OPTICAL COMMUNICATIONS SYSTEM

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP81-00120R000100060046-1
• Release Decision: RIFPUB
• Original Classification: K
• Document Page Count: 8
• Document Creation Date: December 20, 2016
• Document Release Date: November 6, 2002
• Sequence Number: 46
• Publication Date: November 2, 1965
• Content Type: CONT

/7
Approved For Release 2007/09/21 : CIA-RDP81-0012OR000100060046-1
Nov. 2, 1965
Filed April 18, 1963
I!N. E. THOMAS 3,215,842
OPTICAL C OJ MUNICATIONS SYSTEM
a te. }A EYS
4
Approved For Release 2007/09/21 : CIA-RDP81-0012OR000100060046-1
 Approved For Release 2007/09/21 : CIA-RDP81-0012OR000100060046-1
Nov. 2, 1965
Filed April YB,. 1963
F1 3
N. E THOMAS 3,215,842
OPTICAI. COMMUNICATIO S SYSTLII
FIG. 4
INVENTOR
NUMA E. THOMAS
--
ATTORNEYS
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Nov. 2, 1965 K >- THOMAS 3,215,842
INVENTOR
NUMA E. THOMAS
1/yam
ATTORNEYS
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Let states latent ace Patented Nov. 2, 1965
3.215,&!2
OPTICAL C0M.ICS1CATiONS S1STE}T
Narma E. Thomas, Newport News, Va., :r-s''-nor to the
United States of America as represented b. the Admin-
islrator of the National Aeronautics and Space AdmIn-
is!>;-atiioa
Fled Apr, 18, 1963. See. No. 274,065
11 Claims. (CI. 250-199)
(Grssted under 1itle-35, U.S. Code (1952), see. 266)
The invention described herein may be manufactured
and used by or for the Government of the United States of
America for governmental purposes without the payment
of any royalties thereon or therefor.
This invention relates generally to a communications
device and relates with particularity to a semipassive com-
munications system wherein intelligence is transmitted
from a first site to a second site by means of modulating
a light beam.
In general, communications between two remote sites
is presently carried on by means of voice communication
lhros:gh the use of telephone or radio, or by Morse code
light signals. In each of these systems, various situations
can arise which make use of the system highly disadvan-
tageous or impossible of operating, such for example in
air-to-air emergency communication, when transmittir:g
classified communications, ship-to-ship communications,
and the like. Also, the problems of frequency allocation
in regard to radio broadcasting and the problem of wires
when involved with telephones limit the practical capa-
bility of these s}sterns under certain conditions. In addi-
tion, each of the above known systems for intelligence
communication are subject to being monitored by those
to which the communications is not intended, and may be
jammed or intercepted by undesirable recipients while also
normally requiring considerable setup time and mainte-
nance.
There is, tbus, an urgent need in the art for a reliable
light wave or other simple communications system which
can be operated under adverse conditions by semiskilled
personnel under emergency conditions without the require-
ment_-- of expensive and time-consuming setup and main-
tenance problems.
Light-wave type of communications systems have been
employed before; however, in all known prior art sys-
tems of this type, the capabilities thereof were limited due
to the requirements for power supplies at both the trans-
mitter and receiver of the light beams. Also, alinement
problems between the transmitter and the receiver, in the
presently known acoustical responsive light wave com-
muaicatien devices, are critical for operation thereof.
The present invention combines the advantageous fea-
tures of these known prior art systems while minimizing
the alinement problems therein by employing a unique
passive reflector-modulator which is essentially immune
to alinement problems for operation thereof.
Accordingly, it is an object of the present invention to
provide a new and novel communications system.
Another object of the present invention is to provide
a communications system that cannot be monitored by
anyone to which the message is not intended.
Stilt another object of the instant invention is the pro-
vision of a communications system operable by a novice
under emer?ert:y conditions.
A further object of this 'Invention is to provide a corn-
munications system that requires no frequency alloca-
tion.
A still further object of the present invention is the
provision of a semipassive communications device de-
pendent. upon light wave modulation.
2
An additional object of the present invention is the pro-
vision of a novel mechanism for modulating a light beam.
A still further additional object of the present inven-
tion is a new and novel device for the transmission of
intelligence by modulation of a beam of light.
Another object of the present invention is to provide a
long-lived passive modulator device requiring no setup
time or maintenance for use ;n an optical communication
system.
In accordance with the preterit invention, the foregoing
and other objects are attained by providing a lens with a
source of illumination at its focus for projecting a beam
of light, a retrodirectional reflector for modulating and
returning the beam parallel to itself and a larger collecting
lens for collecting and concentrating the return beam aid
focusing it on a photodetector. The projection and c l-
lecting optics are built into a suigle unit with a photo-
detector also contained therein and in electrical con9tec-
Lion with an amplifier and suitable utilization mechanism.
The retrodirectional reflector, which is positioned at a
remote site from which intelligence is desired to be ob-
tained is so constructed and arran_ed as to return the
light wave parallel to itself where it is collected by the
cell ectirg optic, at the first site. T'.:e retrodirection l re-
flector, accordi?ig to the present invention, is a pa,si;e
modulator and consis:s of a corner reflector having three
faces, one or more of which is an optically reflective
flexible diaphragm. The important property of this pe-
cul a r corner reflector lies it. its effect on the behavior of
the light beam returned from it.
It is well known that perfect corner reflectors have
rigid orthogonal fa.;es and alwas's send back inci, ent
energy exactly parallel to. the arrisal direction. Thus,
the deformation of any one 'of the reflecting faces of a
corner reflector will effect modtila.ion of the re:i e tt-d
light rays. The optically reflective flexible diaphragm
face or faces of the corner reflector in the present in?: _s-
tion are position ~d s.7 that upon the influence of sound
waves, such fort xample the voice of a speaker directed
against ,he diaphragm? flexing of the diaphragm in pro-
portion to the wound imparted thereto will be experienced
with corresponding modulation of the light beams being
reflected therefrom. This modulated beam is collected
by the collecting optics at the first site and focused onto
a photodetector wherein it is converted into electrical
impulses corresponding to the sound waves imparted to
the diaphragm at the remote site. These electrical im-
pulses are amplified by a conventional amplifier leading
to a suitable utilization output, such for example, a
speaker.
A more complete appreciation of the invention and
many of the attendant advantages thereof will be readily
apparent as the same becomes better understood by ref-
erence to the. following detailed description when con-
sidered in connection with the accompanying drawings
wherein:
FIG. I is a schematic representation of the light source
receiver unit, amplifier and utiliz }ion mechanism con-
structed in accordance with the p:..-ent invention;
FIG. 2 is a schematic representation of the uni;,,;e
corner reflector as enr toyed in the present laver -_ a
and showing the inciJJ nt and reflected light wave
rection;
FIG. 3 is a perspective view of the unique corner
reflector as employed in, the present invention and ilius,-
tratin; ow form of reourt.ing structure therefor.
FIG. 4 is another view of the corner refector ent-
ployed in the present isvcn.tion and iilustratne the rear-
ward exposed side of _hc flexible diaphragm modulating
face of the reflector onto which the intelligence is im-
parted to cause rnodetation of the light beam being re-
flected from the front side: thereof;
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3
FIG. 5 is a schematic representation of how the op-
tical system of the present invention would be operated
over a distance as a voice communication link between
two individuals;
FIG. 6 's a schematic representation of an alternate
embodiment of the light source receiver unit; and
FiG. 7 is a schematic representation of another all. -r-
mite embodiment of the light-source-receiver unit con-
structed in accordance with the present invention.
Referring n,.w to the drawings, and more particularly
to FIG. 1 there is shown a light-source-receiver unit.
ge:,cril y desi2rated by reference numeral 11. Light
source rcccover unit it includes a tubilzr housing 13, ex-
ternally threaded at one end thereof, in threaded con-
nection with an internally tLrvaded flange connector 15.
The other end of flange connector 15 also threadingly
receives a tubular housing 17 with the opposite end of
bous,rg 17 being closed by an interna'ly threaded end
cap 19.
A reduced diameter tubular container 21 is dispcsed
along the longitudinal axis of unit 11 and maintained ad-
jacent the open end of hous:ng 13, by an annular spider
22. A unidirectional light source 23 powered by a bat-
tery or other conventional power supply, not shown, is
suitably maintained within container 21 with an adjust-
able concentrating lens 25 closing one end of container
21 and in such position as to concentrate the light waves
received from light source 23 into a beam. The other
end of container 21 is closed by a rearwardly directed
convex mirror 27. An annular concave collecting mirror
29 is maintained within unit 11 by flange connector 15
and is adapted to rest on the shoulder 31 formed abou_
the interior surface of connector 15. A suitable photo-
detector 33 is maintained within housing 17 adjacent end
cap 19, in conventional manner, and i; In electrical con-
nection with an amplifier 35 through suitable electrical
lead wires 37 and 39 passing through end cap 19. Am-
plifier 35 is in electrical connection with suitable utiliza-
tion mechanism 41, as will be further explained herein-
after.
Referring now to FIG. 3, the reflector-modulator unit,
generally designated by reference numeral 43, consists of
a corner reflector in which two of the three mutually per-
pendicular surfaces of the reflector are conventional rigid
mirrors 45 and 47. The third reflecting surface of re-
flector 43 is an optically reflecting hexible diaphragm 49.
Diaphragm 49 may be constructed of a flexible material,
such for example Dupont's Mylar film, having a reflective
coating of, for example, evaporated aluminum thereon
and prepared in conventional manner. Mylar is a poly-
ester film made from polyethylene terephthalate, the
polymer fo.rred by the condensation reaction between
ethylene glycol and terephthalic acid and is commercially
available in esse,itially any desired thickness. Dia-
phragm 49 has an overall thickness of approximately
0.5 Hill and is stretched and attached by cementing,
clamping or the like to an open frame 50 for position-
ing in unit 43. Other flexible materials having reflective.
surfaces are cbvio isly also within the scope of this ir.-
vention. An elorgated rod 51 may be attached to re-
flector modulator unit 43 to serve as a mounting or
holding stru::,ure for this unit. Any suitable connection,
such for example as bolt 53, FIG. 4, may be employed
to attach rod 51 to snit 43.
To permit easy asscnibly of unit 43, each of reflector
surfaces 4S, 47, and 49 are position_d therein by its own
pair of steel dowel pins extending through the exterior
4
by reference numeral 67, are provided to retain the re-
spective dowel pins in the framework of each of the re-
fiective surfaces. Dowel pins 69. and 70 for surface 45
are illustrated in FIG. 4. Suitable adjusting screws 54,
g 55, and 56 are provided for respective angular adjust
ment of surfaces 45, 47 and 49 about their respective
dov.el pin flex pivots to permit assembly of the surfaces
in mutually perpendicular alinement. This simple ad-
justment for each of the reflective surfaces permits the
io critical alinement of the surfaces and eliminates critical
tolerances in fabrication thereof that would otherwise be
required to achieve a perfect corner reflector. Once
alinement of the surfaces is atta*ned, adjusting screws, 54,
55, and 56 maintain the surfaces in position axainst the
15 slight tension being exerted thereon by the flex pivot
dowel pins.
Operation -
Since it is well known that. perfect corner reflectors,
20 having rigid orthogonal faces, always send back incident
energy exactly parallel to the arrival direction, as schemat-
ically illustrated in FIG. 2, it is readily apparent that
deformation of one of the reflecting faces immediately ef-
fects modulation of returned rays. Since the energy
23 incident of one face must also be ref;ected by the ether
two, it is sufficient to have only one of the reflecting str-
faces made as a flexible diaphragm, as shown, although
it is also within the scope cf this invention to provide
two o- all of the reflective surfaces of flexible diaphragm
30 construction.
Information causing deformation of any or all of the
reflecting faces is carried on the return beam by virtue
of an angular spreading of the returned rays in such
manner that the energy per unit area falling on a receiver
3; varies in accordance with the mod?.ilation impressed on
the flexible face 4) of the comer reflector 43.
In operation, therefore, light from source 23 is con-
centrated and focused by lens 25 into a beacon light in
the general direction of reflector-modulator unit 43 wiich
4n may be positioned at a considerable distance from light-.
source-receiver unit 11. The reflec:or-modulator 43 re-
turns the light beam parallel to itself where it is collected
by the larger optical system, 27 and 29, and focused onto
the photodetector 33. The width of the returned light
45 beam is approximately twice the diameter of the ccrner
reflector plus the diameter of the original light source
wh:ch in the illustrated embodiment can be taken to be
the diameter of the projecting lens and accounts for the
needed larger collecting optics.
50 The optically reflecting diaphragm 49 of corner re-
flector 43 may be modulated either acoustically or elec-
trically. This modulating action produces a focusing ef-
fect and results in the returned light beam being alter-
nately expanded and contracted with a consequent fluc-
53 tuation in intensity at the collecting optics 27 and 29. The
photodetector 33 converts these changes in intensity to
electrical impulses which are amplified by amplifier 35
leading to utilization circuitry 41.
As shown in FIG. 5, a signal, such for example a
C, Li voice sound, when directed onto the rear of flexible face
49 will cause flexing of face 49 in proportion to the sound
imparted thereai-ainst wi:h concurrent modulation of the
reflected light ray directed toward light-source receiver
unit 11. This reflected ray of light, being returned eacen-
65 tially parallel to the light source, is received by annular
collecting mirror 19 and reflected to?vnrd concentrating
mirror 27 ss tete it is reflected onto photodetector 33 and
converted into electrical signals. These signals are then
live reflective surface along one side thcrof. The ends transmitted to amplifier 35 and utilization circuit 41 and
of dowel pins 59 and 61 for surface 49 are shown in ,o transcribed as the signal or voice originally imparted to
FIG. 4 extending through open framework 50. A pair diaphragm 49.
of set screws 63 and 64 are provided perpendicular In the illustration shown in FIG. 5. this utilization
Through one surface of the exterior wall of unit 43 to mechanism 41 is in the form of ear phones 57 although
secure dowel pins 59 and 61 in position. Similar set it is apparent that any other conventional type of utiliea-
4cre ti; one. of which is shown in FIG. 3 and designated 75. lion mechanism may be orcployed within the scope of thi,
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invention. Thu---, as schematically illustrated in FIG. 5,
a steady beam of light from a distant source mn be mod-
ulated and sent back to the source by passive corner
reflector-modulator unit 43 which requires no power other
than that supplied by the voice of the speaker acting
directly upon the flexible face 49 of modulator unit 43
(FIG. 4).
A wort ing model of the presently descry-bed invention
has been constructed which utilizes a battery powered 25-
watt zirconium concentrated arc lamp light source. The
modulator-reflector 43 in this experimental model was
fabricated using two rigid mirrors and one stretched dia-
p'lraga of 0.5 mil aluminized Mylar fii_n. This strecheta
diaphragm was cemented to open f: p mework 50 by a con-
ventional adhesive. Framework 50 is designed to facili-
tate assembly and adjustment thereof by adjusting screws
55 within corner reflector unit 43, as pointed out herein-
befotx-
W t.h this rudimentary model, clear audible tronsmis-
sions of voice and musical content have been made over
a distance exceeding one-half mile in bright sunlight.
With higher power light source and refined design in both
the light-source-receiver unit 11 and the reflector-modu-
lator unit 43, there appears to be no practical limit to the
comet -rications range permissible when employing the
teachiaes of the present invention.
1.:ferring now to FIG. 6, a schematic representation
of an alternate embodiment of the light-source-receiver
unit 111 is shown and includes a tubular housing 117
closed at one end by an end cap 119. A reduced diam-
eter tubular housing 121 is disposed along the longitudinal
axis of omit Ill. and maintained adjacent the open end of
housi .g 117 by suitable structure, not shown. A uni-
directional light source 123 is maintained within housing
121 in a suitable manner with an adjustable concentrating
lens 323 closing the open end of housing 121 in such posi-
tion as to concentrate the light waves received from light
source 123 into a beam. In this embodiment the receiv-
ing o;ties for the reflected beam consists of plano-concave
mirror 129 xhich directs the reflected light waves directly
ratio photodetector 133. The remaining operation of this
embodiment is the same as that described hereinbefore in
reference to FIG. I with photodetector 133 being in.elec-
trical connection with suitable amplifier and utilization
mechanism, not shown.
A further modification illustrated in FIG. 7 shows the
light-source-receiver unit 211 including a frusto-conical
housing 217. A tubular housing 221 of smaller diameter
than the base of conical housing 217 houses light source
223 with concentrating lens 225 being provided therein
f x f cesing the light from source 223. In this embodi-
ment, the hereinbefore described conrtve lens is replaced
by the annular refractory lens 228 which is positioned
within the open base end of conical housing 217 and
around tubular housing 221. Refractory lens 228 serves
as connecting structure for the two housings while also
serving to receive the reflected light waves and direct
them onto photodetector 233. The remaining operation
of this embodiment is the same as that described herein-
before in reference to FIG. I with photodetcctcr 233 be-
ing in electrical connection with suitable amplifier and
utilization circuitry, not shown.
Although only selective embodiments of the present in-
vention have been specifically described, it is readily
apparent to those skilled in the art that the { ring m.le de-
scribed herein is equally applicable to intclligan com-
munization by microwave,. visible light, infrared, and
untraviotet frequencies, to mention but a few possibilities.
It is also anticipated that the present invention will
find utility in providing a voi e: ces-aaunicat`.~ns system
for use in manned flight reentry where preset:-day com-
munications systems tend to undergo blackout conditions
uri3r~ various phases of the reentry t-ajectory. When
o:rtilir_ing the present invention under these conditions, a
laser could be employed for the source of light and the
0
lightweight passive reflector-modulator unit 43 would be
positioned in the reentering body in position to be influ-
enced by voice sounds emanating from the occupant of the
reentry vehicle.' The possibility of other uses, such for ex-
ample in ship-to-ship communications, surveying team
communications, Forme and intelligence work, and forest-
fire control are readily apparent to those skillea in the art.
also, during air-sea rescue operations, the passive modu-
lator unit 43 could be packed in survival gear or air-
10 stropped to the stranded operator to facilitate rescue
operations.
Because the returned beam according to the present
invention is always parallel to the incident beam, except
for the fluctuations in spread caused by the modulation,
13 and because there is no information on the incident beam,
the information-carrying returned beam can only be in-
tercepted by looking directly along the return signal path
toward the modulator 43. The system is therefore line-
cf-sight in character and the presence of an object inter-
20 posed in the communications beam of suffrc;cnt size to
interrupt or block off the incident beam from the modu-
L-tor will obviously stop communications, however, the
;resence of small particles in the incident beam path, such
as fog, dust, and the like will not cause'system failure
25 until the roundtrip energy falls below the receiver capa-
bilities.
This system is therefore jamproof, that is, it cannot be
jammed by signal generation. The system also cannot be
monitored since the modulated energy is absorbed at the
30 icht-source-receiver unit. The oper aticn of this system
requires no frequency allocation, and the reflector-modula-
tor can be operated under emergency conditions by a
novice in that it requires no setup time or maintenance
ce it is a long-lived passive unit. Two-way commu-
3:, s:catien could obviously be achieved within the scope of
This invention by simply mounting a passive modulator
on each source-receiver unit.
Due to the unique features of corner reflectors, thin
_ysstem is relatively insensitive to orientation of the pas-
40 sive modulator 43 and acquisition and pointing of the
units are not critical to the operation of the device.
Thus, the light-source-re -eiver unit 11, first with a broad-
en c, beam of light from source 23, may be aimed in the
eerara; direction of the modulator-receiver unit 43 and
:ben communication is established, the light-source-re-
43 ceiver beam is reduced in spread and corrected in orien-
tation to achieve a more intense signal by conventional
means.
It is the unique optical characteristics of the corner re-
f+_ctor that alleviate the pointing problems of the system
50 and also contributes to a system which has relatively low
energy loss with distance. It is for the latter reasons that
extremely long ranges are possible when utilizing the pres-
ent invention for extreme distance communication.
Since it has already been determined that light rays can
55 be bounced off the Moon's surface, it is anticipated that
by using a high-po?./ered light source, such for example
a laser and by providing an astronaut explorer on the
Moon's surface with the lightweight passive reflector, voice
communication between the Earth an] the Moon could
tot} be maintained by utilizing the present invention.
Obviously, many modifications and variations of the
present invention are possible in toe light of the above
teachings, For example, although the surfaces of reflec-
tor unit 43 are illustrated in the form of sectors, corner
t'a reflectors constructed of square or rectangular ret'.Actir z
surfaces are ohvicu !v also within rho cope of this
tian. It is therefc e to be u; ?ors-, - 'd that within the
scope of tl-t appended claims, the invention may be prac-
ticed than as specifcYy described herein.
i0 What is .claimed not dYs;r~ 7 to be secured by Letters
Patent of the United States is:
1. Apparatus for tray,mitting a signal between two
sites comprising: a first unit at one site housing a lens
and a source of light inas.tion to be focused into a beam
45 by said:lens, a secorrt unit at a remote. site, said second
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3,211,,5t
7
unit including a muNisurface ell-ctor for returning the
beam pars lel to ;vtcif, at least one reflective surface of
said reflector comprising an acoustically rr_p-)nsive dia-
phragm for modulating rid lr:am, s: id fir urir also con-
taining optical means for collecting d fo,un~ng the re- 5
turned beam, a photodetector for receiving and convert-
ing ch..nges in beam intensity,, of the returned beam as a
result of acoustical modulation by said di:phragm into
electrical impulses, means for an-plify ing said electrical
impulses, and utilization moans for consc rting the am- 10
plified impulses into .le acoust;cN imparted to said dia-
phragm at said remote site.
2. Apparatus for transmitting intelligence between two
sites, comprising: a first unit at cne site and a second unit
at a remote site, said first unit including a s!=ce of light 15
and a lens for focusing sad lieltt into a beam, said second
unit including a passive r;uitisurface reflector constructed
and arranged so as to rcce7.ve and return the beam of light
from said first unit substantially paraI.cl to itself, said
reflector including acoustically vibratile mean-, for modu- 20
lation of said beans of light by acoustics imparted thereto
at said remote site to vary the intensity of the reflected
beam, said first unit further including means for receiving
and converting changes in the reflected beam intensity
into detectable electrical impulses. 25
3. Apparatus for transmitting intelligence between two
sites, comprising: a first unit at one site and a second unit
at a remote site, said first unit including a cousin?, a
source of light within said housing, a lens within sai f hous-
ing for focusing said light into a beam, sal' second unit 30
including a passive multisurface reflector constr, ted and
arranged so as to receive and return the beam of light
from said first unit parallel to itself, said rel.e,.tor includ-
ing intelligence responsive means for rna-ulation of said
beam of light in response to and inpropo-':on to scousti- 33
cal signals imparted thereagainst at said remove site to
vary the intensity of the reflected beam, said first unit
further inclt:di!ig a photodetector for receiving and con-
verting changes in the reflected beam intensity into elec-
trical impulses, and means for amplifying and utiliL.ing 10
the impulses.
4. Apparatus according to claim 3 including optical
means at said first site for concentrating the reflected
beam of light prior to receipt thereof by said photode-
tector.
5. Apparatus according to claim 4 wherein said optical 45
means includes an annular concave mirror and a convex
lens in optical alinement therewith.
6. A reflector for returning a beam of light parallel to
a light source comprising: three mutually perpendicular.
reflective surfaces in intimate contact, at least one of said 50
reflective surfaces comprising a rigid open framed. ork
having a flexible diaphragm spanning the opening and
fixedly secured along the periphery thereof, said flexible
diaphragm being provided with an exposed reflective sur-
face said flexible diaphragm being a plastics film and 53
having an aluminum coating thereon constituting said
reflecting surface, said fixed periphery of said flexible
diaphragm being maintained in mutual perpendicular
alinement with the remaining reflective surfaces while
the reflective surface area circumscribed by ire fixed pe- CO
riphery is so constructed and arranged a- to be signal-
responsive flexibly vibratile to eff. ct detectable modula-
tion of a reflected light beam.
7. A system for providing a coin murication link be-
tween two distant sites, comprising: t;fs
means at a first site for projecting a be --Ti of light to-
ward a remote second site,
means at said remove second site `c reflecting the
light waves of said beam of lib' f sts rt n aiiy par-
allel to itself, 70
said mean's at said remote site effecting modulation of
light waves reflected therefrom as a rep+tlt of acousti-
cal intelligence imparted thereto at said remote site,
rrteans:at the first site for collecting ..:.d focusing the
relec.ted modulated light waves, 75
means for converting the reflected modulated light
waves into electrical impulses,
means for amplifying said electrical impulses,
means for consorting and transcribing the amplified
electrical impulses into the acoustical intelligence
emanatin3 from said second site, said means at said
remote second site including:
a passive corner reflector,
said corner 'L'ector having two rigid faces and one
flexible orthogonal fax,
each of said rgid faces and said flexible face having
an exposed reflective surface and a surface secured
to its individual frame,
each said individual frame berg positioned within a
a plurality of dowel pins extending through said corner
housing and received by portions of each individual
frame,
means on said corner housing for locking said dowel
pins in position,
means on each individual frame for securing said dowel
pins therein,
said dowel pins being constructed and arranged so as
to constitute flex pivots for each said individual
frame,
and means for angularly adjusting said individual frames
within said corner housing to accurately aline said
individual faces therein.
S. A system for providing a communication link be-
tween two distant sites, comprising:
means at a first site for projecting a beam of light
!oward a remote second site,
means at said remote second site for reflecting the
light waves of said beam of light substantially
parallel to itself,
said means at said remote site effecting modulation of
Ii ;ht waves reflected therefrom as a recast of acousti-
cal intelligence imparted thereto at sci:l remote site.
means at the first site for collecting and focusing the
reflected modulated light waves,
means for converting the reflected modulated light
waves into electrical impulses,
means for amplifying said electrical impulses,
means for converting and transcribing the amplified
electrical impulses into the acoustical inteiagence
emanating from said second site,
said means at said first site for collecting and focusing
the reflected modulated light waves includes:
an annular concave mirror in axial alinement with
said means for projecting the beam of light; and,
a convex collimating lens.
9. A system as in claim 8 wherein said means at said
first site for collecting and focusing the reflected modu-
lated light waves is a concave mirror and said means for
converting the reflected modulated light waves into elec-
trical impulses is a photodetector, said photodetector
being housed between said concave mirror and said
means at said first site for projecting a beam of light.
10. A system as in claim 8 wherein said means at
said first site for collecting and focusing the reflected
modulated light waves is an annular refractory lens, said
annular refactory lens being housed in circumferential
relationship to said means for p ejecting a beam of lit; st.
11. A passive reflector for urning el
waves alc-g a parallel path from a rernc'
netic energy source, comprising:
r corner re.lector having open corner ho+using,
said comer reflector including two rigid and one flexible
face,
each said rigid face and said flexible face being se-
cured -0 its in vidual open framework.
saict flexit ie face beir.g so cons:ru?ted and arranged as
to flexibily vibrate in response to acoustical si-,iials
impart-d the,z *:.inct and thereby modulate reflected
incident el+:ctrernagnetic waves in proportion to the
at oust.cal siga4,
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 Approved For Release 2007/09/21 CIA-RDP81-0012OR000100060046-1
9
means for securing each said individual framework
within said open corner horsin&
means for individually angularly aJjusting each of said
facts within said corner housing to attain alinement
thereof, said means for se:uring said inc.i%ideal
framework within said open carncr housin__g_ in,:luding.
a plurality of dowel pins cxten.lir)g throw 7h said corner
housing and received by portions of each individual
frame.
said dowel pins being so ccnstructed and arranged as
to form flcx pivots for each individual fr,.mework.
a plurality cf set strews equal in number to said dowel
pins extending through said corner housing for in-
dividually liking said dowel pins in position therein,
and means extending throt?gh said open corner hous-
ing to enga.-c each said frammework for effecting
angular adjustment thereof.
10
Referen"s Cited by the Examlae
UNITED STATES PATENTS
1,384.013
7/21
Fessenden.
2 :5,445
3/44
Atwood ------- ------ 250--199
2,332,984
12/47
Ilufonbom ------------ 343-18
2,4f6,OOO
4/49
Bra .n -------------- 250-i99
2.543.130
7/51
Rat,crt%on --------- _-- 343-18
2.885,673
5/59
Pratt et al. ----- --->- 343-18
2,953.059
9/60
Rt.dm.tn et al.
3,04-,860
7/62
Swallow et al. ---------- 343-18
3,065,352
11/62
McFarlane ----- >----- 250-199
FORFiCN PATENTS
21,856
10/03
Great Britain.
317,318
5/30
Great Britain.
6
Approved For Release 2007/09/21 : CIA-RDP81-0012OR000100060046-1