Covert selective acquisition device for identifying friend or foe

• US 5,870,215 A
• Filed: 12/22/1995
• Issued: 02/09/1999
• Est. Priority Date: 12/22/1995
• Status: Expired due to Fees

• Current Assignee: Northrop Grumman Corporation
• Original Assignee: Northrop Grumman Corporation
• Inventors: Milano, Steven J., Herzel, James S.
• Primary Examiner(s): BACARES, RAFAEL D
• Application Number:
  US08/577,990
• Time in Patent Office: 1,145 Days
• Field of Search: 359/152, 359/159, 359/172, 359/169, 359/170, 359/155, 342/45
• US Class Current: 398/108
• CPC Class Codes: H04B 10/11 Arrangements specific to free-space transmission, i.e. transmission through air or vacuum

Abstract

A compact infrared identification and communication assembly, including a transponder device and at least one interrogator device, is provided. Each device includes a housing having an opening therein through which light may be received or emitted. The opening has a spectral filter mounted therein which permits only a specific frequency band of incident light to pass into and out from the housing. A dichroic beam splitter is mounted in the housing, aligned with the spectral filter, for reflecting and transmitting separate selected portions of the specific frequency band. A photodiode is aligned with the beam splitter, thereby receiving light from one of the separate portions, for example the transmitted portion. The photodiode converts its received light into an electrical signal which is subsequently converted into a form which a user may easily understand, for example an LED display. The devices further include a light emitting diode, which is also aligned with said dichroic beam splitter, for converting a second electrical signal, produced by a user into an emitted light signal. The emitted light signal is of the other separate portion, for example the reflected range.

Claims

1. An infrared identification and communication assembly, including at least two devices, each of which comprises:

a housing having a light receiving opening therein;

a spectral filter, mounted within said light receiving opening, which permits a frequency bandwidth of incident light to enter into and exit from said housing, said bandwidth including first and second frequencies, wherein one of said first and second frequencies comprises a transmitted frequency and the other of the first and second frequencies comprises a received frequency;

a dichroic beam splitter, mounted in optical receiving alignment with said spectral filter, for reflecting and passing therethrough selected portions of said frequency bandwidth, wherein said selected portions which are reflected include one of said first and second frequencies, and said selected portions which pass therethrough include the other of the first and second frequencies;

a photodiode, mounted in optical receiving alignment with said dichroic beam splitter, for receiving said received frequency, and converting same into a first electrical signal;

a solar noise rejection circuit, through which circuit the first electrical signal is directed, which includes a pair of amplifiers coupled via a feedback loop whereby constant level solar noise components of the first electrical signal are subtracted therefrom;

means by which a user may produce a second electrical signal; and

a light emitting diode, aligned in light transmitting alignment with said dichroic beam splitter, for converting said second electrical signal into a light signal comprising the transmitted frequency, and emitting said light signal through said spectral filter and out of said housing in a narrow beam.

2. The assembly as set forth in claim 1, wherein said frequency range of light which is directed by the beam splitter of the transponder, to the photodiode thereof, comprises at least a portion of the frequency range of the light emitted by the light emitting diode of the at least one interrogator;

and wherein the frequency range which is directed by the beam splitter of the interrogator, to the photodiode thereof, comprises at least a portion of the frequency range of the light emitted by the light emitting diode of the transponder.

3. The assembly as set forth in claim 1, further comprising a means for decoding said first electrical signal into an easily understandable form.

4. The assembly as set forth in claim 3, wherein said means for decoding comprises a microprocessor.

5. The assembly as set forth in claim 4, wherein said light emitting diodes emit light in the infrared range.

6. The assembly as set forth in claim 5, wherein at least one of said light emitting diodes comprises a gallium arsenide (GaAs) infrared emitting diode.

7. The assembly as set forth in claim 5, wherein at least one of said light emitting diodes comprises a GaAIAs infrared emitting diode.

8. The assembly as set forth in claim 1, wherein said housing of said transponder device further comprises an upper and a lower portion, said upper portion including said spectral filter and a reflecting mirror, said filter being oriented along a first axis, said lower portion of said housing including said dichroic beam splitter, said photodiode, and said light emitting diode, said dichroic beam splitter being oriented along a second axis, wherein said upper portion and said first axis are rotated relative to the lower portion, by a stepper motor through a 360 degree scanning field, and wherein said reflecting mirror maintains the optical alignments of the dichroic beam splitter and the spectral filter.

9. The assembly as set forth in claim 4, further comprising means for displaying said decoded information of said first electrical signal in a manner which is understandable by a user.

10. The assembly as set forth in claim 9, wherein said means for displaying the information comprises a video display.

11. The assembly as set forth in claim 1, wherein said means by which a user may produce a second electrical signal comprises a microphone.

12. The assembly as set forth in claim 1, wherein said means by which a user may produce a second electrical signal comprises a keyboard and microprocessor interface.

13. An interrogator device comprising:

a housing having a light receiving opening therein;

a spectral filter, mounted within said light receiving opening, which permits a specific frequency bandwidth of incident light to enter into and exit from said housing, said bandwidth including a first frequency for transmission and a second frequency for reception;

a dichroic beam splitter, mounted in optical receiving alignment with said spectral filter, for reflecting and transmitting selected portions of said specific frequency bandwidth;

a photodiode, mounted in optical receiving alignment with said dichroic beam splitter, for receiving one of said selected portions which includes said second frequency, and converting same into a first electrical signal;

a solar noise rejection circuit, through which circuit the first electrical signal is directed, which includes a pair of amplifiers coupled via a feedback loop whereby constant level solar noise components of the first electrical signal are subtracted therefrom;

means by which a user may produce a second electrical signal; and

a light emitting diode, aligned in light transmitting alignment with said dichroic beam splitter, for converting said second electrical signal into an emitted light signal which comprises the first frequency range within said specific frequency bandwidth, and emitting said light signal through said spectral filter and out of said housing in a narrow beam.

14. The device as set forth in claim 13, wherein the device is mounted within the optical sight of a pair of binoculars.

15. The device as set forth in claim 13, wherein the light emitting diode comprises a GaAIAs element.

16. A transponder device comprising:

a housing having a light receiving opening therein;

a spectral filter, mounted within said light receiving opening, which permits a specific frequency bandwidth of incident light to enter into and exit from said housing, said bandwidth including a first frequency for transmission and a second frequency for reception;

a dichroic beam splitter, mounted in optical receiving alignment with said spectral filter, for reflecting and transmitting selected portions of said specific frequency bandwidth;

a photodiode, mounted in optical receiving alignment with said dichroic beam splitter, for receiving one of said selected portions which includes said second frequency, and converting same into a first electrical signal;

means by which a user may produce a second electrical signal;

a light emitting diode, aligned in light transmitting alignment with said dichroic beam splitter, for converting said second electrical signal into an emitted light signal which comprises the first frequency range within said specific frequency bandwidth, and emitting said light signal through said spectral filter and out of said housing in a narrow beam;

said housing further comprising an upper and a lower portion, said upper portion including said spectral filter and a reflecting mirror, said filter being oriented along a first axis, said lower portion of said housing including said dichroic beam splitter, said photodiode, and said light emitting diode, said dichroic beam splitter being oriented along a second axis, wherein said upper portion and said first axis are rotated relative to the lower portion, by a stepper motor through a 360 degree scanning field, and wherein said reflecting mirror maintains the optical alignments of the dichroic beam splitter and the spectral filter.

17. The device as set forth in claim 16, wherein the light emitting diode comprises a GaAs element.

18. The device as set forth in claim 16, wherein said housing further comprises a selectably rotating portion which includes the light receiving opening such that the transponder may scan for, and receive light from, a wide angular field.

19. The transponder device as set forth in claim 18, further comprising means for selectively rotating said rotating portion to scan for a signal of the second frequency and a source of same, and means for stopping said rotating portion, in directional alignment with said source.

20. A covert communication device, comprising at least one interrogator device and at least one transponder device, wherein each of said interrogator devices comprises:

a housing having a light receiving opening therein;

a spectral filter, mounted within said light receiving opening, which permits a specific frequency bandwidth of incident light to enter into and exit from said housing, said bandwidth including a first frequency for transmission and a second frequency for reception;

a dichroic beam splitter, mounted in optical receiving alignment with said spectral filter, for reflecting and transmitting selected portions of said specific frequency bandwidth;

a photodiode, mounted in optical receiving alignment with said dichroic beam splitter, for receiving one of said selected portions which includes said second frequency, and converting same into a first electrical signal;

means by which a user may produce a second electrical signal; and

a light emitting diode, aligned in light transmitting alignment with said dichroic beam splitter, for converting said second electrical signal into an emitted light signal which comprises the first frequency range within said specific frequency bandwidth, and emitting said light signal through said spectral filter and out of said housing in a narrow beam,

and wherein each of said at least one transponder devices comprises;

a housing having a light receiving opening therein;

a spectral filter, mounted within said light receiving opening, which permits a specific frequency bandwidth of incident light to pass into and out of said housing, said bandwidth including a first frequency for transmission and a second frequency for reception;

a dichroic beam splitter, mounted in optical receiving alignment with said spectral filter, for reflecting and transmitting selected portions of said specific frequency bandwidth;

a photodiode, mounted in optical receiving alignment with said dichroic beam splitter, for receiving one of said selected portions which includes said second frequency, and converting same into a first electrical signal;

means by which a user may produce a second electrical signal; and

a light emitting diode, aligned in light transmitting alignment with said dichroic beam splitter, for converting said second electrical signal into an emitted light signal which comprises the first frequency range within said specific frequency bandwidth, and emitting said light signal through said spectral filter and out of said housing in a narrow beam,

wherein said housing further comprises an upper and a lower portion, said upper portion including said spectral filter and a reflecting mirror, said filter being oriented along a first axis, said lower portion of said housing including said dichroic beam splitter, said photodiode, and said light emitting diode, said dichroic beam splitter being oriented along a second axis, wherein said upper portion and said first axis are rotated relative to the lower portion, by a stepper motor through a 360 degree scanning field, and wherein said reflecting mirror maintains the optical alignments of the dichroic beam splitter and the spectral filter.

21. The covert communication device as set forth in claim 20, wherein said transponder further comprises means for selectively rotating said upper portion to scan for a signal of the second frequency and a source of same, and means for stopping said upper portion, in directional alignment with said source.

22. The covert communication device as set forth in claim 21, further including a microprocessor which controls said means for selectively rotating and said means for stopping said upper portion in accordance with the reception and identification of a specific code.

23. An infrared identification and communication assembly, including at least two devices, each of which comprises:

a housing having a light receiving opening therein;

a spectral filter, mounted within said light receiving opening, which permits a frequency bandwidth of incident light to enter into and exit from said housing, said bandwidth including first and second frequencies, wherein one of said first and second frequencies comprises a transmitted frequency and the other of the first and second frequencies comprises a received frequency;

a dichroic beam splitter, mounted in optical receiving alignment with said spectral filter, for reflecting and passing therethrough selected portions of said frequency bandwidth, wherein said selected portions which are reflected include one of said first and second frequencies, and said selected portions which pass therethrough include the other of the first and second frequencies;

a photodiode, mounted in optical receiving alignment with said dichroic beam splitter, for receiving said received frequency, and converting same into a first electrical signal;

means by which a user may produce a second electrical signal;

a light emitting diode, aligned in light transmitting alignment with said dichroic beam splitter, for converting said second electrical signal into a light signal comprising the transmitted frequency, and emitting said light signal through said spectral filter and out of said housing in a narrow beam;

wherein one of the devices comprises a transponder device and said housing of said transponder device further comprises an upper and a lower portion, said upper portion including said spectral filter and a reflecting mirror, said filter being oriented along a first axis, said lower portion of said housing including said dichroic beam splitter, said photodiode, and said light emitting diode, said dichroic beam splitter being oriented along a second axis, wherein said upper portion and said first axis are rotated relative to the lower portion, by a stepper motor through a 360 degree scanning field, and wherein said reflecting mirror maintains the optical alignments of the dichroic beam splitter and the spectral filter.