation and a very dan-
gerous one. Snooperscopes for this pur-
pose require very good lenses and pow-
erful headlights. It would probably be
difficult for an experimenter to con-
struct one and dangerous to use it.
The image-converter tube can be used
as an infra-red phototube. Reduce the
voltage to 250 or 300, and insert a
470,000-ohm to 1-megohm resistor in
the B-plus lead. Connect a two-tube
amplifier and relay across this resistor.
The relay operates when infra-red rays
strike the converter tube, changing the
voltage across the resistors.
A modified snooperscope has been
used in bioloeical laboratories to study
the behavior of rats and other small
nocturnal animals in total darkness.
The converter tube has been used with
a microscope to study bacteriological
and botanical specimens under infra-red
rays. They have also been used in
measuring temperatures of materials
below visible red heat.
For additional reading on this sub-
ject, see:
Forsythe, William E., Fluorescent
and Other Gaseous Discharge Lamps.
Pratt, T. H., Journal of Scientific
Instruments, Vol. 24, No. 12, December,
1947.
Monahan, A. C., Science News Let-
ter, Vol. 50, page 26-28, July 13, 1946.
Pratt, T. H., Electronic Engineering
(London), Vol. 20, No. 247, page 278,
September, 1948; and Vol. 20, No. 248,
page 314, October, 1948.
SNOOPERSCOPE TUBE
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The Infra-Red
Image Converter Tube
Based on a Lecture delivered before the Electronics Group of The Institute of Physics
Pr HE principle of the infra-red
image converter tube is not
new but it has only been with the
development of equipment for
Service applications that any parti-
cular interest has been shown in
such devices. In principle the
image converter is a system for
rendering visible radiation of wave-
lengths lying outside the range of
spectral sensitivity of the human
eye. Several tubes have been
described in the scientific journals,
and the wartime work has consisted
of the development of operationally
serviceable equipment based on the
principles given in the published
accounts. In particular, equip-
ment has been produced for Service
use that transforms an image in
the near infra-red spectral region
into an image visible to the eye.
It is, perhaps, appropriate first
to make a brief reference to this
near infra-red region of the electro-
magnetic spectrum which lies
between about 8,000 and 13,000
Angstroms (0.8 and 1.3 microns).
The lower wavelength represents the
approximate long wave limit of the
response of the eye,' while the upper
figure is the long-wave limit of sensi-
tivity of most of the photodetectors
available for use in this region.
Transmission of near infra-red
radiation through the atmosphere
is virtually the same as that of
visible light. In particular it should
be noted that at wavelengths so
slightly removed from the visible,
no useful advantage is obtained in
conditions of mist or fog. The
tungsten filament lamp running at
normal colour temperatures (say
2,800? K.) is, of course, an extremely
efficient source of radiation in the
region of one micron, and was used
in all Service applications.
By T. H. PRATT*
The main phenomena used for
detection in the region are photo-
graphy, photoconductivity, phos-
phorescence and photoemission. In
the case of the first of these, the
sensitivity of the photographic plate
can be extended to about 1.3
microns by the use of a suitable
dyestuff such as pentacarbocyanine
to absorb radiation and transfer the
energy to the main silver bromide
lattice. Results obtained in long
range aerial photography using
infra-red plates have led to the
widespread impression that near
infra-red radiation will penetrate
mist, but it must be stressed that
the increased atmospheric penetra-
tion is only obtained through the
small particle haze that is present
even under conditions of the best
visibility. Photoconductivity and
phosphorescence rely, as does the
photographic plate, on an internal
photoelectric effect. In the former,
absorption of radiation raises elec-
trons to the conduction level from
impurity centres in a semi-conduc-
tor lattice, with a corresponding
variation in resistance, while in the
case of phosphorescence, electrons
that have been raised into trapping
centres by some activation process,
are removed from these centres by
the infra-red radiation and return
to the ground level with the emis-
sion of visible radiation. The best
known photo-conductor in this
region is thallium sulphide,' while
typical of an infra-red sensitive
phosphor is strontium sulphide
sensitised with samarium and euro-
pium.' In the case of photo-
emission, we have the external
photo-effect, the absorption of radia-
tion completely removing electrons
from a layer. The main infra-red
sensitive layer consists of a silver
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rI00
3
cc
oci
0
80
m 40
5
INFRA-RED
FILTER
Fig. I. The near
infra-red region of
the spectrum
Cs.- 0-Ag.
PHOTO-SURFACE
I- R
WAVELENGTH
caesium oxide compound surface.'
It is, of course, this latter effect
that is used in the infra-red image
converter tube. Image converter
tubes relying on an internal photo-
electric effect and an electron mirror
system' will not be considered here,
nor will devices such as the image
orthicon in which the visible image
is not formed in the tube itself.
Principle of the Image Converter Tube
In the infra-red image converter
tube, an image formed with radia-
tion of about 1 micron wavelength
is transformed in to a visible image.
.The infra-red image is focused on
to a Ag-O-Cs photo-cathode and the
electrons emitted caused to impinge
on an anode in the form of a
fluorescent screen. The converter
may thus be divided into three
main components, the photo-
emissive surface, the electron
optical system, and -the screen, with
each of which it is intended to deal
briefly here.
The photo-emissive effect in an
Ag-O-Cs layer results from the
removal of electrons from the outer-
most orbits of the caesium atoms
by absorption of infra-red radia-
tion. The energy transferred to an
electron by a photon is sufficient
not only to enable it to leave the
field of influence of the parent atom
but also, under favourable condi-
tions, to overcome the forces of sur-
face attraction and so leave the
layer and pass into the evacuated
space outside. The magnitude of
the effect is dependent upon the
wavelength of the incident radia-
tion, and in the case of the corn-
MICRONS
posite caesium surface, peak
response occurs at about 8,000
Angstroms with a long wave cut-off
at 13,000 Angstroms. The number
of photo-electrons is proportional to
the intensity of radiation, although
at room temperature there is always
a number of electrons leaving the
surface as a result of thermal
agitation. There is some spread
in velocity among the photo-
electrons corresponding to the
different wavelengths (energy) of
the exciting radiation and to the
varying depths in the layer at
which the electrons are released.
< The high accelerating voltages
employed render this spread of velo-
city unimportant. Since the number
of electrons leaving a point of the
photo-sensitive surface will be pro-
portional to the intensity of radia-
tion at that point (ignoring the
background of thermal electrons), it
can be seen that the electron
density immediately outside the
surface will vary from point to
point according to the correspond-
ing variation in the intensity of the
infra-red image focused onto the
surface. The infra-red. image has
thus been replaced by an electron
image.
The electrons forming this image
are accelerated towards the fluores-
cent screen anode by an applied
field of several thousand volts, and,
except in the simplest forms of
image converter, pass through
some form of electron optical system
in the process. The high voltage
both limits the electron spread
during the passage from cathode to
anode and also gives a fluorescent
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Fig. 3. Types of infra-red image converter
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Fig.2. Prin-
ciple of the
image con-
vertertube
INFRA -RED
RADIATION
FROM OBJECT
SEMI-TRANSPARENT ELECTRON FLUORESCENT
PHOTO CA ODE PATHS SCREEN ANODE
OBJECTIVE
LENS
INFRA-RED
IMAGE
image of high brightness. The ten-
dency of electrons to follow helical
paths about magnetic lines of force
may be utilised to bring all the
electrons leaving a point of the
cathode to a. point focus on the
screen irrespective of the original
angle of emission of the electrons.
Alternatively an electrostatic focus-
ing system may be employed when
the inverted infra-red image formed
by a normal glass lens on the photo-
cathode may be reproduced as an
erect . image on the screen, and
further the size of the latter image
may to some extent be varied. It
is an advantage to reduce the size -
of the fluorescent image and so, by
increasing the electron concentra-
tion, obtain a brighter image on the
screen. An electron optical reduc-
tion to about one-half is the
optimum. The principles of elec-
tron optics and the analogy to
normal . optics are well known,
applications being widespread in
both the field of electronics and, for
example, electron microscopy. Use
is made of the fact that electrons
are deflected by an electrostatic
field, tending to follow a path at
right angles to the equipotential
lines. Thus the electron lens formed
by the field between two adjacent
co-axial cylinders of different poten-
tial has a similar focusing effect on
a parallel bead of electrons as does
a convex glass lens on a parallel
beam of light. In the image con-
verter tubes use is made, for the
most part, of either cylindrical or
aperture electrostatic lenses. Little
use has been made of electro-
magnetic lenses owing to the greater
weight of such systems.
After passing through the elec-
tron optical system the electrons
impinge on the fluorescent screen.
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ELECTRON
OPTICAL
SYSTEM
VISIBLE
IMAGE
Various compounds are available
for use as screen material, for
example, zinc sulphide and wille-
mite (zinc orthosilicate). The com-
parative inertness of the latter to
caesium contamination makes it
particularly suitable, as does the
colour (green) which corresponds
roughly to the maximum sensitivity
of the eye. Bombardment by high
velocity electrons will, of course, cause
the Screen to glow. The intensity of
the light emitted by the fluores5ent
material is proportional to the
number of electrons striking it,
and thus the variations in bright-
ness from point to point of the
fluorescent image will correspond
to the variations in electron density
in the electron image which, in
turn, is directly related to the
variations in intensity of the original
infra-red-image. The latter has
thus been transformed into an
image visible to the eye.
Historical Development
The development of the image
converter tube may be traced back
to. the modification of the electron
microscope employed, for example,
by BriicheT in an investigation of
metallic surfaces. The state of a
surface is, to some extent, reflected
in the electron emission under
ultra-violet . irradiation. Briiche
formed an image of a zinc surface
in an plectron microscope using the
electrons emitted by the zinc when
illuminated with a mercury arc.
Other workers used similar systems
and it was a logical development to
arrive at a device in which the elec-
trons imaged on the fluorescent
screen originated from an infra-red
image focussed on a caesium photo-
surface. In 1934 the first descrip-
tion was published of a normal
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of which had earlier been advanced
in the form of a patent (B.P.
326200) by Hoist, and his co-workers'
of Messrs. Philips of Eindhoven.
Their arrangement is of particular
interest since it was chosen by the
Admiralty in 1940 as the basis of
the British Service image converter
tube. The cylindrical glass envelope
of the tube is fitted with two plane
parallel windows, on one of which
is deposited the photo-cathode, on
the other the fluorescent screen. An
accelerating potential of a few
thousand volts is applied between
anode and cathode which are
separated by a distance of 2 cm.
The photo-electrons emitted are
accelerated along a straight path
by the homogeneous electrostatic
field and impinge on the fluorescent
screen giving rise to a visible image
bearing a one-to-one correspondence
to the original infra-red image
falling on the cathode. The defini-
tion attainable with such a simple
device is limited by the varying
angles of emission of -the photo-
electrons and by the spread due to
mutual repulsion during passage
to the screen. Coeterier and Teves
later introduced improvements to
the simple system, and experi-
mented with alternative focusing
devices.
Also in 1934, Farnsworth pub-
lished in America details of a so-
called image dissector tube for
television purposes.' In his tube a
plane cathode was used with a
uniform electrostatic field, together
with a uniform magnetic field pro-
duced by a solenoid wound around
the outside of the tube. Since
electrons travel in helical paths
about the magnetic lines of force,
all electrons leaving a point of the
cathode, whether in a normal direc-
tion or not, can be brought to a
point focus in the final image plane
by means of the magnetic field. It
can be shown that the position of
this focus is independent of the
transverse velocity of the electrons
on emission. In the image dis-
sector tube, the whole electron
image was deflected by means of
additional magnetic coils, so that it
fell point by point on the collecting
anode after passing through an
0.015 in. aperture. This aperture
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using a 4 in. cathode Farnsworth
achieved a 210 line picture.
Although developed as the basis of
a television camera, in which appli-
cation an electron multiplier was
added to the anode, in order to
examine the quality of the electron
image the collecting anode may lw
replaced by a fluorescent screen,
when the system corresponds to
that of Hoist with the addition
of a long magnetic lens.
The focusing effect of the long
magnetic lens and the consequent
improvement of definition led
Coeterier and Teves to modify the
Philips tube to include a uniform
magnetic field." They also con-
structed tubes in which use as
made of a converging field that
permitted an electron optical reduc-
tion in image size. The in,preve-
ment in definition resulting from the
employment of focusing s.% stems
was calculated by Henneherg nul
Recknagel of A.E.G." Three
systems were considered,. the
uniform electrostatic field, the
electrostatic field with uniform
magnetic field added, and a short
lens. Calculated circles of confusion
in the three cases were:
2IE 2L V
41,s1 ? ? --- ?
L ? L' (2V + 1) '
where 1 is the anode-cathode
spacing, E, the velocity of emission
of the photo-electrons, and U, the
final velocity of the electrons. In
the third formula V is the magni-
fication, and L the cathode-lens
centre spacing. With a factor E I'
of the order of 10-4 a resolution .of
250 lines per in. (black plus white)
might be expected from the simple
electrostatic arrangement with a
gain of about 100 times with the
magnetic field. In practice E.M.I.,
Ltd., achieved a better figure and
Coeterier and Teves with the long
magnetic lens reported a resolving
power many times better than with
the simple system. In general, the
theoretical gains with lens systems
have not been obtained.
Tubes employing more complex
electron optical arrangements were
soon investigated. Pohl" first
described the use of a short
lens between cathode and anode.
Heimann" of the German Post Office
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Fig. 4. Early
R.C.A. tube with
electostatic fo-
cusing.
Laboratory developed a tube
employing both magnetic and elec-
trostatic focusing, the latter being
carried out by two metal cylinders
at different potentials. The electro-
static lens inverted and reversed the
fluorescent image relative to the
infra-red image on the photo-
cathode so that the orientation of
the final image correspon& to that
of the object. Schaffernicht" also
produced a tube with combined
electrostatic and magnetic lenses
resulting in an electron optical
reduction in image size, whereas
Heimann's tube gave a magnified
fluorescent image. The opaque
cathode was deposited on a con-
cave surface and the shape on the
anode cylinder was such that a suit-
able focusing effect was produced
with a single applied voltage. Move-
ment of the magnetic lens enabled
the magnification to be varied.
Cathode-anode spacing was 40 cm.
and accelerating potentials up to
20,000 volts were applied. The
original tube was not, in fact, an
infra-red image converter, but
employed an ultra-violet sensitive
potassiu,m photo - surface. Von
Ardenne" describes a similar
arrangement in which the cylindrical
electrostatic lens incorporated a
resistance element in the form of a
fine nickel spiral. It was claimed
that the system resulted in reduced
field emission owing to the lower
potential gradient in the vicinity of
the cathode.
Early RCA Tubes
' In America, Zworykin and
Morton," of R.C.A., reported on
optical systems for image converter
tubes using only electrostatic focus-
ing. A curved cathode was used in
conjunction with a series of focusing
rings giving a compromise between
the resistance lens and the single
element (Fig. 4). Introduction of an
aperture between lens system and
anode enabled the magnification to
be varied-. Morton and Ramberg"
extended the investigations of this
type of system using moveable
anode and cathode. The R.C.A.
team also described a tube employ-
ing a uniform electrostatic field and
a long magnetic lens."
Continuing their work on image
converters, Coeterier and Teves"
developed a tube that could be used
conveniently with an opaque photo-
cathode and fluorescent screen. Use
was made of a magnetic field to
deflect the electrons through a
right-angle. The radiation passed
through the wall of a spherical glass
bulb before falling on the cathode
on the back wall of the bulb. The
anode was mounted in the neck of
the bulb at right angles to the
cathode, both anode and cathode
having a cylindrical magnet behind
then'. An accelerating potential
up to 10,000 volts was applied. An
alternative arrangement was also
used in which the positions of anode
and cathode were reversed and a
third electrode ?added in the form
of a ring spaced a short distance
from the cathode. The accelerat-
ing voltage was applied between
ring and cathode so that the deflect-
ing and focusing action took place
in a region free from any disturb-
ing electrostatic field. A further
development consisted of a double
system in which the first anode con-
sisted Of a caesium treated plate,
the secondary electrons from which
were in turn focused mi a fluorescent
screen.
In 1938, E.11LI., Ltd., produced a
system employing a plane parallel
cathode and anode with a long mag-
netic lens, either in the form of a
solenoid or a permanent magnet.
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I I I 11111 1111 II LLIJL-111.1-1-1 1111,,...ILLL J11111-1.. L-11, 1, ILLll Ail
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oasea on me original noist aesign.
When the complexity of the Super-
Emitron television camera is com-
pared with the simplicity of the
image converter, it is perhaps not
surprising that within a month or
two Dr. J. D. McGee, of E.M.I.,
was able to demonstrate a success-
ful tube of the simple type.
gl Mb were III LW-
duced between cathode and anode.
This resulted in a substantial
improvement in sensitivity at the
expense of resolution. It thus came
about that, at the outbreak of war,
some ,form of image converter tube
was available in this country, in
-America, in Holland, and in
Germany.
Fig. S. Comparison of definition of
War-Time Development
Consideration of the military
applications of infra-red image con-
verter tubes was commenced by the
Admiralty in 1938. It soon became
apparent that the devices already
available were too cumbersome for
many of the possible Service uses,
although technically the perfor-
mance was promising. In addition,
production techniques were diffi-
cult. After comparative tests of
the available British, American and
Dutch gear in 1940, it was decided
that if useful quantities of equip-
ment were to be available for
Service use in an acceptable time,
the l original system of Hoist offered
the best possibilities. The -Philips
team had given a number of reasons
why the simple arrangement was
undesirable?for example, the ,diffi-
culty of working at high voltages
with a small cathode-anode spacing,
- optical retroaction between fluores-
cent anode and the cathode, and the
relatively low sensitivity of semi-
transparent photo-surfaces, but it
was considered that simplicity justi-
fied a fuller investigation. Accord-
ingly E.M.I. were asked to under-
(left) and (right) A.E.G. tubes
E.M.I. Tube
The final arrangement of the tube
is shown- in the photograph of?Fig.
3. The cylindrical Pyrex envelope,
5 cm. in diameter and 4 cm. in
length, is fitted with plane end
windows 2 mm. in thickness. On
the inside surface of one of these is
deposited the semi - transparent
Ag-O-Cs layer, while the screen is
mounted at a distance of 5 mm.
from the photo-surface. The wile-
mite is .deposited on a thin glass
disk on which a platinum graticule
has been sputtered to reduce screen
resistance. The screen mounting is
carried on tungsten wire supports
sealed into the second window
through which the fluorescent image
is viewed. Cathode contact is made
by a platinum paste seal at the edge
of the window. To prevent caesium
contamination of the willemite and
to facilitate the deposition of -a
uniform photo-surface, during the
activation processes the screen lies
with willemite surface downwards
on the back window of the tube.
Evaporation of both silver and
caesium is carried out by electrical
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the tube itself. Otherwise the pro-
cesses employed are similar to those
normally used in the preparation
of this type of layer. Care in design
and manufacture resulted in a high
level of insulation being maintained
and potentials of between 3,000 and
7,000 volts can be applied to the
tube without failure. The deposi-
tion of the cathode on a plane glass
surface without any associated
metal parts helps in this respect by
reducing cold emission. The final
sensitivity of the semi-transparent
photo-cathodes was comparable with
the values normally obtained for
opaque surfaces of the same
material.
Declassified in Part -
RCA Tube
Both the American and German
tubes developed for military appli-
cations employed electrostatic
focusing. The R.C.A. tube has
been described by Morton and
Flory. Use is made of a four-
component cylindrical lens in con-
junction with a curved cathode, the
actual curvature of the latter be;ng
a compromise between light end
electron optical considerations. The
introduction of low potential com-
ponents between cathode and main
lens enables a sufficiently flat image
plane to be obtained. The electron
optical magnification is 4, which
represents the best compromise
between the brightness of the
fluorescent image and the power
and exit pupil of the viewing. lens
required. Accelerating potential is
4,000-3,000 volts. The overall dimen-
sion i of the tube are 11 cm. length
and 4 cm. diameter.
AEG Tube
The production version of the
A.E:G. tube manufactured for the
German forces Used an aperture
lens requiring a single intermediate
potential. Again image distortion
was reduced by using a curved
cathode and electron optical magni-
fication was about 4. A high.volt-
age was applied to the tube (up to
17,000 volts) and the image bright-
ness was further enhanced by the
application of an aluminium layer
to the back of the screen. Overall
dimensions were 8 cm. by 16 cm.,
although a smaller version was com-
mencing production at the end of the
war; The photographs of Fig. 3 show
the development of the various tubes
. !vents and the relative sizes can be
, judged from the scales. The simplicity
of the British tube resulted in it
being the first to become available
in production quantities, whereas in
the case of the A.E.G. tube, in spite
of very much greater development
effort, Service equipment had only
reached the training stage in? the
German army at the end of the war.
Although the E.M.I. tube repre-
sents the best compromise between
.performance and complexity in the
applications for which it was
originally intended, namely the
detection of sources such as infra-
red homing beacons, the more com-
plex focusing systems are an advan-
tage where extended images are
involved. Some gain in resolving i
power s possible, using a lens
system, but operationally the more
important advantage, is the higher
brightness level of the fluorescent
image. The electron optical reduc-
tion combined with a high power
viewing lens is partly responsible
for this gain. In addition, thy
larger cathode-anode separation en-
ables higher accelerating voltages to
be used as in the case of the
A.E.G. tithe. Comparative resolving
powers of the British and German
tubes are shown in Fig. 3. The
uniform resolution over the whole
screen of the former is apparent as
is the high resolution at the
centre of the screen in the case of
the latter. Exposure time in photo-
graphing the screen of the British
,tube was several times that p.111161.4
for the A.E.G. tube.
References
e. F., Prw.B.8., 155A. 664. 1936.
Brooker. L. 0. S.. and Keyes, G. H.. ./. Frank.
mat.. 219. 255, 1935.
Case, T. W., Phr. Pee., 111, 269. 1920.
1-rhaeh, F.. Pearlman. D.. Hemmenglinger. H.,
./.0.S.A.. 36. 372. 1946.
' Campbell. N. K.. Phil. Mew.. 6. 633. 192A.
? Hottenroth. G.. Ann. d. Phy,,.. 3o, 669. 1937.
Bruehe. E.. Z. f. Phys.. $6. 446. 1933.? ?
Hoist, 0., de Boer. J. H.. Teves, M.C.. and
Veenemans. C. F.. PhyAfra. 1.297. 1934.
? Farnsworth. P. Fronk. mat.. 21,4. 411. 1934.
Coeterier. F.. and Teves. M. I.. Phy.iro. 3, 964,
1936.
" Fienneberg, IV.. and Reeknagel. A.. Z. f. tech.
Phe., 16. 230. 1935.
12 Brodie. S.Kerzcr,
Spring.-r. 'krill), 1934.
" Heimann.' W., EST. 12. 494. 1936.
14 Schallernicht, W.. Z. f. Phgx.. 93, 762. 1935.
" on Ardenne. M.. EST. 13. 230. 1936.
" Zworykin. V. K.. and Morton, G. A.. ./.0.s.?4.,
26. 161, 1936. -
1' Morton, G. A., and Ramberg, E.41.. Phfpgies, 745,
1936.
" lams., H? Morton. 0. A., and Zworykin. V. K..
Priv. I.B.E., 27. 541, 1939.
Coeterier. F., and TeVe4..M. 4.. PhyAirn. 4, 33.1.07
'? Morton. 0. A.. and Flory, L. E.. Elertroni,.. 19
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ilL 11E11- I 1
I II I
The Infra-Red Image
Converter Tube
By
T. H. PRATT
Infra-Red driving equipment mounted on a jeep
Service Equipment
ATYPICAL complete Naval re-
ceiver of the type used for beacon
detection is shown in the diagram. of
Fig. 6. ,An aspheric plastic objective
lens, used in conjunction with a
plastic field, flattening component
focuses infra-red radiation from a
distant beacon on to the photo-
cathode. An infra-red filter is
included in the optical system. to
reduce the effect of .stray illumina-
tion such as moonlight. The field
of view is 25?. The screen is viewed
through a simple piano-convex eye
lens set at a fixed focus of 1
dioptre. Presentation is, of course,
inverted and reversed.
In all applications it is necessary
to have a source of infra-red radia-
tion, and in this respect the high
i
efficiency n the one micron region
of the tungsten filament lamp run-
ning at normal colour temperature
is convenient. The lamp must be
screened with some material that
absorbs visible light while transmit-
ting infra-red radiation. Several
filters were developed by the
Admiralty and produced by firms
such as Erinoids and B.I.P. Most
filters consisted of a plastic base in
which was incorporated a dyestuff
with the required transmission
characteristics. Polyvinyl alcohol,
melamine, viscose and cellulose
acetate are typical bases, while a
polyazo direct dye such as naptha-
lene leather carbon is a suitable
dye. Typical transmission charac-
teristics given in terms of Kodak ,
Wratten 87 are:
Infra-red
Transmission
Visual (to a Ag-O-Cs
Transmission ! photosurface)
25%0 75%
2% I 50%
? 20%
Reprinted from
Electronic Engineering
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In most apPlications the trans-
mission of some visible red light
through the filter was permissible
particularly in view Of the low sensi-
tivity of the retina (except for the
fovea) to red light. Data has been
published on similar infra-red filters
developed in America.'" Where
high power transmitters were con-
cerned and plastic-based filters un-
suitable, use was made of a Chance-
Pilkington pigmented glass.
In applications involving the view-
ing of any extended scene an erect
presentation is obtained by the
introduction of an erecting viewing
system as shown in Fig. 7. This
instrument, which is .a binocular,
employs as objective a 11 in. focal
length 1/1.9 projection lens, a
cemented doublet erector and a 1 in.
Ramsden eyepiece. A resolving
power of 350 lines per in. on the
cathode is obtained at one foot-
candle level of target illumination,
at whieli level the visual acuity of
the eye is the limitation. In the
case of these picture-forming appli-
cations where the best resolution
and brightest image are required, a
voltage of about 6,500 volts is
applied to the tube from a vibrator
power unit. The weight of the
receiver is about 7 lb. and the
dimensions 16 in. by 6-1 in. by 5 in.,
the power unit with cold cathode
rectifier weighing about 5 lb. and
being S in. by 51 in. by 3 in. in size.
It is interesting to compare the
weights of the various British
receivers with the equivalent Ger-
man instrument, which weighed
27 lb. and was 21 in. long and 6 in.
diameter, with a power unit of
weight, 20 lb. and size 11 in. by
84 in. by 7 in. The relative sizes of
the tubes themselves are shown in
Fig. 8.
Service Applications
Service applications of image con-
verter tubes fall into two distinct
categories. The first is concerned
with the detection of distant sources
of infra-red radiation such as hom-
ing beacons, the second with the
observation of a scene illuminated
TUBE
ELECTRONS
PLASTIC LENSES
SIMPLE
EYE LENS
ZAMBONI
PILES
(1600 VOLTS
EACH)
0 -
2 -
GLASS PLATE
INVISIBLE
INFRA?RED
RAYS
DYED PERSPEX I.R. FILTER
RASS END CAPS
SPRPNG
PAPER ELEMENTS
EXONITE TUBE
TIGHT PERSPEX CASE
BALL BEARING GRAVITY SWITCH
3 ?
INCHES
'AN
? ?,???,??,??????
Fig. 6 Infra?red
receiver with enclosed
Zamboni pile power unit
for beacon detection
with infra-red radiation. The
earliest operational uses were of
equipment of the first type in con-
nection with special Naval opera-
tions in the Mediterranean in 1041.
The Naval applications were almost
all concerned with homing aids.
Thus, in all the X-craft operations,
commencing with the attack on the
Tirpitz in Alte Fjord and continu-
ing with the operations in the Far
East, the craft returned to parent
vessels using an infra-red telescope
to home on an infra-red beacon.
Again, the small combined opera-
tions pre-invasion reconnaissance
parties that worked along the coast
of France and North Africa and
later in Malaya, used similar equip-
ment to enable canoe parties to
return to parent craft. Infra-red
beacons or corner cube reflec-
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I I I ? 1 Ill I
MULCT
ILLLINONATID
Or
INTRA-RCP
LIGHT
OGJECTISIC
LEN
IRONY 515005 fLOONESCOO
or TUNE %RUN
INSTRON
And.
LING
?000
cam=
CONTACT
RING
ELI
STREAM
MOM
CONTACT
RING
h..
LI o
Fig. 7. Infra?red receiver for viewing
tors served to mark beach ren-
dezvous for the collection of person-
nel operating inside enemy territory.
R.A.F. applications were con-
cerned with recognition systems. In
1942, when German intruder air-
craft were mixing with our return-
ing night bombers, night fighters
were equipped with an infra-red
receiver and a coded infra-red
beacon was attached to the tails of
our bombers. Before carrying cut
an attack, the fighter pilot glanced
in his telescope and if the plane
ahead was British the appropriate
signal would be seen. Later in
1944, a similar device was fitted to
rear turrets of night bombers to
enable rear gunners to dift,m-entiate
between members of the bomber
stream and German night fighters,
the former being fitted -witn suit-
able beacons shining forward.
The main Army application was a
night vehicle driving aid, using
normal headlamps covered with
infra-red filters in conjunction with
the binocular receiver for viewing
the terrain ahead. This arrange-
ment enabled convoys of armoured
or supply vehicles to move at night
over roads or open country at speeds
about equal to normal daytime
convoy speeds without danger from
air observation. The eqi,ipment
was fitted as a navigational aid on
amphibious vehicles used in ferry-
ing 'troops across the Rhine dui ing
the main crossing. The Army also
possessed quantities of simple
KT.
GLAND
TING
LENS
CE
LOTS NEATEN
SINGING
illuminated with infra-red radiation
receivers for use as countermeasures
in the event of enemy use of infra-
red.
Research and Commercial
Applications
The first image converter tubes
were not, of course, developed with
a view to military applications. As
has already been stated, Brche
was concerned with the examination
of the surface of a metal plate using
the electrons emitted under ultra-
violet illumination to form a fluores-
cent image of the surface. Similarly
Kluge used the form ef tube
developed by Heimann for an
investigation of semi-transparent
photo - surfaces. The application
to spectroscopy" is immediately
apparent since the tube can Ise used
for the direct observation of emis-
sion or absorption phenomena out to
1.3 microns. During the ?A ar an
image converter tube attachment
was made for the N.P.L. spectro-
meter to facilitate the direct
measurement at one TA icron of
the refractive indices of various
Inaterials used in the optical com-
ponents of infra-red receivers. The
R.C.A. workers described the use
of their tube in conjunction with a
microscope for the observation of
biological and botanical specimens
in the infra-red.'
Useful information can be
obtained on animal behaviour in the
dark using infra-red viewing equip-
ment. During the war this was
applied in connection with an
investigation on the sensitisation of
the retina to infra-red radiation.
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R.C.A.
0 I ?
11111[111
INCHES
More recently Colonial Office field
team's have used instruments for
obseiving rats in the dark in the
course of an investigation of the
spreading of scrub typhus in the Far
East, and for observing the
behaviour of malaria-carrying mos-
quitoes in the dark over water.
Although the wavelengths to which
the image converter tubes are sensi-
tive are too short to be preferen-
tially .transmitted through natural
scattering media such as fog, where
? scattering particles are sufficiently
. small, some advantage can be gainef
by using an infra-red receiver. Thus
descriptions have been given'" of the
applieation of the converter tubes to
ophthalmic problems connected with
certain types of corneal opacity.
Infra-red aids have immediate
application to the production of
photographic materials. Simple
manipulative work, time studies
and inspection are all made in-
estimably easier using the simplest
devices. The use of optical pyro-
metric methods at temperatures
below visible red heat is made
possible by the use of the image
converter tube. Many of these
applications are only now being
investigated fully, but there is no
doubt that the. return from the war-
time effort will be considerable in
the fields of research and industry.
References
E.g. Elementary Lessons in Electricity and
Magnetism, Silvanus Thompson. p. 180.
" Mout. E. R., Amon. W. F. Shepherd, R. (1.,
Thomas, A., West, ('. 1).. and Land, E. H.,
./.0.S.A., 36, 460, 1946.
" Shenk. J. R.. Hodge. E. S.. Morris. R. J.. Pickett,
E. E., and Brode, W. R.. J.O.S.A., 36,569,1946.
" Eluge. W., Z.! Phys., 93, 789, 1935.
Schaffernicht, W.. Z. f. tech. Phys., 17, 596, 1936.
Vasko. and Peleska, Ophth. July 1947.
2' Kelly, T. S-B, B. J. Ophlh., July 1948. ?
A.E.G.
Fig. 8 Relative
sizes of British,American
and German tubes.
T4 '..*...-'..."'.'....r' "''.......01."...... 0,0???......
ARMY PLANS TO BUY
6,918 `SNIPERSCOPES'
WASHINGTON, ?The
"night eyes" of the rifleman, the
.1' electronic "sniperscope" that is
credited with causing 30 per cent
, of all enemy casualties in the Oki-
nawa campaign, is being made a
/ standard item of Army equipment.
t Army sources disclosed today
! that !the field forces were so im-
pressed with the efficacy of the
auxiliary weapon that enables the
r infantryman to "see" the enemy
jthrough darkness that units in all
the krmy's ten divisions would be
equipped with the device.
Included in the Army's budget
requests now before Congress is an
1
$8,654,418 item for the purchase of
4 6,918 "sniperscopes" at a cost of
$1,251 each. How many of the / de-
Vir..e7- are already in use is con-
siuered secret information.
The "sniperscope" consists of an
electronic telescope that is mount-
ed on the standard Army .30-cali-
bre carbine. Wiring runs from a
portable power pack carried in a
t harnessed knapsack on the soldier's
back.
Operating under cover of dark-
ness, the rifleman points the
"sniperscope" and his gun sights
toward. a spot whence a sound has
come. By switching on an infra-
red spotlight, he makes rays scan
the territory. These are reflected
from the target, picked up by the
telescope and transformed into an
? image across the sights of the rifle-
man.
.141"..4?41100.6
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I IhoWIVIUNAIN I
SNOOPERSCOPE SUPPLIES
We have a limited quantity of the following
supplies for the construction of snooperscope out-
fits. All material is in new condition and carries our
- warranty to be free of defects in material or work-
manship.
SNOOPERSCOPE TUBE
SUPPLY LIMITED?
These are government
released British
snooperseope tubes
which employ the spe-
cial simplified design,
making construction of
experimental models
possible with simple
hand tools. Highly sen-
sitive, they provide a
SEE IN THE DARK bright clear image of
invisible infra red rays.
Also useful as infraared (invisible) photocells.
With complete hookup instructions. Special
Price $14.95.
SNOOPER5COPE BOOK
Shows in detail Army and Navy
snooperscopes, sniperscopes and infra
red telescopes. One of the few books of
its kind. Circuit hookups for practical
instruments are given.
Special Price $1.50.
NEAR INFRA RED FILTER?An efficient
filter that fits directly on the front of the
image converter tube. High quality glass
type with metal mounting clasp. Clasp
also serves as the graphite contactor
(?lead). Your Price 1.50
ENGRAVERS GLASS?Has a ground lens
for clear sharp images. Focal length three
inches. Perfect as either a front or rear
view lens. Plastic housing prevents elec-
tric shock. Price 1.25
IGNITION COIL?This miniature high volt.
age coil provides high output for snooper-
scope operation. Has built in condenser
for extra power. Special $2.2f
FILTERS?Infra red filter glass. Manufac-
tured by a famous glass house to exacting
specifications. Transmitts over 80% of
the infra red rays but appears as a total
black for visible light.
3 x 3 inch square Price $2.53
6 x 6 inch square Prise $4.00
PLASTIC FILTERS
Infra red plastic filters are also available at ISO each for small test square
and 75? each for 6 x 6 inch squares. Permits passage of heat rays but
appears black to visible light. Buy several at this price while the supply
lasts.
942 Kings Highway, Brooklyn 23, New York
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/MAJ. I IVPIAL
INFRA RED SNOOPERSCOPE SUPPLIES
The following -additional supplies were made available due to many
requests for materials with which to construct experimental infra red
instruments and snooperscopes. Sales of any item Is limited to stock
now On hand. New materials arriving daily.
POWER SUPPLY KIT?Provides the proper voltages for image converter
tubes. Operates off three ordinary flashlight cells. Completely portable
Every part including case, rectifier tube and batteries is supplied.
Your price $14.93
LENSES?These lenses are of top quality materials and intended for use
where the best possible results are required. We make these lenses
available only to our customers which have purchased our snooperscope
tubes and send us there written assurance that they have been success-
ful with the circuits and the simple lenses and now feel prepared to
construct the finer models.
SNOOPERSCOPE LENS ? Original Navy
Snooperscope lens. Schmidt optical system
type Government cost $134.00. Very fast
speed F 1.0 Our Price $12.50
Mounted Optical Lens. High quality
lens of fast speed. Excellent for
image tubes. Priced at a fraction of
their original cost. Price $8.50
HOW TO ORDER
IMPORTANT NOTICE
Sales are subject to the following conditions; all prices in this catalogue
is subject to change without notice. Most material is shipped postpaid unless
otherwise noted. Test instruments are not postpaid and postage fees should
be included with your order. We will insure all material unless instructed other
wise. In the event of damage in transit, write us immediately giving details o
f the damage and insurance numbers on package. If for any reason you wish
to return material write us first cjivina all detai's and we will send you ship
ping instructions. POSITIVELY NO MATERIAL ACCEPTED FOR RETURN UNTIL
WE HAVE BEEN NOTIFIED AND YOU HAVE OUR SHIPPING INSTRUCTIONS.
Merchandise made to customers own specifications cannot be returned. Foreign
orders should add 10% to cover costs of additional packing, postage and con
sular expenses. No C.O.D. orders accepted unless accompanied by a deposit of
25%, balance wil be shipped C.O.D.
This catalogue covers only a few of the items that we carry. We carry
hundreds of items not listed on these pages write us on your requirements.
Prompt efficient service is rendered on all orders regard'ess of size. Our lab
? oratory is engaged in the construction of scientific instruments of every de-
scription. We are always very happy to send our free quotations on equIpm
ent built to order.
PRECISE MEASUREMENTS COMPANY
942 Kings Highway, Brooklyn 23, New York
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1
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\otaall.1.1,111,/
Generates short ultraviolet
0111//////' radiation (1849A Se 2537A) which
produces ozone by converting
!"..?.. the oxygen of the air (02) into
ozone (03). Useful for fluores-
cent 8,7, phosphorescent ma-
terials. Uses only 4 watts of
power. Lamp supplied with
111 TV
socket and instructions.
Your Price $1.95
*freiyaranTrivr
BLACKLIGHT LAMP
Special Argon filled bulb pro-
vides a good source of violet and
ultraviolet light for blackout
experiments and fluorescent
materials. Very convenient as it
screws into any standard lamp
socket.
Clearance Price 45c
10 for $4.00
FLUORESCENT PIGMENTS
Brightest glowing, concentrated phosphors,
available in many colors. Red, White, Blue,
Green, Yellow and Orange. Mix with clear
lacquer for painting.
SAMPLE SIZE (specify color) 35c each
COMPLETE SAMPLE KIT (6 colors) $1.75 ea.
One Ounce Bottles (specify color) 50c each
AMAZING BLACK LIGHTS
Powerful 250 watt Ultra Violet
Bulb is very convenient to use
as it screws into any standard
lamp socket. Provides black light
which causes many things to glow.
Excellent for experimenting with
fluorescent and phosphorescent
pigments. Lamp is designed for
intermittent duty only.
Price $1,95
PHOSPHORESCENT PIGMENTS. Expose these pigments to sunlight or ultra
violet light or ordinary light bulbs. Pigments wil then remain glowing for
sometime afterward in total darkness. Comes in powder form mix with
clear lacquer for painting. Available in three colors: yellow-orange,
green and blue. One ounce bottle 600 1/2 pound bottle $2.75
SAMPLE KIT. Consists of one of each of the above coolrs (three bottles).
Price 98 cents.
SPECIAL PHOSPHORS
ULTRA VIOLET
Energize this phosphor with short wave ultra
violet light (approx. 2500 A) and it will convert
it to the near ultra violet of approx. 4000 A.
This phosphor when used with many types of
black lights will increase the ultra violet out-
put considerably. Use as a coating on the out-
side of photocells to change their response.
Sample 500 1 or. Bottle $1 $12.50 lb.
SHORT WAVE
Responds to wavelength of 2500 A or shorter.
Will detect alpha particles, electron beams, etc.
Lights up a bright green.
Sample 50? $12.50 lb. 1 oz. Bottle $1
TWO COLOR
The beautiful colors that these concentrated
phosphors will glow depend upon the wave-
length. Different types of blacklights will make
it change color. Red and green or yellow and
green are available.
Sample 500 $12.50 lb. 1 bz. Bottle $1
INFRA RED EMITTING
This unusual material has the property of emit-
ting far red and infra red radiation when ex-
cited with ultra violet light. Useful as infra red
light sources, experimental fluorescent lights,
etc. Price $4 oz.
INFRA RED RESPONSIVE
A specially prepared material with rare earth
activators. Charge with ultra violet light or
alpha particles, phosphor then stores this en-
ergy and releases it in the form of light when
infra red radiation is present. Also useful as
temperature indicators.
Price $4 oz
ULTRA VIOLET FILTERS
Glass type. Filters out most of the visible light
while allowing free passage of ultra violet.
Very handy for experimenting with fluorescent
phosphors.
3 x 3 inch square Price $2.55
6 x 6 inch square Prise $4.00
PRECISE MEASUREMENTS COMPANY
942 Kinds Hialiwoy. Brooklyn 23. New York
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I- -
s
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ULTRA VIOLET GENERATOR
TRIPOD MAGNIFIER
Lenses are ground for better clearity. Has high
magnification power and is adjustable by means
of a screw thread. Very popular item with ex-
perimenters, colleges and research labs.
Your Price $1.75
MICRO CIRCLE
CUTTER
FOR METAL ?
WOOD ? PLASTICS
? Micrometer type size control
? Extra heavy duty beam
? Special bea* locking
mechanism
Al all Dealers
Model
Type
Size
Pace
1
Round shank
4 inch
$5.00
1
Square shank
4 inch
5.00
5
Round shank
6 inch
7.50
PRECISE COMPANY, 942 Kings Highway
BROOKLYN 23, NEW YORK
VAN DE GRAAF MACHINE
Produces voltages between 10 KV and 100 KV.
Well designed for long life and efficient opera-
tion. Under favorable weather conditions sparks
up to three. inches can be obtained. Many in-
teresting high voltage experiments can be per-
formed with this miniature generator.
Price $15.00
12537 Angstrom units I
Consists of a miniature mercury vapor lamp in
beautiful plastic housing. Lamp constructed of
special glasses for the efficient production of
ultra violet radiation. Built in ballasts for long
life and good operation. Wavelength changer
filter instantly changes the output wavelengths
to the 3500 A band thus enabling complete
coverage of the most important bands.
Your Price $9.95
ADDITIONAL WAVELENGTH
CHANGER FILTERS
available in blue, green, yellow, orange and
red. Price $1 each
INFRA RED WAVELENGTH
CHANGER FILTERS
Converts your ultra violet generator to an infra
red generator. Price $1.50 each
NIGHT VISION GOGGLES.?These goggles
were used by the Army for nighttime
vision purposes. All are new and in indivi.
dual cloth case. Price $1.00 each
INFRARED FILM. A fortunate purchase of infrared film allows us to offer
this material at an almost unbelievable low price. Film is surplus aerial,
cameral stock which is outdated. We have tested this film and find that
good results can still be obtained. Speed rating is 50 with red filter.
Comes in vacuum sealed can in rolls 51/2 inches wide by 26 feet long.
Your Price $1.23
CESIUM VAPOR LAMPS
These lamps produce nearly a pure output of infra red light of 8521
and 8943 Angstrom units. They are the most efficient source of infra red
at these wavelengths and are about 700% more efficient than the Tung-
stem filament lamp. These lamps may be modulated up to 10,000 cycles
with voice or code. Only a very limited quantity of these lamps are
available as they were used in Navy projects. Lamps. are rated at 90
Watts at 5.5 amperes. Pries $30.00 sash.
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---? AVAI
This spectroscope is suitable for medical research, analytical work and general
purposes in physical laboratories.
The dispersion is 340 and the slit is provided with an adjustment for varying
the width. A graduated drum by which the spectrum can be moved across the
field, used in conjunction with an indicator enables readings to be taken. This
drum is divided intolOOdivisions, which are arbitrary, but which can be calibrated
if desired by the user. An adjustment is fitted for accurately focussing the
spectrum.
A table stand to carry the spectroscope can be supplied. Provision is afforded
for the attachment of a test tube holder and also a cylindrical lens attachment.
This latter is a very useful accessory, especially when working with a small or
weak source of light, as it concentrates an image of the light source on the slit:
No. 2425. Reading spectroscope, in case
? $69.50
Nos. 2458 and 2459 PRISM SPECTROSCOPES.
For certain purposes the prismatic type of spectroscope is advantageous, as it
passes very much more light than the diffraction type. The dispersion, however,
is less, and as explained in the opening description (page 1), gives a smaller relative
dispersion at the red end of the spectrum compared with that at the blue end.
This model employs a train of five prisms giving a dispersion of 100. An
adjustment is provided to the slit for varying the width ; there is also an
adjustment for accurately focussing the spectrum. The instrunaent can be
attached to a table stand, and provision is made for the attachment of a test
tube holder, etc.
No. 2459 has the addition of a comparison prism. This enables the spectra from
two sources to be examined simultaneously.
No. 2458. Prism spectroscope, in case ? ? 49.50
No. 2459. Prism spectroscope, in case ? ? 52.95
PRECISE MEASUREMENTS COMPANY Brooklyn 23, New York
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For taking direct readings in wavelengths where extreme accuracy is not
required, this instrument will be found extremely satisfactory. The dispersion
given is 10?. The scale giving readings in wavelengths ie viewed in the same
field as the spectrum, each division of the scale representing 100 A. The
slit is adjustable and the necessary focussing adjustments are provided. There
is also an adjustment to the scale so that it can be set accurately in relation
to the spectrum.
Provision for attaching to a table stand is provided and such accessories as test
tube holder and cylindrical lens attachment can be employed.
No. 2523 has the addition of a comparison prism. This enables the spectrum
being examined to be compared with a standard or other source.
No. 2522. Prism spectroscope, in case ..
?$$9849?3500
No. 2523. Prism spectroscope, in case ..
ACCESSORIES
TABLE STAND.
This stand is strongly made, the spread of the feet is arranged to ensure that
the stand is rigid. The fitting carrying the spectroscope has adjustments for
raising and lowering, also for tilting, both adjustments being provided with
clamps. It is suitable for spectroscopes Nos. 2447, 2449, 2425, 2426, 3500,
2458, 2459, 2522, 2523. 2435 and 2438.
No. 2437. Table stand . . . . $995
CYLINDRICAL LENS ATTACHMENT.
When small or weak sources of light are being
examined, this attachment is found extremely
useful, as it produces an extended image of the
light source on the slit. It can be used in con-
junction with Nos. 2447, 2449, 2425, 2426, 3500,
2458, 2459, 2522 and 2523.
No. 2496. Cylindrical lens $950
attachment . .
CYLINDRICAL LENS ATTACHMENT.
This attachment is on the same principle as No. 2496, but is made in quartz so
that it can be used in conjunction with spectroscopes Nos. 2435 and 2438.
No. 2436. Cylindrical lens attachment ? . ? . ? ? $1 095
TEST TUBE HOLDER.
This holder is a secure method of supporting a test
tube and enables a number of tubes to be easily and
quickly changed. It is attached to the spectroscope
by two clamping screws and can be used on models
Nos. 2447, 2449, 2425, 2426, 2458, 2459, 2522 and
2523.
No. 2697. Test tube holder .
.. $2.95
, PRECISE MEASUREMENTS COMPANY Brooklyn 23, New York
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I pl Ilii LfLL L
Declass fied in Part - Sanitized Copy Approved for Release 2011/12/28: CIA-RDP78-03300A001600020097-5
IlUb. GY.30 UI.. 1 MA 1
Declassified
This is a compact spectroscope for the examination of the ultra violet spectrum
Its general design can be seen by the illustration. It has an accurately made
slit, fixed or adjustable, through which the light passes on to a quartz prism,
'forming a spectrum upon a fluorescent screen. The spectrum thus formed is
examined by an eyepiece, giving a magnified image. The eyepiece is provided
with a focussing motion and an. eye cup to exclude extraneous light.
Beside the spectrum in the field of view is an illuminated
scale, divided in Angstrom units, so that the wavelength of
any portion of the spectrum under observation can be deter-
mined. The scale appears With illuminated lines and figures
upon a black background, the illumination being obtained
through a window in the instrument by means of the visible
light in the light source under examination, so that no add-
itional source of light for illuminating the scale is necessary.
The spectrum included in the field of view is from 2,000
A. to 4,500 A.,. which includes a small portion of the
visible light.
The instrument can be conveniently used in the hand, table
stand can be supplied if required
This spectroscope has been designed with a view to giving
a particularly brilliant Spectrum, thus rendering it easily
used in daylight and with the same ease as a spectroscope
for visual light. It is, therefore, specially useful for rapid
Spa, k spectrum of zinc
determinations in electromedical and similar establishments and cadmium as seen in
and for industrial workshop use, when a more complicated eyepiece of speciroscope.
apparatus is inconvenient to use.
When a small source of light is being examined, the brilliancy of the spectrum
Can be increased by using a cylindrical lens attachment (page 12), thus making
it unnecessary to hold the spectroscope close to the source of light.
No. 2435. ultra violet spectroscope, in case .. . . 109.50
No, 2438. - ultra violet spectroscope with adjustable slit,
in case .. 114.50
PRECISE MEASUREMENTS COMPANY Rrnnlelvn v?..L
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1 I
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This is a very convenient pocket spectroscope for general purposes and students,
use, having a dispersion of 200. The slit is of a fixed width, protected by a glass
cover to prevent dust from entering. An adjustment for accurately focussing
the spectrum is provided.
No. 2444. Pocket spectroscope, in case
the menlo 7eueveetem
battery powered, in this pro?
fessional instrument case
with six different speci-
men -holding end
caps ; choice of
long or short wave
operation ? complete:
$49.50. Fluoretor for II5-v
60-cycle power: $42.00. Inter-
changeable lamp for 'alternate
wavelength: $20.00.
Our Price $12.50
"'hobbles
The Fluoretor makes many
hobbies more enjoyable.
Mineral collectors use it in
the discovery of fluorescent
specimens in the field and
to enhance displays of their
collections. Philatelists
:identify papers, cancella-
tions, ink variations, stir-
prints and Eorgeries. '
chemical
testing
Both quantitative and
? qualitative chemical checks
are made in or out of the
laboratory with light,
convenient Fluoretor. Inval-
uable in smaller labora-
tories. Long or short wave,
choice of battery or electric
outlet power.
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I I I I I I IL I-I.1 II II I. I I 111 I u
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Rush Order Blank
Name Date
Street Address or Rural Route Box No
Town Zone State
QUANTITY
DESCRIPTION
PRICE
PER
AMOUNT
MINIMUM ORDER 50 CENTS. MATERIAL IS SHIPPED POSTPAID TO ANY
POINT IN U. S. A. UNLESS MARKED OTHERWISE. CANADIAN AND FOREIGN
ORDERS ADD 10% TO COVER COST OF ADDITIONAL PACKING. REMIT BY
MONEY ORDER OR POSTAL NOTES.
PRECISE MEASUREMENTS COMPANY
942 Kings Highway, Brooklyn 23, New York
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I I I
I--
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Rush Order Blank
Name Date
Street Address or Rural Route Box No
Town Zone State
QUANTITY DESCRIPTION PRICE PER AMOUNT
MINIMUM ORDER 50 CENTS. MATERIAL IS SHIPPED POSTPAID TO ANY
POINT IN U. S. A. UNLESS MARKED OTHERWISE. CANADIAN AND FOREIGN
ORDERS ADD 10% TO COVER COST OF ADDITIONAL PACKING. REMIT BY
MONEY ORDER OR POSTAL NOTES.
PRECISE MEASUREMENTS COMPANY
942 Kings Highway, Brooklyn 23, New. York
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Declassified in Part - Sanitized Copy Approved for Release 2011/12/28: CIA-RDP78-03300A001600020097-5
VIBRATOR
ANSFORNR.ERS
IGNITION COIL?This miniature high volt-
age coil provides high output for snooper-
scope operation. Has built in condenser
for extra power.
GE OZONE LAMP
Generates short ultraviolet
radiation (1849A & 2537A) which
produces ozone by converting
the oxygen of the air (02) into
ozone (0l). Useful for fluores-
cent & phosphorescent ma-
terials. Uses only 4 watts of
power. Lamp supplied with
socket and instructions.
Your Price $1.95
FLUORESCENT PIGMENTS
Brightest glowing, concentrated phosphors, avail-
able in many colors. Red, White, Blue, Green, Yel-
low and Orange. Mix with clear lacquer for painting.
SAMPLE SIZE (specify color) 15c each
COMPLETE SAMPLE KIT (6 colors) $1.75 each
Oar Ounce Bottles (opacity color) 511c each
No. 2444 POCKET DIFFRACTION
SPECTROSCOPE
This is a very convenient pocket spectro-
scope for general purposes and students' use,
having. a dispersion of 20". The slit is of a
fixed width, protected by a glass cover to
prevent dust from entering. An adjustment
tor accurately focussing the spectrum is pro-
vided. Not a toy but a scientific instrument.
Available for the first time in small size_
No. 2444. Pocket spectroscope, in leather case.
Special 412.50 (while they last)
"Little Wonder"
RADIO RECEIVING SET
Compact in size but big in results. The
open type detector permits adjust-
ments to be made to the finest degree.
This set includes the Philmore Super-
sensitive Crystal which assures quick
results when "looking" for a station,
because the entire surface of the crys-
tal is sensitive.
Cat. No. 7000
Price $1.75
Plus Federal Excise Tax
HIGH VOLTAGE
TRANSFORMER
Pt-i. 115 v. 50-60 ey. ;lee. 4500V. 2MA
o2: 2,5v 9
$795
Postpaid
in U.S.A.
"Supertone"
RADIO RECEIVING SET
A remarkable Radio Receiving Set
built to give everlasting service.. This
set will bring in broadcasting loud
and clear without distortion or noises.
The Supertone Crystal Set is equipped
with a Rhilmore Supersensitive Crys-
tal which will give excellent results
over an indefinite period of time.
Cat. No. 7001 Price $2.25
Plus Federal Excise Tax
NIGHT VISION GOGGLES.?These goggles
were used by the Army for nighttime
vision purposes. All are new and in indivi-
dual cloth case. Price $1.00 each
AERIAL KIT
A complete kit of parts
for assembly of a profes-
sional antenna. Attrac-
tively packaged in a
multi-colored display box.
1 coil 7-26-50 ft. stranded
copper aerial wire.
1 coil 25 ft. rubber coy.
ere. lead-in wire.
1 Ground Clamp.
1 Lead-in-strip.
2 Porcelain insulators,
2 Nail-it knobs.
1 Instruction sheet.
Cat. No. 2103 Price $1.50
Declassified in Part - Sanitized Copy Approved for Release 2011/12/28: CIA-RDP78-03300A001600020097-5
Declassified in Part - Sanitized Copy Approved for Release 2011/12/28: CIA-RDP78-03300A001600020097-5
VIBRATOR
ANSFORNR.ERS
IGNITION COIL?This miniature high volt-
age coil provides high output for snooper-
scope operation. Has built in condenser
for extra power.
GE OZONE LAMP
Generates short ultraviolet
radiation (1849A & 2537A) which
produces ozone by converting
the oxygen of the air (02) into
ozone (0l). Useful for fluores-
cent & phosphorescent ma-
terials. Uses only 4 watts of
power. Lamp supplied with
socket and instructions.
Your Price $1.95
FLUORESCENT PIGMENTS
Brightest glowing, concentrated phosphors, avail-
able in many colors. Red, White, Blue, Green, Yel-
low and Orange. Mix with clear lacquer for painting.
SAMPLE SIZE (specify color) 15c each
COMPLETE SAMPLE KIT (6 colors) $1.75 each
Oar Ounce Bottles (opacity color) 511c each
No. 2444 POCKET DIFFRACTION
SPECTROSCOPE
This is a very convenient pocket spectro-
scope for general purposes and students' use,
having. a dispersion of 20". The slit is of a
fixed width, protected by a glass cover to
prevent dust from entering. An adjustment
tor accurately focussing the spectrum is pro-
vided. Not a toy but a scientific instrument.
Available for the first time in small size_
No. 2444. Pocket spectroscope, in leather case.
Special 412.50 (while they last)
"Little Wonder"
RADIO RECEIVING SET
Compact in size but big in results. The
open type detector permits adjust-
ments to be made to the finest degree.
This set includes the Philmore Super-
sensitive Crystal which assures quick
results when "looking" for a station,
because the entire surface of the crys-
tal is sensitive.
Cat. No. 7000
Price $1.75
Plus Federal Excise Tax
HIGH VOLTAGE
TRANSFORMER
Pt-i. 115 v. 50-60 ey. ;lee. 4500V. 2MA
o2: 2,5v 9
$795
Postpaid
in U.S.A.
"Supertone"
RADIO RECEIVING SET
A remarkable Radio Receiving Set
built to give everlasting service.. This
set will bring in broadcasting loud
and clear without distortion or noises.
The Supertone Crystal Set is equipped
with a Rhilmore Supersensitive Crys-
tal which will give excellent results
over an indefinite period of time.
Cat. No. 7001 Price $2.25
Plus Federal Excise Tax
NIGHT VISION GOGGLES.?These goggles
were used by the Army for nighttime
vision purposes. All are new and in indivi-
dual cloth case. Price $1.00 each
AERIAL KIT
A complete kit of parts
for assembly of a profes-
sional antenna. Attrac-
tively packaged in a
multi-colored display box.
1 coil 7-26-50 ft. stranded
copper aerial wire.
1 coil 25 ft. rubber coy.
ere. lead-in wire.
1 Ground Clamp.
1 Lead-in-strip.
2 Porcelain insulators,
2 Nail-it knobs.
1 Instruction sheet.
Cat. No. 2103 Price $1.50
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Declassified in Part - Sanitized Copy Approved for Release 2011/12/28: CIA-RDP78-03300A001600020097-5
Assembly of the tripod is strairhtforward. The longer set of le gs
engage the set of holes farthest apart.
to form a point at the lower end.
The kegs should be unfolded
BATTER/. CHARGER AND BATTERIES
When a substantial portion of the ampere hour capacity of the
batteries has been discharged, the batteries should be recharged. To doso
remove the front cover and plug the line cord intba 115 AC line.
( A link is provided in case 041230 VAC is available) Turn the function
switch to position "C" and depress the charge start switch button which
is located near the modulation indicator light. The indicator light will
be lit and will remain lit as long as the chnrger is in operation. It
may be necessary to depress the start button for several seconds due to
capacity in the relay circuit.of the charger. If the charFcr fails to
remain in operation upon relaease of the start button after several attempts
this indicates that the batteries are very close to a fully charged
condition. The charger will cut off automatically when the battery
potential has risen to a fully charged condition. It requires approximately
12 to 14 hours to charge a set of r hi ar ccmpLetely
The equipment should be kept in an upright position while the charger is
in pperation if this is possible.
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Declassified in Part - Sanitized Copy Approved for Release 2011/12/28: CIA-RDP78-03300A001600020097-5
As a result of some field testing of the equipment by the manufacturer,
the following procedures are recommended for establishing donta'ct
between two units.
Since the viewers are not as effective in daylight as they are
in darkness, initial familiarization will probably best be done at night
at moderate ranges( two or three miles)
It is assumed that the watches of the operators have been
synchronized and that some particular time has been designated for
the establishment of contact.
NIGHT OPERATION
1. Both units are assembled for operation, the legs are attached to
the table and the unit is mounted in the yoke.
2. The scan mechanism is disabled by running through a complete
scan ( three sweeps to the left alternated with three sweeps to the
right) In this condition, the instrIonnt does not change its angle
of elevation with further horizontal scanning.
3. The angle of elevation is then set approximately and the wing nuts
at the side of the unit are tightened to the yoke. The azimuth setting
is adjusted so that sweeping will cover the area in which the other
unit is believed to be located.
4. The Function Switch is turned to "F".
5. The R-T Swittivis turned to R.
6. The viewer charging switch, located just to the right of the eyepiece
is depressed, and held depressed until li hts in the vicinity form
sharp green points on the viewer screen, or if there are no lights
moon , or sometimes even stars wifl suffices Keep- the switch derressed
for 5 to 10 seconds.
7, At the desir7nated time onerator A turns his R-T switch to T and
slowly scans the area in 1.,q}nich operator B is supPosed to be located.
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Declassified in Part - Sanitized Copy Approved for Release 2011/12/28: CIA-RDP78-03300A001600020097-5
Operator A also watches through his viewer for the appearance of the
light of operator B, and continues scanning until this light appears.
8. Operator B watches through his jewer for a flashing light. The
duration of the flash will denend on the sneed of A's sweeping, and
the brightness will depend on the accuracy of alignment as well as range.
At the specified initial test range of 2 or 3 miles, the light will
probably be brighter thn any other light visible.
9. When B sees what he thinks is the light of A, he turns his unit
so that the light falls within the reticle of his viewer. (With some
tubes, the background brightness is so low that the reticle will be
seen only with difficulty. In this case the image is brour-ht to the
center of the screen as judged by the onerator) The azimuth setting
is then carefully adjusted for maximum loudness of the 1000 cycle
note that will be heard with each flash. Because of the nature
of the source (i.e. not steady) this adjustment will probably not be
exact, but will probably be sufficiently close.
10. When the adjustment (9.) has been completed, B turns his R-T Switch
to T.
11. When B comnletes step (10.) A will see the light of B in the
viewer of the A unit. When this light anears, he turns his 7Z-T switch
to R and adjusts his azimuth setting for maximum loudness of the
1000 cycle tone bein- transmitted bY B. Since the B transmitter is
fixed, A can make this adjustment with considerable accuracy. He also
will "touch up" the elevation adjustment, again for maximum loudness
of B's signal.
12. When A has completed step (11.) he turns his R-T switch to T.
He again watches his viewer for the apearance of B's
13. B, when he sees A's light according to (12.) turns his R-T switch
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Declassified in Part - Sanitized Copy Approved for Release 2011/12/28: CIA-RDP78-03300A001600020097-5
to R, and makes final touch-un adjustments to his dizimuth and elevation
settings. This time B has a steady tone on which to align, and so
can do this alignment with accuracy.
14. When B has completed his alignment, he turns his function switch to
OP, and his R-T switch to T, and then starts communication.
15. When A sees B'S lamp in (14) he turas his R-T switch to R and
his Function switch to OP.
After the initial alignment has been completed, the viewers need
not be used, however it has been found that if they are used, "Break-in"
operation is possible. That is, when the person who is transmitting
sees the lamp of the other in his viewer, he knous that he should
go into the R condition.
DAYTIME OPERATION
The procedure for the first seven steps are as above, except that
?robabts,
because of the high brightness of the landscape, AAwill not be able to
see the light of operator B at any time. The siewerris still useful
if the collimation of it wibh the unit is known since the unit can
now be quite accurately aimed at any reference landmarks that may be
known.
8. During the course of his scanning, operator A must interrupt the
transmission to listen for B. It is suggested that after each minute
or two of scanning with the R-T Switch in the T position, operator A
should make a complete scan with the R-T switch in the R position.
9. Operator B leaves his R*T switch in the R position, and slowly,
very much more slowly than A, scans the area in which A is believed to be
located. If A completes a horizontal scan in three or four seconds
or less, a scan by B should take not less than 30 seconds. Actually
the B scan should consist of a series of finite steps, each about 1/3
or less of the diameter of the reticle. Obviously, if B knows the
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Declassified in Part - Sanitized Copy Approved for Release 2011/12/28: CIA-RDP78-03300A001600020097-5
location of A quite accurately, he will have a smaller range of
scan to make.
9a. If B does not hear A's tone after two scans, he should change
the elevation by approximately 1/3 the height of the reticle and
repeat step 9 until the B unit is aimed for the best loudness of
the A tone.
10. B locks his unit and turns his R-T Switch to T.X074), At the end
of each minute for three minutes he listens, i.e. Turns the R-T switch
to R and listens for a steady tone signal ( as compared to the pulses
of the 1000 cycle tone heard during the A scan()
11. If A hears a tonefom B's transmitter on one of his "listening
scans", A immediately aligns his instrument for loudest signal. This
will involve both azimuth and elevation fine adliustment. When his
unit is aligned, A turns his R-T Switch to T. Eat. vAthAO tLereAr
A turns lANe su3rtcv% 4.0 it +or 10 -tC Secon45.
12. When B hears a steady fone from A, he makes fine adjustments on
his azimuth and elevation settings for maximum loudness of signal.
The signal will be turned off after some period of time which should
not exceed 1 minute. When the signal frank ceases, B turns his R-T
switch to T and his function switch to OF, and starts communication.
13. When A hears voice modulation from B during his listening period
as mentioned in (it) he turns his function switch to OF, and continues
communication.
Since the viewers are not able to distinguish the transmitter
from the background during daytime operation, Break-in operation is
not possible, but each oneratchr must wait until the other has finished
his transmission.
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Declassified in Part - Sanitized Copy Approved for Release 2011/12/28: CIA-RDP78-03300A001600020097-5
- -
REPLACEMENT OF COVERS
Care should be used Inane replacing the covers to prevent distortion of
the draw pull catches. The catches should all be fully extended before
any are latched in order to Prevent the catch from beinp wedged under-
neath the gasket. The catches on opposite sides of the cover should be
latched in pairs for best results. Make sure that the locating tabs
on the center section do not extend into the gasket groove. The tabs
should pass to the inside of the innermost flange. Screw the occular
of the viewer inward before replacing the tripod platform. The
microphone may be wedged into the compartment against the arms of the
bellows mechanism to Prebent rattle. The covers are stamped with
serial numbers and should be replaced only on the corresponding units.
, I Declassified in Part - Sanitized Copy Approved for Release 2011/12/28: CIA-RDP78-03300A001600020097-5
L
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/4
?
/ .?1,416 -loco
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L9ZI ON 01 X 01 339
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