ELECTRO-OPTICAL SYSTEM

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP81-00120R000100060044-3
• Release Decision: RIFPUB
• Original Classification: K
• Document Page Count: 6
• Document Creation Date: December 20, 2016
• Document Release Date: November 6, 2002
• Sequence Number: 44
• Publication Date: October 31, 1961
• Content Type: CONT

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Oct. 31, 1,961
Filed'" 8. 1947
ti
W. HERRIOTT
ECECTRO-OPTICAL SYSTEM
3,006,234
A
. `J
L
. INVENTOR
W. HERRIOTT
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` Oct. 31, 1961
Filed Nov. 8, 1947
W. HERRIOTT
ELECTRO-OPTICAL SYSTEM
3',006,234
V Q O
2 Sheets--Sheet 2
/NVENTOR
BV W. HERR/OTT
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 Approved For Release 20007/09/21: CIA-RDP81-0012OR000100060044-3 3,QQ6,234
States Patent Office Patented Oct. 31, 1961
1 2
3,006,234 returned by the distant target is applied to the vertical
SYSTEM deflecting plates of the cathode ray oscilloscope and the
ELECTRI)-OP 06 34
William Herriott, Chatham, N.J., assignor to Bell Tele- time sweep wave initiated by the synchronizing pulse is
phone Laboratories, Incorporated, New York, N.Y., a applied to the horizontal deflecting plates.
corporation of New York 5 As a modification, a multiplicity of weak prisms can
Filed Nov. 8, 1947, Ser. No. 784,925 be employed for the purpose of securing more than one
10 Claims. (Cl. 88--1) pulse which may precede or follow the main pulse at
equal or'unequal time intervals. By way of example,
This invention relates to electro-optical systems and one prism can be placed at the lower end of the undis-
more specifically to object locating and distance measur- 10 placed image of the lamp in the plane of the scanning
ing systems employing ' light.- - - - disc and the second prism placed in the path of the rays
The term "light," as used herein, is intended to be forming the upper end of its undisplaced image.
descriptive of radiation in both the visible and invisible The invention will be more readily understood by
portions of the spectrum. referring to the following description taken in connec-
In a copending application of E. Bruce, Serial No. Ib tion with the accompanying drawings forming a part
775,685 filed September 23, 1947, now U.S. Patent No. thereof in which:
2,970,310, there is disclosed an object locating and dis- FIG. I is a schematic diagram of an object locating
tance measuring system employing light waves, prefer- and distance measuring system employing light radi-
ably infra-red light rays. In the arrangement described ation and utilizing an electro-optical arrangement in ac-
in the Bruce application, a light pulse from a flash lamp 20 cordance with the invention for producing light pulses;
is reflected by a paraboloidal mirror directed toward a FIG. 2 is a perspective view of a portion of the system
target (which is preferably a retrodirective reflector), shown in FIG. 1;
and echoes or reflections therefrom are picked up by a FIGS. 3 and 4 are diagrammatic representations to aid
receiver optical system and applied to a photomultiplier. in understanding the invention;
The amplified output of the photomultiplier is applied to 25 FIG. 5 is a perspective view of a portion of a modified
the vertical deflecting plates of a cathode ray oscillo- electro-optical system; and
scope to tie horizontal deflecting plates of which is ap- FIG. 6 illustrates on the screen of a cathode ray oscillo.
plied a timing sweep wave initiated by a synchronizing scope an echo pulse and a range mark pulse.
pulse produced at the same time as the light pulse. This Referring more specifically to the drawings, FIG. 1
synchronizing pulse is also utilized to produce a range 90 shows by way of example for purposes of illustration,
mark of known time delay for indicating distance to the an object locating and distance measuring system ern--
target. The present invention is concerned with an elec- ploying visible or invisible light rays. When infra red
tro-optical system of the same general type as that dis- light is used, the system is frequently called an `rra:i."
closed in the Bruce application but which utilizes instead The optical system for the main beam comprises a con.
of a flash lamp a constantly emitting light source, 85 stantly emitting tungsten lamp 10 which produces radi-
It is an object of this invention to utilize a constantly ation in both the visible and invisible
emitting tungsten light source to produce light pulses spectrum, a lens system represented by the single lens
for object locating and distance measuring systems. 11 for focussing an image of the narrow straight filament
It is another object of this invention to produce by 12 of the lamp 10 on the plane of a rotating disc 13,
refractive optical means a synchronizing pulse just pre- 40 an optical system comprising a lens system 15 and
ceding (or following) each pulse of light directed to mirror 16 for directing radiation from the lamp 19 upon
the target of an object locating distance measuring a target 17 (shown as a retrodirective reflector) which
system. returns some of this radiation to a receiver optical sys-
Other objects and features of the invention will be tem, comprising the paraboloidal mirror 18, which focuses
apparent as the description proceeds. 4,5 the received radiation upon the cathode of a photomul-
In a specific illustrative embodiment of the invention, tiplier 19 which produces an electrical pulse utilized for
infra-red light rays are used. A continuous beam of determining the range of the target. The optical sys-
these rays is produced by a constantly emitting tungsten tem also includes means for producing a "preknock"
light source having a narrow, line-like filament and this synchronizing pulse by means of light passing through
source is associated with a moving optical system for 5o the prism 10, the moving slit 14 in the disc 13, and the
generating an electrical pulse leading the transmission right angle prism 21 and incident upon a photocell 22,
of an infra-red pulse which is reflected by a mirror thus producing an electrical synchronizing pulse. The
and directed toward a target, preferably a retrodirective pulse produced in the photocell 22 is applied to a sweep
reflector. Reflections of the target are picked up by a and beam brightening voltage generator 24 to initiate
receiver optical system and applied to a photomultiplier. 45 a time sweep in the tube 23 and also to produce a
The outgoing light pulses are produced by rotating a voltage which can be applied to the control element 25
disc or wheel having a narrow slit or slits therein in the of the tube 23 to "unblank" the blocked off beam for
plane of an image of the tungsten source formed by a the duration of the sweep. A suitable sweep and ;.;.,-u
suitable lens or lens system. brightening (unbianking) circuit is disclosed in an ap-
..
the main image which is intercepted by the moving slit chronizing pulse produced in the photocell 22 is .aiso
slightly ahead of or behind the main image depending applied to a range unit 27 to produce a range mark
after passing through the movin,.z slit is directed by means amplifier 29 receiving the output of the photomu?t'o].;,?r
of a right angle total reflecting prism and a lens to the 19 and of the range unit 27 and the pair of deP,et t:., g
cathode of a photocell which generates a synchronizing plates: 28 are connected in a series circuit so that the
pulse: which can be used for triggering a sweep circuit To range mark pulse optionally is either added to or sub-
in an oscilloscope forming a part of the system. The tracted from the amplified received pulse of corresporrd-
amplified output of the photomultiplier receiving the rays ing time delay, depending on the polarities of the pulses.
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3 8,00e5284
A suitable range unit. is disclosed in an application of displaced and the displaced segments of the filament
L. A. Meacham, Serial No. 491,791, filed June 22, 1943, image 10. An increase of distance between the prism
which issued on June 17, 1947 as Patent 2,422,204, or 20 and the slit wheel 13 causes an increase in distance
in an article entitled "The SCR-584 Radar" in the between the two segments of the filament image 30 with
February 1946 issue of "Electronics," beginning on page 5 consequent increase in the length of time by which the
110. phototube 22 response anticipates the main target pulse.
Reference will now be made to FIG. 2 which shows FIG. 3 shows a ray of light entering prism 20 in position
schematically that part of the optical system represented A and deviated toward the prism base to the plane of
within the dashed lines in FIG. 1. For a better under- the slit wheel 13 which it intersects at point C. If, how-
standing of the relationship of the various elements, they 10 ever, the same prism is placed in position B (shown in
have been shown in perspective. An image of the linear dot-dash line in FIG. 3) the deviated ray will intercept
filament 12 is focussed by the lens system 11 upon the the plane' of the slit wheel at point D. The undeviated
plane of the disc 13 which is rotating in the direction ray or main beam will, of course, intercept the plane of
of the arrow. This disc has one or more slits 14. If the slit wheel 13 at point 0. Hence the length 0-C
a plurality of slits are used, they are symmetrically ar- 15 represents one period of time by which the response of
ranged if it is desired to have the pulses evenly spaced, the phototube 22 will precede the main target pulse
but if it is desired to have an uneven arrangement of produced by the light passing through the lens 15 and
pulses the slits 14 are non-symmetrically positioned on reflected toward the target 17 by the mirror 16. The
the disc 13. By way of example, if two slits 14 are used length O-D represents a second period of time in the
they may be placed 150 degrees apart rather than in a 20 same sense. If for any reason it is desired to have the
symmetrical arrangement having 180 degrees separation; response of the phototube 22 follow the main pulse
this non-symmetrical positioning produces an uneven ar- instead of precede it, this can readily be done by a re-
rangement of pulses with respect to time. The length versal of the direction of rotation of the slit wheel 13
and shape of the pulse of light produced on the side or by reversal of the position of the deviating prism 20
of the disc remote from the lamp 10 depends on the 25 (in the sense that it is turned through 180 degrees, as
size of the image 30 of the wire filament 12, and the shown in FIG. 4). Here the displaced images lie at
width of the slit 14 and the speed of the disc 13 are points C' and D' for prism positions A' and B'. The
determined by the speed of the motor 31 driving it. As- undeviated ray again intersects the plane of the disc 13
suming even spacing of :fits, the number of slits 14 in at 0. The direction of rotation of the slit wheel 13 is
the rotating 'wheel 13 and the rotational speed of the 3o assumed to remain the same as in the arrangement shown
wheel determine the frequency of pulsing, in FIG. 2. Thus it is readily possible to alter the value
The image 30 is made up of two parts, one displaced of the time element between the main pulse and the
from the other. The main part 32 is an image of al- auxiliary or synchronizing pulse which precedes or fol-
most the full length of the filament 12 white the dis- lows it.
placed part 33 is somewhat ahead of (that is, it is inter- 35 The time interval between the transmission of the main
cepted first by the approaching slit 14) the main por- beam and' the displaced segment of the ima a will also
tion 32 due to the deviating or refracting action of the depend in a small degree upon the color sensitivity of
prism 20. the photocell used due to dispersion by the prism of
The function of the weak glass prism 20 is illustrated the colors present in radiation from incandescent tung-
in the diagram of FIG. 3. Prism 20 is introduced be- 40 sten. A blue sensitive photocell will give a siiahtly
tween the lens system 11 and the slit wheel 13 in such greater time interval over that given by a red =ersauve
a manner as to intercept only the end portion of the cell. The length of the short spectrum formed by a
rays entering into the formation of the filament image thin crown glass prism will be only ?!ran of the shift of
30 in the plane of the slit .wheel 13 to consequently the image segment caused by its deviation. Since the
displace a portion of this image laterally by reason of 45 amount of displacement can be readily changed by suit-
the refractive or deviating power of the prism 20. The ably positioning the prism relative to the rotating disc,
amount of shift or deviation introduced can be expressed any desired time interval can be secured with photo-
in terms of angle as approximately half of the inter- cells having any of the usual types of color sensitivity.
facial angle of the prism. A 10-degree prism will there- The main ray passing through the slot 14 can be passed
fore deviate a ray by approximately 5 degrees, always 60 through a filter 40 if it is desired to remove all light
in the direction of the base or thick side of the prism. components except the infra-red. The object locating
It is obvious that the rotating slit 14 will first intercept and distance measuring system of this invention, how-
the displaced segment 33 of the filament image and will ever, can utilize directed light pulses in either the visible
consequently pass light to the right angle reflecting prism or invisible portions of the spectrum, although there are
21 and phototube 22 on. the side of the disc or wheel o5 certain advantages, such as for secrecy, in using only
13 remote from the lamp to Th
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21 is so adjusted as to receive only that light which
enters into the formation of the displaced image. Light
in the undisplaced image 32 passes through the slit 14
at a later time, determined by the rotational speed of 60
the slit and the amount of displacement of the displaced
segment 33 of the image, and is transmitted by the
transmitter projection lens 15 and the mirror 16 to the
target 17, as above described, without passing through
the prism 20.
For a fixed rotational speed of the slit wheel 13, it
is obvious that the length of time by which the photo-
tube response pulse will precede the main target pulse
can be altered by changing the linear distance between
the displaced segment 33 of the filament image 30 and 10
the undisplaced portion 32 thereof, This can be effected
by the choice of prism angle used or by movement of
the prism either toward or away from the slit wheel 13.
The closer the prism 20 is to the slit wheel 13, the
smaller wall be the linear displacement between the un- 75
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The light pulses reflected by the mirror 16 are di-
rected toward the target 17 which preferably comprises
a retrodirective reflector such as the well-known tr;ple
mirror deg the operation of which is disclo~wd in Pat-
ent 084,6, to Fessenden, issued July 5, 1921. the
advantage of the retrodirective reflector is that it ref_ : s
back to the paraboloidal mirror 18 substantially all r:,: ;s,
striking it. When a retrodirective reflector (or a u-
rality of them combined as a.unit) is used, it stands
out distinctly regardless of neighboring objects or back-
ground. While a retradirective reflector of the t; ena-
ploying three reflecting surfaces mutually perpen --c?=-r
to one another is to be preferred, the. system of Fibs. I
is -operative with other forms of targets, either goon re-
fleeting objects or diffusely reflecting objects. , .
The rays reflected- back from the target 17 anti picked
up by the paraboloidal mirror 18 are focussed upon the
photoelectric cathode 41 of the tube 19 which, for ex-
amnte_ ;Q a ninlt;.raoe .-,.:..-multiplier tube.
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7t infra-red radiations are used, this tube is constructed
so that it is sensitive to infra-red. A photomultiplier
system including the power supply therefor is shown in
Patent 2,311,981 issued February 23, 1943 to Farnsworth.
The final anode 42 of the photomultiplier 19 is con-
nected to the input circuit of the amplifier 29 which is
of any suitable form for amplifying frequencies normal-
ly to be expected in signals of the character produced
by the photomultiplier 19. The ungrounded terminal of
the amplifier 29 is connected to one of the deflecting
plates 28 while the other deflecting plate 28 is connected
to the ungrounded terminal of the range unit 27. This
causes the deflecting signal applied to the plate 28 to be
an instantaneous sum or difference of the range mark
pulse produced by the range unit 27 and the video out-
put signal of the amplifier 29. When the oscilloscope
shows a registry of the range mark pulse 70 and the
amplified received echo pulse 71 (as indicated in FIG.
6), a reading of the range unit 27 shows the range to
the target. The sweep voltage to produce the horizontal
deflection of the beam is produced by the sweep voltage
generator 24. In practice, it is desirable to have the syn-
chronizing pulse which actuates the sweep circuit 24
occur slightly ahead of the outgoing light pulse in order
that the initial or transmitted light pulse can be seen
on the cathode ray tube 23 as a "zero distance" mark
72 on the range scale. Some of the light from the main
beam 50 can be deviated to a photocell (not shown) to
produce a,pulse corresponding to the mark 72. It will
be obvious that the various pieces of equipment including
the prisms 20 and 21 and the photoelectric cell 22 co-
operate to produce an electrical pulse which is ahead of
the outgoing pulse represented by the dot-dash line 50
in FIG. 1, and shown as mark 72 on the oscilloscope
screen. For further details on the advantages of and
the method of operation of an "irrad" system, reference
should be made to the above-identified Bruce application,
A modification of the arrangement of Flair, I is shcraan
in FIG. 5 wherein parts or elements having the same
functions as corresponding parts in the arrangement of
FIG. 1 have been given the same reference characters.
FIG. 5 shows only a portion of the complete system, the
rest of the syst=,:xa being like that shown in FIG. 1. The
portion of the system shown in FIG. 5 differs from the
corresponding portion of the arrangement of FIG. I in
,the addition of a second weak prism 60 whose base is
turned through 180 degrees with respect to the base of
the prism 20, a second right angle prism 61 which is
similar to the prism 21, and a photocell 62 which can be
similar to the photocell 22 if desired. By making use
of a plurality of weak prisms, such as prisms 20 and
60, it is possible to secure more than one pulse for syn-
chronizing purposes. In the arrangement of FIG. 5,
the pulse produced by the photocell 22 leads the main
pulse and that produced by the phototube 62 follows the
main pulse. By proper placing of the prisms 20 and 60
there can be two early pulses (prepulses) or two late
pulses (post-pulses) or one early and one late pulse
depending on the orientation of the prism bases. Fur-
thermore, the deviating powers of the weak prisms may
be unequal or equal thus causing unequal or equal time
intervals between the deviated light pulses and the main
pulse.
By means of a proper switching system (not shown
for simplicity in the drawings) the pulse of the tube 22
or that of the tube 62 can be used to initiate the opera-
tion of range unit 27 and synchronize the operation of
the sweep and beam brigatening voltage generator 24.
If desired, the prepulse may be used to actuate the sweep
and beam brightening voltage generator 24 and the post-
pulse may be used to start the operation of the range
unit.
Various modifications can be made in the embodiment
described above without departing,from the spirit of the
invcation, the scope of which is indicated in the claims.
6
What is claimed is:
1. In combination, means for generating a main beam
of light, a movable member positioned in the path of
said beam for periodically transmitting light therefrom
s in pulse form, means for producing from said beam a
smaller light beam which is displaced with respect to
said main beam to such an extent and position that said
movable member periodically transmits the pulse of light
from said smaller beam ahead of each pulse of said main
beam, and means for utilizing said pulses of light from
said smaller beam to control apparatus utilizing said
pulses from said main beam.
2. In combination, means for generating a beam of
light including infra-red and other radiation, a movable
member positioned in the path of said beam for peri-
odically transmitting light therefrom in pulse form, means
for producing from said first beam a smaller beam which
is displaced with respect to said first beam to such an
extent and position that said movable member periodical-
ly transmits a pulse of light from said smaller beam aiaead
of each pulse from said first or main beam, means for
filtering said main beam to pass only infra-red radiations.
smaller beam to control apparatus utilizing said pulses
from said first beam.
3. In combination, means for producing and directing
toward a target electromagnetic pulses falling within
the range of infra-red, visible or ultra-violet wavelength
bands, wave collecting means for receiving echoes or re-
flections from said target, wave sensitive electric means
upon which said echoes or reflections are directed by said
collecting means for producing electric pulses correspond-
ing to said received reflections, means for utilizing said
electric pulses to produce an indication of distance aced
direction of said target, optical means for a
second series of electromagnetic pulses inaivdua>.al ones waf
which are time displaced with respect to those in ttte =>sc
-;
series of electromagnetic wises, means for pm'
from said second series of pulses a ser s of ei Lt ' e
pulses, and means for utilizing said last-n>.entioneca e a;:
the pulses to control said means for utilizing said first
electric pulses.
4. In combination, means for generating a main beam
of light, a rotating disc having a slit therein posiaure i
in the path of said main beam for periodically transmit-
ting light therefrom in pulse form, means for producing
from said beam a smaller light beam which is displaced
with respect to said main beam to such an extent and
the pulse of light from said smaller beam ahead of each
pulse of said main beam, and means for utilizing said
pulses of light from said smaller beam to control appa-
ratus utilizing said pulses from said main beam.
5. The combination of elements of claim 4 in which
said means for producing the smaller beam comprises a
prism mounted in the path of said main beam of light at
the edge thereof and which displaces a small portion of
said main beam so that said small portion passes through
said slit in said disc ahead of the light from said main
6. In combination, a lamp having a linear filament
therein for continuously crnitting light, a ro-Lavzr %
having a slit therein, meats for forming an image cr
filament of said lamp up, ,n the plan of s...dJ d Lc. aa.:_+ a
prism for displacing a portion of &.:::d image wnereby
light from the displaced portion of the ima4 +aaees
through said slit prior to the undisplaced porut : vi 5.t .i
maul .image.
7. In combination, a lamp having a line:-
therein for continuously emitting light, a rotating d :
i.ng a slit therein, means for forming an image
filament of said lamp upon the plane of said di,;:
prism for displacing a portion of said image N
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through said slit behind the undisplaced portion of said
image.
8. In combination, a lamp having a linear filament
therein for continuously emitting light, a rotating disc
having a slit therein, means for forming an image of the
filament of said lamp upon the plane of said disc, and a
prism for displacing a small portion of said image where-
by light from the displaced portion of the image passes
through said slit at a different time than the main portion
of said image.
9. In combination, a lamp having a linear filament
therein for continuously emitting light, a rotating disc
having a slit therein, means for forming an image of the
filament of said lamp upon the plane of said disc, a prism
for displacing a small portion of said image whereby light
from the displaced portion of the image passes through
said slit at a different time than the main portion of said
image, and a photocell for picking up the displaced por-
8
tion of said image after it passes through said slit for pro-
ducing therefrom an electric pulse.
10. In combination, a lamp having a linear filament
therein for continuously emitting light, a rotating disc
having a slit therein, means for forming an image of the
filament of said lamp upon the plane of said disc, a prism
for displacing a small portion of said image whereby light
from the displaced portion of the image passes through
said slit at a different time than the main portion of said
image, and a photocell for picking up the displaced por-
tion of said image after it passes through said slit and
for producing therefrom an electric pulse.
References Cited in the file of this patent
15
UNITED STATES PATENTS
914,282
Ives -------------------- Mar. 2, 1909
2,237,193
Mobsby ---------------- Apr. 1, 1941
e
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