Single detector receiver for multi-beam LADAR systems

• US 20060197936A1
• Filed: 03/01/2005
• Published: 09/07/2006
• Est. Priority Date: 03/01/2005
• Status: Active Grant

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Inventors: Liebman, Lionel D., Larson, Don A., Flockencier, Stuart W., Flowers, Edward M.
• Granted Patent: US 7,375,804 B2
• Time in Patent Office: Days
• US Class Current: 356/5.01
• CPC Class Codes: G01S 17/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S17/46
• CPC Class Codes: G01S 7/4818 using optical fibres
• CPC Class Codes: G01S 7/486 Receivers
• CPC Class Codes: G01S 7/499 using polarisation effects

Abstract

A LADAR apparatus and a method for use in receiving a LADAR signal are disclosed. The apparatus includes an optical pickup capable of picking up a plurality of optical signals; a timing synchronization reference; a time domain multiplexer capable of multiplexing the optical signals into a multiplexed optical signal relative to the timing synchronization reference; and an optical detector capable of detecting the multiplexed optical signal. The method include time domain multiplexing a plurality of LADAR signals into multiplexed LADAR signal; detecting the multiplexed LADAR signal; and demultiplexing the detected LADAR signal.

Claims

1. A LADAR apparatus, comprising:

an optical pickup capable of picking up a plurality of optical signals;

a timing synchronization reference;

a time domain multiplexer capable of multiplexing the optical signals into a multiplexed optical signal relative to the timing synchronization reference; and

an optical detector capable of detecting the multiplexed optical signal.

2. The LADAR apparatus of claim 1, wherein the optical pickup comprises a plurality of fibers.

3. The LADAR apparatus of claim 1, wherein the timing synchronization reference comprises a backscatter reference or a laser trigger signal.

4. The LADAR apparatus of claim 1, wherein the time domain multiplexer includes:

a delay for each of the optical signals, each delay being staggered and being measured relative to the timing synchronization reference; and

a combiner capable of combining the delayed optical signals into the multiplexed signal.

5. The LADAR apparatus of claim 4, wherein the delay comprises varying lengths of optical fiber, each optical signal propagating through a unique length of fiber.

6. The LADAR apparatus of claim 5, wherein the delay further comprises:

a plurality of optical circulators, one for each of the optical signals, positioned at one end of the respective length of optical fiber; and

a plurality of reflectors, one for each of the optical signals, positioned at the opposite end of the respective length of optical fiber.

7. The LADAR apparatus of claim 4, wherein the combiner comprises one of a tree coupler or a cascade of tap couplers.

8. The LADAR apparatus of claim 4, wherein the combiner comprises:

the active surface of the optical detector; and

a lens focusing the picked-up, delayed optical signals onto the active surface.

9. The LADAR apparatus of claim 1, further comprising a PIN detector tapping the multiplexed optical signal.

10. The LADAR apparatus of claim 1, further comprising:

a second optical detector; and

at least one of a switch and a polarization splitter through which the second optical detector receives the multiplexed optical signal.

11. The LADAR apparatus of claim 1, further comprising a variable optical attenuator.

12. The LADAR apparatus of claim 11, wherein the variable optical attenuator comprises a single channel variable optical attenuator capable of attenuating the multiplexed optical signal.

13. The LADAR apparatus of claim 11, wherein the variable optical attenuator comprises a multi-channel variable optical attenuator capable of individually attenuating the plurality of optical signals.

14. The LADAR apparatus of claim 1, wherein the optical detector comprises an avalanche photodiode.

15. A LADAR apparatus, comprising:

means for picking up a plurality of optical signals;

means for time domain multiplexing the optical signals; and

means for detecting the multiplexed optical signal.

16. The LADAR apparatus of claim 15, wherein the pickup means comprises a plurality of fibers.

17. The optical detecting apparatus of claim 15, wherein the time domain multiplexing means includes:

means for synchronizing the multiplexing;

means for delaying each of the optical signals by a staggered amount measured relative to the synchronizing means; and

means for combining the delayed optical signals into the multiplexed signal.

18. The LADAR apparatus of claim 17, wherein the synchronizing means comprises a backscatter reference or a laser trigger signal.

19. The LADAR apparatus of claim 17, wherein the delaying means comprises varying lengths of optical fiber, each optical signal propagating through a unique length of fiber.

20. The LADAR apparatus of claim 19, wherein the delaying means further comprises:

a plurality of optical circulators, one for each of the optical signals, positioned at one end of the respective length of optical fiber; and

a plurality of reflectors, one for each of the optical signals, positioned at the opposite end of the respective length of optical fiber.

21. The LADAR apparatus of claim 17, wherein the combining means comprises one of a tree coupler or a cascade of tap couplers.

22. The LADAR apparatus of claim 17, wherein the combining means comprises:

the active surface of the optical detector; and

a lens focusing the picked-up, delayed optical signals onto the active surface.

23. The LADAR apparatus of claim 15, further comprising a PIN detector tapping the multiplexed optical signal.

24. The LADAR apparatus of claim 15, further comprising:

second means for detecting the multiplexed optical signal; and

means for directing the multiplexed optical signal to the second detecting means.

25. The LADAR apparatus of claim 24, wherein the directing means comprises at least one of a switch and a polarization splitter.

26. The LADAR apparatus of claim 15, further comprising a variable optical attenuator.

27. The LADAR apparatus of claim 15, wherein the detecting means comprises an avalanche photodiode.

28. A method, comprising:

time domain multiplexing a plurality of LADAR signals into multiplexed LADAR signal;

detecting the multiplexed LADAR signal; and

demultiplexing the detected LADAR signal.

29. The method of claim 28, wherein time domain multiplexing the LADAR signals includes:

inserting a unique, staggered delay into each of the LADAR signals; and

combining the delayed LADAR signals.

30. The method of claim 29, wherein inserting the delays includes propagating the received LADAR signals through varied lengths of optical fibers.

31. The method of claim 30, wherein inserting the delays further includes circulating the LADAR fibers through the optical fibers to a respective reflector and back through a lens.

32. The method of claim 29, wherein combining the delayed LADAR signals includes combining them through one of a tree coupler or a cascade of tap couplers.

33. The method of claim 29, wherein the wherein combining the delayed LADAR signals includes focusing the delayed LADAR signals onto the active surface of the optical detector.

34. The method of claim 28, further comprising detecting the combined LADAR signals.

35. The method of claim 28, further comprising:

splitting multiplexed LADAR signal; and

detecting the split multiplexed LADAR signal.

36. The method of claim 28, further comprising switching the multiplexed LADAR signal between a first and a second detector.

37. The method of claim 28, further comprising attenuating the multiplexed LADAR signal.

38. A LADAR apparatus, comprising:

means for time domain multiplexing a plurality of LADAR signals into multiplexed LADAR signal;

means for detecting the multiplexed LADAR signal; and

means for demultiplexing the detected LADAR signal.

39. The LADAR apparatus of claim 38, wherein time domain multiplexing means includes:

means for inserting a unique, staggered delay into each of the LADAR signals; and

means for combining the delayed LADAR signals.

40. The LADAR apparatus of claim 39, wherein the inserting means includes means for propagating the received LADAR signals over varied distances.

41. The LADAR apparatus of claim 40, wherein the inserting means further includes means for circulating the LADAR signals to a respective reflector and back through a lens.

42. The LADAR apparatus of claim 39, wherein the combining means includes one of a tree coupler or a cascade of tap couplers.

43. The LADAR apparatus of claim 39, wherein the wherein the combining means includes means for focusing the delayed LADAR signals onto the active surface of the optical detector.

44. The LADAR apparatus of claim 38, further comprising means for detecting the combined LADAR signals.

45. The LADAR apparatus of claim 38, further comprising:

means for splitting multiplexed LADAR signal; and

means for detecting the split multiplexed LADAR signal.

46. The LADAR apparatus of claim 38, further comprising means for switching the multiplexed LADAR signal between a first and a second detector.

47. The LADAR apparatus of claim 38, further comprising means for attenuating the multiplexed LADAR signal.