RESEARCH ORDER #1 PHASE I - PROGRESS REPORT #4
Document Type:
Collection:
Document Number (FOIA) /ESDN (CREST):
CIA-RDP78-03300A001600020106-4
Release Decision:
RIPPUB
Original Classification:
C
Document Page Count:
8
Document Creation Date:
December 22, 2016
Document Release Date:
December 28, 2011
Sequence Number:
106
Case Number:
Publication Date:
April 7, 1954
Content Type:
REPORT
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CO H DENN 1- 1 AL1
Research Order #1 7 April 1954
Phase I - Progress Report #4
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Page 1 of 7 page s
Research Order #1
Phase I - Progress Report #4
7 April 1954
To study and evaluate the factors and components
involved in the design of a portable infrared communicator.
The work to be performed according to Bid Proposal
#76-1, Phase I, may be summarized as follows:
A. Evaluation of sources and sensitive elements
B. Determination of beam width requirements and
evaluation of "find-operate" systems
C. Study of modulation methods and attendant optical
systems
D. Evaluation of power sources
E. Study of required circuit characteristics
The results of these studies will be used as the basis
for recommending a system to be developed.
DETAILED DATA:
A. Evaluation of sources and sensitive elements
Investigation of sources has been centered about
tungsten filaments and zirconium arcs with the following results:
First it should be pointed out that the transmitter
can be analyzed in a manner identical to the analysis of searchlight
systems; that is, since a luminous source is to be placed at the
focal point of an optical system, and the resultant beam has small
angular width, the net result (neglecting modulation) is no
different from an automobile spotlight or a 60 inch searchlight
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Page 2 of 7 pages
Research Order #1 7 April 1954 AL'I Phase I - Progress Report #4
insofar as illumination is concerned. The theory of searchlights
has been well covered in the literature', but the important result
for our application is that the illumination produced by a searchlight
at a point on its axis is equal to that which would be produced by
a source of the same size as the exit pupil (normally the searchlight
reflector) and having the same brightness as the original source.
The product of the area of the exit pupil and the brightness of
the source is called the beam candle power, and the illumination
produced is directly proportional to this value.
Since the illumination at the receiver determines
the signal value, it is of prime importance to maximize the beam
candle power of the transmitter. Extending the size of the source
does not increase the beam candle power if its brightness is kept
constant; it is of importance, however, in determining the angular
width of the beam thru which the beam candle power is a maximum.
Also, if mechanical modulation is used, problems involved are
proportional to the source size.
Thus for our application it is of prime importance
to consider the brightness of the source and the diameter of the
optics. The focal length of the optics and the size of the source
together will determine the beam width, according to the approximate
formula W'l' 57. 2 degrees. Conversely, if the beam width
and focal length are given, the source size is immediately dictated.
Size considerations have restricted our thinking to
a maximum diameter of 10 inches and a focal length in the range
of 6 to 10 inches for the optics. The necessary beam width has
not been derived, but we believe it will be in the neighborhood
of one degree. The resulting source size then is from 0. 100 to
0. 180 inch.
1JOLLEY, WALDRAM & WILSON: "The Theory & Design Of Illuminating
Engineering Equipment", Wiley, 1931.
HARDY & PERRIN: "The Principles Of Optics", McGraw-Hill, 1932.
JENKINS & WHITE: "Fund-Of Optics", 2d ed., McGraw-Hill, 1950
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Page 3 of 7 pages
G~~~~v IAL
Research Order #1 7 April 1954
Phase I - Progress Report #4
The characteristics of three zirconium arcs are
given below:
Power
Size
Brightness
Life
2 watts
.003"
9, 620 C/cm2
175 hrs.
10 watts
. 016
5, 500 C/cm2
700 hrs.
25 watts
.029
4, 030 C/cm2
800 hrs.
It is seen that even the largest of these falls far below
the minimum tentative size requirement. It is possible to increase the
effective size of the source by at least two schemes, but one of these
decreases the net beam candle power, and the other imposes require-
ments on the optical system which are not feasible at such low focal
ratios as we are considering. Such a lamp would be ideal for use
once contact were established because the narrow beam greatly improves
security.
The life indicated for these lamps is quite favorable
as is the extraordinary brightness. . The brightness of any of the lamps
can be increased even further at the expense of life. Their small size
makes them ideal for mechanical modulation.
In Volume 4 of the Summary Technical Report of
Division 16, NDRC (1946) is listed a majority of the tungsten lamps
used during World War II for infrared applications. Of the many listed
one appears to have possibilities for our use. Its characteristics are:
Power: 30 W
Size: 1 mm x 7 mm (approx.)
Brightness: 2100 9cm2 *
Life: 30 hours
This size filament would form a beam of approximate dimensions
1 /3? x 2-1/2o with 6" focal length optics when oriented perpendicular
* based on an approximate color temperature of 3, 300 K.
CONFIDENTIAL
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Page 4 of 7 pages
Uri
I ENTIALL
Research Order #1 7 April 1954
Phase I - Progress Report #4
to the optical axis. If the coil axis were made coincident with
the optical axis, the beam would be symmetric and about 1/20
across.
This lamp is the type 1045 and was used in the
production model snooperscope and sniperscope. It represents
about the maximum brightness that can be obtained consistent
with reasonable life and power. However, by over running the
lamp, the brightness can be increased approximately 20% for
every 50% reduction in life. Thus, for a rated 15 hour life the
brightness of this filament might be increased to 2, 500 Cf cm .
From an optical standpoint, the zirconium arc has
everything in its favor but its size. Its brightness exceeds twice
that of the tungsten filament, and its life is twenty times greater.
Overall size of the lamps is nearly the same in either case,
although the tungsten lamp is slightly smaller and more adaptable
to reflective optics.
The main disadvantage of the zirconium arc is that
it requires an initial starting pulse of at least 1, 000 volts and a
ballasted operating power supply of at least 50 volts for stability.
Tungsten filament on the other hand, of course, can be designed
to operate at practically any combination of current and voltage,
and the coil can ordinarily be wound to a desirable size.
When a coiled filament is used as the source in a
system however, the illumination across the generated beam is
very non-uniform, the effect being caused by the space between
adjacent filaments. This condition does not exist in the zirconium
arc, since the source here is a spot of high brightness across its
entire face.
In spite of its superior optical characteristics, the
electrical difficulties of the zirconium arc plus its small Source size
will probably preclude its use in our design.
CONFIDENTIAL
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Page 5 of 7 pages
~ITIAL
Research Order #1 L,;' ~. 7 April 1954
Phase I - Progress Report #4
B. Determination of beam width requirements and evaluation of
"find-operate" systems
The darkroom is presently in use for beam width
studies. Apparatus was set up in the last few days of this period
and is now being debugged. Decade amplifiers may have to be
used with the gear to improve signal response.
C. Study of modulation methods and attendant optical systems
Further study has been made of the problems involved
in mechanical modulation systems. In general there must be a
compromise between great optical magnification of the motion of
the modulated surface and a compact, rugged construction
necessary to maintain linearity and modulation percentage under
field conditions. As explained in section"E" (below) a system of
non-linear modulation is being considered. This system would
require 100% modulation on all frequencies, and the difficulties
in achieving this might more than overcome those involved in
maintaining good linearity in a system using a variable modulation
percentage.
The general limits on the size and displacement of
the modulated surface are being set on the basis of theoretical
studies. When these are completed, a transducer capable of
supplying the motion will be chosen, and an appropriate optical
system built up for tests.
D. Evaluation of power sources
An order has been placed with Motoresearch Company,
of Racine, Wisconsin, for two alternators to the following
specifications:
1.
Mechanical input:
100 watts at 12, 000 rpm
2.
Electrical output:
6. 3 v, 9 amp., and 220 v,
100 ma at 800 cps
3.
Voltage regulation:
5%
CO N rI D ENTIAL
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Page 6 of 7 pages
Research Order #1 7 April 1954
Phase I - Progress Report #4
4. Wave form: 1016 total harmonic distortion
5. Rotor to withstand: 15, 000 rpm rotation
6. Size: 12 cu. in. maximum volume
1. 5 lb s . maximum weight
While this specification was set up primarily for a system
using a tungsten source and mechanical modulation, the
alternator frame could be adapted to voltages required by
other sources and modulation methods. The cost of two units
will be $2, 235, and delivery is expected by July 1.
has completed delivery of the four
engines ordered for test. A preliminary check of the silenced
engine (which consists of a special silencer to which a standard
engine is fitted) indicates that, while the reduction of exhaust
noise is great, a further reduction will be required for our
application. Complete tests will be made when a suitable test
stand has been fabricated.
E. Study of required circuit characteristics
A study is being made of the system of non-linear
speech transmission reported in the "Proceedings of the Symposium
On The Application Of Transistors To Military Electronic Equip-
ment, at Yale, September 1953. " This system is based on the
observation that most of the intelligence is contained in the time
relationships of the zero-crossings of the speech wave form.
The speech signal is differentiated, and the resultant used to
trigger a flip-flop. The pulse output (which amounts to "infinite
clipping" of the input signal) is transmitted through whatever
band pass would normally be used. At the receiving end
integration restores a fairly normal sound.
It is claimed that this system gives intelligibility at
signal-to-noise ratios of 1 or less. When applied to a mechanical
modulation system, it would make it unnecessary to maintain
linearity of modulation, which is normally quite difficult to achieve
over reasonable dynamic range. The disadvantage, as pointed
CQ "F! ENTIAL~~
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Page 7 of 7 pages
Research Order #1
Phase I - Progress Report #
E h4L 7 April 1954
out above (C), is that the non-linear system calls for a capability
of 100% modulation over the pass band.
Equipment necessary to test the system has been
ordered or is already on hand. Tests will be coordinated with
the modulator studies.
Beam width tests will continue. Theoretical studies
will be pushed far enough to make possible some tests of electro-
mechanical transducers for use as modulators.
Report prepared by
Report approved by
Report approved by
DENTIAL,
DHW/t
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