`
`
`
`EXHIBIT
`
`EXHIBIT
`1004
`
`1004
`
`

`

`Nov. 2, 1965
`
`N. E. THOMAS
`
`3,215,842
`
`OPTICAL COMMUNI CATIONS SYSTEM
`
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`Panasonic Corporation
`
`Exhibit 1004
`
`
`
`
`

`

`Nov. 2, 1965
`
`N. E. THOMAS
`OPTICAL COMMUNI CATIONS SYSTEM
`
`3,215,842
`
`Filed April 18, 1963
`
`3 Sheets-Sheet 2
`
`
`
`INVENTOR
`NUMA E. THOMAS
`
`BY
`
`JAM/é,
`
`ATTORNEYS
`
`

`

`Nov. 2, 1965
`
`N. E. THOMAS
`
`3,215,842
`
`OPTICAL COMMUNICATIONS SYSTEM
`
`Filed April 18, 1963
`
`3 Sheets-Sheet 3
`
`
`FIG.5
`
`INVENTOR
`NUMA E. THOMAS
`
`BY
`
`wjfl&/Zg
`W/ ATTORNEYS
`
`

`

`3,215,842
`Patented Nov. 2, I965
`
`United States Patent Office
`
` 1
`
`2
`
`3,215,842
`OPTICAL COMMUNICATIONS SYSTEM
`Numa E. Thomas, Newport News, Va., assignor to the
`United States of America as represented by the Admin-
`istrator of the National Aeronautics and Space Admin-
`istration
`Filed Apr. 18, 1963, Ser. No. 274,065
`11 Claims.
`(Cl. 250—199)
`(Granted under Title 35, U.S. Code (1952), sec. 266)
`
`5
`
`10
`
`15
`
`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 20
`is presently carried on by means of voice communication
`through 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 transmitting
`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 systems 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.
`
`25
`
`30
`
`35
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`45
`
`50
`
`55
`
`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 in an optical communication
`system.
`In accordance with the present 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 and
`focusing it on a photodetector. The projection and col-
`lecting optics are built into a single unit with a photo-
`detector also contained therein and in electrical connec-
`tion 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 arranged as to return the
`light wave parallel to itself where it is collected by the
`collecting optics at the first site. The retrodirectional re-
`flector, according to the present invention,
`is a passive
`modulator and consists of a corner reflector having three
`faces, one or more of which is an optically reflective
`flexible diaphragm. The important property of this pe-
`culiar corner reflector lies in its effect on the behavior of
`the light beam. returned from it.
`It is well known that perfect corner reflectors have
`rigid orthogonal faces and always send back incident
`energy exactly parallel to the arrival direction. Thus,
`the deformation of any one of the reflecting faces of a
`corner reflector will effect modulation of the reflected
`light rays. The optically reflective flexible diaphragm
`face or faces of the corner reflector in the present inven-
`tion are positioned so that upon the influence of sound
`waves, such for example the voice of a speaker directed
`against the diaphragm, flexing of the diaphragm in pro-
`portion to the sound 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:
`
`There is, thus, 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 40
`personnel under emergency conditions without the require—
`ments 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-
`munication 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.
`Still another object of the instant invention is the pro-
`vision of a communications system operable by a novice
`under emergency conditions.
`A further object of this invention is to provide a com-
`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.
`
`60
`
`65
`
`FIG. 1 is a schematic representation of the light source
`receiver unit, amplifier and utilization mechanism con-
`structed in accordance with the present
`invention;
`FIG. 2 is a schematic representation of the unique
`corner reflector as employed in the present
`invention
`and showing the incident and reflected light wave di-
`rection;
`FIG. 3 is a perspective View of the unique corner
`reflector as employed in the present invention and illus-
`trating one form of mounting structure therefor;
`FIG. 4 is another View of the corner reflector em-
`ployed in the present invention and illustrating the rear—
`ward exposed side of the flexible diaphragm modulating
`0 face of the reflector onto which the intelligence is im-
`parted to cause modulation of the light beam being re-
`flected from the front side thereof;
`'
`
`

`

`3,215,842
`
`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 is a schematic representation of an alternate
`embodiment of the light source receiver unit; and
`FIG. 7 is a schematic representation of another alter-
`nate embodiment of the light-source—receiver unit con-
`structed in accordance with the present invention.
`Referring now to the drawings, and more particularly
`to FIG.
`1
`there is showu a light-source-receivcr unit,
`generally designated by reference numeral 11. Light
`source receiver unit 11 includes a tubular housing 13, ex-
`ternally threaded at one end thereof,
`in threaded con-
`nection with an internally threaded flange connector 15.
`The other end of flange connector 15 also threadingly
`receives a tubular housing 17 with the opposite end of
`housing 17 being closed by an internally threaded end
`cap 19.
`A reduced diameter tubular container 21 is disposed
`along the longitudinal axis of unit 11 and maintained ad-
`jacent the open end of housing 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 rearward'ly 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 about
`the interior surface of connector 15. A suitable photo-
`detector 33 is maintained within housing 17 adjacent end
`cap 19, in conventional manner, and is 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 flexible 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 formed by the condensation reaction between
`ethylene glycol and terephthalic acid and is commercially
`available in essentially any desired thickness. Dia-
`phragm 49 has an overall
`thickneSS of approximately
`0.5 mil 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 obviously also Within the scope of this in-
`vention. An elongated rod 51 may be attached to re-
`flector modulator unit 43 to serve as a mounting or
`holding structure for this unit. Any suitable connection,
`such for example as bolt 53, FIG. 4, may be employed
`to attach rod 51 to unit 43.
`To permit easy assembly of unit 43, each of reflector
`surfaces 45, 47, and 49 are positioned therein by its own
`pair of steel dowel pins extending through the exterior
`wall of unit 43 into the open framework of the respec-
`tive reflective surface along one side therof. The ends
`of dowel pins 59 and 61 for surface 49 are shown in
`FIG. 4 extending through open framework 50. A pair
`of set screws 63 and 64 are provided perpendicular
`through one surface of the exterior wall of unit 43 to
`secure dowel pins 59 and 61 in position.
`Similar set
`screws, one of which is shown in FIG. 3 and designated
`
`0‘!
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`10
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`20
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`4:0
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`45
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`50
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`55
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`65
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`70
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`4
`by reference numeral 67, are provided to retain the re-
`spective dowel pins in the framework of each of the re-
`flective surfaces. Dowel pins 69 and 70 for surface 45
`are illustrated in FIG. 4. Suitable adjusting screws 54,
`55, and 56 are provided for respective angular adjustj
`ment of surfaces 45, 47 and 49 about their respective
`dowel 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
`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 attained, adjusting screws, 54,
`55, and 56 maintain the surfaces in position against the
`slight
`tension being exerted thereon by the flex pivot
`dowel pins.
`
`Operation
`
`Since it is well known that perfect corner reflectors,
`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
`incident of one face must also be reflected by the other
`two, it is sufficient to have only one of the reflecting sur-
`faces made as a flexible diaphragm, as shown, although
`it is also within the scope of this invention to provide
`two or all of the reflective surfaces of flexible diaphragm
`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
`varies in accordance with the modulation impressed on
`the flexible face 49 of the corner 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 which
`may be positioned at a considerable distance from light-
`source-receiver unit 11. The reflector-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
`beam is approximately twice the diameter of the corner
`reflector plus the diameter of the original light source
`which in the illustrated embodiment can be taken to be
`the diameter of the projecting lens and accounts for the
`needed larger collecting optics.
`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-
`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.
`7
`As shown in FIG. 5, a signal, such for example a
`voice sound, when directed onto the rear of flexible face
`49 will cause flexing of face 49 in proportion to the sound
`imparted thereagainst with concurrent modulation of the
`reflected light ray directed toward light-source receiver
`unit 11. This reflected ray of light, being returned essen-
`tially parallel to the light source, is received by annular
`collecting mirror 29 and reflected toward concentrating
`mirror 27 where it is reflected onto photodetector 33 and
`converted into electrical signals. These signals are then
`transmitted to amplifier 35 and utilization circuit 41 and
`transcribed as the signal or voice originally imparted to
`diaphragm 49.
`this utilization
`In the illustration shown in FIG. 5,
`mechanism 41 is in the form of ear phones 57 although
`it is apparent that any other conventional type of utiliza~
`tion mechanism may be employed within the scope of this
`
`
`
`

`

`3,215,842
`
`5
`invention. Thus, as schematically illustrated in FIG. 5,
`a steady beam of light from a distant source can 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 working model of the presently described 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-
`phragm of 0.5 mil aluminized Mylar film. This stretched
`diaphragm was cemented to open framework 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—
`before.
`With this rudimentary model, clear audible transmis-
`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
`communications range permissible when employing the
`teachings of the present invention.
`Referring 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 unit 111 and maintained adjacent the open end of
`housing 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 125 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 optics for the reflected beam consists of plane-concave
`mirror 129 which directs the reflected light waves directly
`onto photodetector 133. The remaining operation of this
`embodiment is the same as that described hereinbefore in
`reference to FIG. 1 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
`for focusing the light from source 223.
`In this embodi-
`ment, the hereinbefore described concave 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. 1 with photodetector 233 be-
`ing in electrical connection with suitable amplifier and
`utilization circuitry, not shown.
`Although only selective embodiments of the present in-
`vvention have been specifically described,
`it
`is readily
`apparent to those skilled in the art that the principle de-
`scribed herein is equally applicable to intelligence com-
`munication by microwave, visible light,
`infrared, and
`untraviolet frequencies, to mention but a few possibilities.
`It is also anticipated that the present invention will
`find utility in providing a voice communications system
`for use in manned flight reentry where present-day com-
`munications systems tend to undergo blackout conditions
`during various phases of the reentry trajectory. When
`utilizing the present invention under these conditions, a
`laser could be employed for the source of light and the
`
`C7!
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`6
`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, police and intelligence work, and forest-
`fire control are readily apparent to those skilled in the art.
`Also, during air-sea rescue operations, the passive modu-
`lator unit 43 could be packed in survival gear or air-
`dropped 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,
`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-
`of—sight in character and the presence of an object inter—
`posed in the communications beam of sufl‘icient size to
`interrupt or block off the incident beam from the modu-
`lator will obviously stop communications. However, the
`presence of small particles in the incident beam path, such
`as fog, dust, and the like will not cause system failure
`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
`light-source-receiver unit. The operation 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
`since it is a long-lived passive unit. Two-way commu-
`nication 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, this
`system is relatively insensitive to orientation of the pas-
`sive modulator 43 and acquisition and pointing of the
`two units are not critical to the operation of the device.
`Thus, the light—source-receiver unit 11, first with a broad—
`ened beam of light from source 23, may be aimed in the
`general direction of the modulator-receiver unit 43 and
`when communication is established,
`the light-source-re-
`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-
`flector that alleviate the pointing problems of the system
`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
`be bounced off the Moon’s surface, it is anticipated that
`by using a high—powered 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 and the Moon could
`be maintained by utilizing the present invention.
`Obviously, many modifications and variations of the
`present invention are possible in the light of the above
`teachings. For example, although the surfaces of reflec-
`tor unit 43 are illustrated in the form of sectors, corner
`reflectors constructed of square or rectangular reflecting
`surfaces are obviously also within the scope of this inven-
`tion.
`It is therefore to be understood that within the
`scope of the appended claims, the invention may be prac-
`ticed otherwise than as specifically described herein.
`What is claimed and desired to be secured by Letters
`Patent of the United States is:
`1. Apparatus for transmitting a signal between two
`sites comprising: a first unit at one site housing a lens
`and a source of light in position to be focused into a beam
`by said lens, a second unit at a remote site, said second
`
`

`

`3,215,842
`
`7
`unit including a multisurface reflector for returning the
`beam parallel to itself, at least one reflective surface of
`said reflector comprising an acoustically responsive dia-
`phragm for modulating said beam, said first unit also con—
`taining optical means for collecting and focusing the re—
`turned beam, at photodetector for receiving and convert-
`ing changes in beam intensity of the returned beam as a
`result of acoustical modulation by said diaphragm into
`electrical impulses, means for amplifying said electrical
`impulses, and utilization means for converting the am-
`plified impulses into the acoustics imparted to said dia-
`phragm at said remote site.
`2. 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 source of light
`and a lens for focusing said light into a beam, said second
`unit including a passive multisurface reflector constructed
`and arranged so as to receive and return the beam of light
`from said first unit substantially parallel to itself, said
`reflector including acoustically Vibratile means for modu‘
`lation of said beam 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.
`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 housing, a
`source of light within said housing, a lens within said hous-
`ing for focusing said light into a beam, said second unit
`including a passive multisurface reflector constructed and
`arranged so as to receive and return the beam of light
`from said first unit parallel to itself, said reflector includ-
`ing intelligence responsive means for modulation of said
`beam of light in response to and in proportion to acousti—
`cal signals imparted thereagainst at said remote site to
`vary the intensity of the reflected beam, said first unit
`further including a photodetector for receiving and con-
`verting changes in the reflected beam intensity into elec-
`trical impulses, and means for amplifying and utilizing
`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
`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
`reflective surfaces comprising a rigid open framework
`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
`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 the fixed pe-
`riphery is so constructed and arranged as to be signal-
`responsive flexibly Vibratile to effect detectable modula-
`tion of a reflected light beam.
`7. A system for providing a communication link be-
`tween two distant sites, comprising:
`means at a first site for projecting a beam of light to~
`ward a remote second site,
`means at said remote second site for reflecting the
`light waves of said beam of light substantially par-
`allel to itself,
`said means at said remote site effecting modulation of
`light waves reflected therefrom as a result of acousti-
`cal intelligence imparted thereto at said remote site,
`means at the first site for collecting and focusing the
`reflected modulated light waves,
`
`Cl
`
`10
`
`15
`
`20
`
`25
`
`30
`
`4:0
`
`60
`
`7O
`
`8
`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
`intelligence
`emanating from said second site, said means at said
`remote second site including:
`a passive corner reflector,
`said corner reflector having two rigid faces and one
`flexible orthogonal face,
`each of said rigid faces and said flexible face having
`an exposed reflective surface and a surface secured
`to its individual frame,
`each said individual frame being positioned within a
`corner housing,
`a plurality of dowel pins extending through said corner
`housing and received by portions of each individual
`frame,
`1
`means on said corner housing for lockingsaid 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.
`8. A system for providing a communication link be-
`tween two distant sites, comprising:
`means at a first site for projecting a beam of light
`toward 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
`light waves reflected therefrom as a result of acousti-
`cal intelligence imparted thereto at said 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
`intelligence
`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 projecting a beam of light. 7
`11. A passive reflector for returning electromagnetic
`waves along a parallel path from a remote electromag-
`netic energy source, comprising:
`a corner reflector having an open corner housing,
`said corner reflector including two rigid and one flexible
`face,
`each said rigid face and said flexible face being se-
`cured to its individual open framework,
`said flexible face being so constructed and arranged as
`to flexibily vibrate in response to acoustical signals
`imparted thereagainst and thereby modulate reflected
`incident electromagnetic waves in proportion to the
`acoustical signal,
`
`
`
`

`

`3,215,842
`
`9
`means for securing each said individual framework
`within said open corner housing,
`means for individually angularly adjusting each of said
`faces within said corner housing to attain alinement
`thereof,
`said means
`for securing said individual
`framework within said open corner housing including,
`a plurality of dowel pins extending through said corner
`housing and received by portions of each individual
`frame,
`said dowel pins being so constructed and arranged as
`to form flex pivots for each individual framework,
`a plurality of set screws equal in number to said dowel
`pins extending through said corner housing for in-
`dividually locking said dowel pins in position therein,
`and means extending through said open corner hous-
`ing to engage each said framework for efiectiug
`[angular adjustment thereof.
`
`10
`References Cited by the Examiner
`UNITED STATES PATENTS
`7/21
`Fessenden.
`3/44
`Atwood ______