Combined LOAS and LIDAR system

• US 6,556,282 B2
• Filed: 09/04/2001
• Issued: 04/29/2003
• Est. Priority Date: 09/04/2001
• Status: Expired due to Fees

• Current Assignee: Rosemount Aerospace, Inc. (Rtx Corporation)
• Original Assignee: Rosemount Aerospace, Inc. (Rtx Corporation)
• Inventors: Ray, Mark D., Meneely, Clinton T., Jamieson, James R.
• Primary Examiner(s): Buczinski, Stephen C.
• Application Number:
  US09/946,057
• Publication Number:
  US 20030043363A1
• Time in Patent Office: 602 Days
• Field of Search: 359/629-640, 356/3-1-1, 356/28.5
• US Class Current: 356/4.01
• CPC Class Codes: B64D 45/08 optical
• CPC Class Codes: G01C 23/005 Flight directors indicating arrangements specially adapted for rotary gyroscopes G01C19/32
• CPC Class Codes: G01P 5/26 by measuring the direct influence of the streaming fluid on the properties of a detecting optical wave
• CPC Class Codes: G01S 17/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S17/46
• CPC Class Codes: G01S 17/58 Velocity or trajectory determination systems; Sense-of-movement determination systems
• CPC Class Codes: G01S 17/87 Combinations of systems using electromagnetic waves other than radio waves
• CPC Class Codes: G01S 17/88 Lidar systems specially adapted for specific applications
• CPC Class Codes: G01S 17/933 of aircraft or spacecraft
• CPC Class Codes: G01S 7/4802 using analysis of echo signal for target characterisation; Target signature; Target cross-section
• CPC Class Codes: G01S 7/481 Constructional features, e.g. arrangements of optical elements
• CPC Class Codes: G01S 7/4812 transmitted and received beams following a coaxial path
• CPC Class Codes: G01S 7/4813 Housing arrangements
• CPC Class Codes: G01S 7/4817 relating to scanning
• CPC Class Codes: G01S 7/483 Details of pulse systems

Abstract

A combined system of a LOAS and a LIDAR system comprises: a LIDAR arrangement of optical elements for generating a first coherent beam of light at a first predetermined wavelength; a LOAS arrangement of optical elements for generating a second coherent beam of light at a second predetermined wavelength; a dichroic filter optical element for directing the first and second coherent beams of light substantially on a first common optical path towards an aperture of a beam expander; at least one output optical element which directs both of the expanded first and second coherent beams of light from the system, the at least one output optical element also for receiving and directing reflections of the first and second coherent beams of light to the beam expander wherein the beam reflections are collected; and wherein the dichroic filter optical element separates and directs the collected light corresponding to the first coherent beam back to the LIDAR arrangement of optical elements for use in determining flow velocity, and separates and directs the collected light corresponding to the second coherent beam back to the LOAS arrangement of optical elements for use in detecting at least one object.

Claims

1. A combined system of a laser obstacle awareness system (LOAS) and a light detection and ranging (LIDAR) system for obstacle detection and flow velocity measurement, said combined system comprising:

a LIDAR arrangement of optical elements for generating a first coherent beam of light at a first predetermined wavelength;

a LOAS arrangement of optical elements for generating a second coherent beam of light at a second predetermined wavelength;

a beam expander;

a dichroic filter optical element for directing said first and second coherent beams of light substantially on a first common optical path towards an aperture of said beam expander, said beam expander being aligned to accept and expand said first and second coherent beams and exit said expanded first and second coherent beams along a second common optical path at an output thereof;

at least one output optical element, said second common optical path being incident on said at least one output optical element which directs both of said expanded first and second coherent beams of light from said system, said at least one output optical element also for receiving reflections of said first and second coherent beams of light and directing said reflections to said beam expander wherein said beam reflections are collected;

said dichroic filter optical element for separating the collected light corresponding to said first coherent beam from the collected light corresponding to said second coherent beam, the separated light corresponding to said first coherent beam being directed back to said LIDAR arrangement of optical elements, and the separated light corresponding to said second coherent beam being directed back to said LOAS arrangement of optical elements;

a first light detector for converting light representative of the separated light corresponding to said first coherent beam to first electrical signals representative thereof;

a second light detector for converting light representative of the separated light corresponding to said second coherent beam to second electrical signals representative thereof; and

processing means coupled to the first and second light detectors for detecting at least one object and determining flow velocity using said first and second electrical signals.

2. The combined system of claim 1 including beam converging optics disposed between the LIDAR arrangement of optical elements and the dichroic filter optical element for focusing the first coherent beam of light substantially at a spot in space a predetermined range from said system;

and wherein said at least one output optical element for receiving reflections of said first coherent beam of light from at least one particle at said spot in space and directing said particle reflections to said beam expander wherein said beam reflections are collected.

3. The combined system of claim 2 wherein the beam converging optics is operative to vary the range of the spot in space on which the first coherent beam of light is focused.

4. The combined system of claim 1 wherein the at least one output optical element comprises at least one common rotationally operated optical element, said second common optical path being incident on said at least one common rotationally operated optical element which directs both of said expanded first and second coherent beams of light from said system, said expanded first coherent beam of light being directed with a first predetermined pattern and said expanded second coherent beam of light being directed with a second predetermined pattern.

5. The combined system of claim 4 wherein the at least one common rotationally operated optical element also for receiving reflections of said second coherent beam of light from at least one object along said second predetermined pattern and directing said beam reflections to the beam expander wherein said beam reflections are collected.

6. The combined system of claim 4 wherein the first and second patterns are substantially the same.

7. The combined system of claim 4 wherein the at least one common rotationally operated optical element also for directing the expanded first coherent beam of light with the first predetermined pattern and the expanded second coherent beam of light with the second predetermined pattern in an azimuthal scan.

8. The combined system of claim 7 wherein the expanded first coherent beam of light with the first predetermined pattern and the expanded second coherent beam of light with the second predetermined pattern are directed substantially to common azimuth positions in the azimuthal scan.

9. The combined system of claim 7 wherein the second light detector converts the light reflections of the second coherent beam to the second electrical signals representative thereof for use by processing means in detecting at least one object;

and including means for determining substantially the azimuth position of the directed second coherent beam of light in the azimuthal scan thereof; and

wherein processing means is coupled to said azimuth position determining means for determining a location of the at least one detected object in range and azimuth.

10. The combined system of claim 7 wherein the LIDAR arrangement of optical elements includes optical elements for producing heterodyned light reflections of the first coherent beam;

wherein the first light detector converts said heterodyned light reflections to third electrical signals representative thereof for use by processing means in determining flow velocity; and

including means for determining substantially the azimuth position of the directed first coherent beam of light in the azimuthal scan thereof; and

wherein processing means is coupled to said azimuth position determining means for determining the flow velocity at different azimuth positions in the azimuthal scan.

11. The combined system of claim 4 wherein the at least one rotationally operated optical element includes:

a first rotationally operated optical element for receiving the expanded first and second coherent beams of light and directing said received beams therefrom with their respectively corresponding first and second predetermined patterns; and

a second rotationally operated optical element for receiving the first and second beams from said first rotationally operated optical element and directing said received beams with their predetermined patterns in an azimuthal scan.

12. The combined system of claim 11 wherein the first rotationally operated optical element comprises a mirrored optical element rotated at a predetermined nutation angle;

and wherein said expanded first and second coherent beams of light being received and reflected from a surface of said mirrored optical element.

13. The combined system of claim 11 wherein the first rotationally operated optical element comprises a dichroic wedge optical element which directs light substantially of the first coherent beam from a one surface thereof and directs light substantially of the second coherent beam from another surface thereof.

14. The combined system of claim 11 wherein the first rotationally operated optical element comprises a dichroic wobble mirror optical element which reflects light substantially of the first coherent beam from one surface thereof and directs light substantially of the second coherent beam from another surface thereof.

15. The combined system of claim 11 wherein the first rotationally operated optical element comprises a mirrored optical element having one surface inclined at a predetermined angle relative to a surface opposite thereto, said optical element being rotated about an axis normal to said opposite surface;

and wherein said expanded first and second beams being received and reflected from said inclined surface of said mirrored optical element.

16. The combined system of claim 11 wherein the first rotationally operated optical element comprises a Palmer mirror;

and wherein said expanded first and second beams being received and reflected from a surface of said Palmer mirror.

17. The combined system of claim 11 wherein the second rotationally operated optical element comprises a mirrored optical element;

and wherein the directed beams from said first rotationally operated optical element are received and reflected from a surface of said mirrored optical element.

18. The combined system of claim 11 wherein the second rotationally operated optical element is configured as a fold mirror.

19. The combined system of claim 11 wherein the first rotationally operated optical element is configured as a fold mirror.

20. The combined system of claim 11 wherein the first rotationally operated optical element is rotated at a rotational speed substantially greater than the rotational speed of the second rotationally operated optical element.

21. A block arrangement of optical elements for use as a transmitter/receiver for a light detection and ranging (LIDAR) system, said block arrangement comprising:

a plurality of glass modules aligned together as a block to form a plurality of optical paths therein and secured together to maintain said alignment;

a collimated light source for generating a coherent beam of light over at least one optical path in said block which guides said coherent beam of light to an exit point of said block;

a light detector;

said block for receiving a return coherent beam of light and configured to conduct said return coherent beam of light to said light detector over at least one other optical path formed in said block; and

wherein said block includes an opening for securing an acousto-optic modulator (AOM).

22. The block arrangement of claim 21 including a quarter wavelength plate secured at said exit point of said block;

wherein the generated beam of light exits the block through said quarter wavelength plate; and

wherein the return beam of light is received by the block through said quarter wavelength plate.

23. The block arrangement of claim 22 wherein the quarter wavelength plate is cemented to said block at said exit point thereof.

24. The block arrangement of claim 21 wherein two of the glass modules of the plurality are cemented together to form a first beam splitter that is disposed in the optical path of the generated coherent beam of light for passing light in a first polarization state and reflecting light in a second polarization state.

25. The block arrangement of claim 24 wherein the first beam splitter is also disposed in the path of the return coherent beam of light.

26. The block arrangement of claim 25 wherein the AOM is disposed in the optical path of the light reflected from the first beam splitter.

27. The block arrangement of claim 26 wherein another two glass modules of the plurality are cemented together to form a second beam splitter that is disposed in the optical paths of the return coherent beam of light and light exiting the AOM, said second beam splitter configured to guide portions of both of the return coherent beam of light and light exiting the AOM to the light detector.

28. The block arrangement of claim 26 wherein one of the glass modules of the plurality comprises a dove prism which is cemented to at least one other glass module to form an optical path for guiding the light reflected from the first beam splitter to the AOM.

29. The block arrangement of claim 21 wherein the plurality of glass modules are secured together by cementing with an adhesive.

30. The block arrangement of claim 29 wherein the adhesive comprises an ultraviolet cured optical adhesive.

31. The block arrangement of claim 21 wherein at least one of the glass modules of the plurality includes at least one polished surface for forming one optical path of the block by internal light reflection.

32. The block arrangement of claim 21 wherein the collimated light source comprises a laser diode.

33. The block arrangement of claim 21 wherein the light detector comprises a photodiode.

34. The block arrangement of claim 21 wherein the collimated light source is secured to one side of the block and the exit point is at another side of the block.

35. The block arrangement of claim 21 wherein the collimated light source is secured to one side of the block and the light detector is secured to another side of the block.

36. The block arrangement of claim 21 including a beam correction optical element disposed in the optical path of light exiting the AOM.

37. The block arrangement of claim 21 wherein two glass modules of the plurality are cemented together to form a beam splitter that is disposed in the optical path of the return coherent beam of light for guiding a portion of the return coherent beam of light to the light detector.

38. The block arrangement of claim 21 wherein the alignment of glass modules forms a direct line optical path for the coherent beam of light between the collimated light source and the exit point of the block.

39. The block arrangement of claim 21 wherein the optical paths of the generated and return coherent beams of light are colinear within the block.

40. A combined system of a laser obstacle awareness system (LOAS) and a light detection and ranging (LIDAR) system for obstacle detection and flow velocity measurement, said combined system comprising:

a LIDAR arrangement of optical elements for generating a first coherent beam of light at a first predetermined wavelength;

a LOAS arrangement of optical elements for generating a second coherent beam of light at a second predetermined wavelength;

a dichroic filter optical element for directing said first and second coherent beams of light substantially along a common optical path;

a scan head including a beam expander for accepting and expanding light from said common optical path; and

at least one output optical element, for directing both of said expanded first and second coherent beams of light from said scan head, said at least one output optical element also for receiving reflections of said first and second coherent beams of light and directing said reflections to said beam expander wherein said beam reflections are collected and returned to said dichroic filter optical element along said common optical path;

said dichroic filter optical element for separating the collected light corresponding to said first coherent beam from the collected light corresponding to said second coherent beam, the separated light corresponding to said first coherent beam being directed back to said LIDAR arrangement of optical elements, and the separated light corresponding to said second coherent beam being directed back to said LOAS arrangement of optical elements;

a first light detector for converting light representative of the separated light corresponding to said first coherent beam to first electrical signals representative thereof;

a second light detector for converting light representative of the separated light corresponding to said second coherent beam to second electrical signals representative thereof; and

processing means coupled to the first and second light detectors for detecting at least one object and determining flow velocity using said first and second electrical signals.

41. The combined system of claim 40 wherein the at least one output optical element of the scan head comprises at least one common rotationally operated optical element for directing both of said expanded first and second coherent beams of light from the scan head, said expanded first coherent beam of light being directed with a first predetermined pattern and said expanded second coherent beam of light being directed with a second predetermined pattern.

42. The combined system of claim 41 wherein the at least one common rotationally operated optical element also for receiving reflections of said second coherent beam of light from at least one object along said second predetermined pattern and directing said beam reflections to the beam expander wherein said beam reflections are collected and returned to said dichroic filter optical element along the common optical path.

43. The combined system of claim 41 wherein the first and second patterns are substantially the same.

44. The combined system of claim 41 wherein the at least one common rotationally operated optical element being rotated azimuthally by the scan head for directing both the expanded first coherent beam of light with the first predetermined pattern and the expanded second coherent beam of light with the second predetermined pattern in an azimuthal scan.

45. The combined system of claim 44 wherein the expanded first coherent beam of light with the first predetermined pattern and the expanded second coherent beam of light with the second predetermined pattern are directed substantially to common azimuth positions in the azimuthal scan.

46. The combined system of claim 41 wherein the at least one common rotationally operated optical element being rotated in elevation by the scan head for directing both the expanded first coherent beam of light with the first predetermined pattern and the expanded second coherent beam of light with the second predetermined pattern in an elevational scan.

47. The combined system of claim 44 wherein the expanded first coherent beam of light with the first predetermined pattern and the expanded second coherent beam of light with the second predetermined pattern are directed substantially to common azimuth positions in the elevational scan.

48. The combined system of claim 40 wherein the scan head is remotely located from the LOAS arrangement of optical elements and LIDAR arrangement of optical elements;

and wherein the optical path to the remote scan head comprises a fiber optic cable.

49. The combined system of claim 40 including a plurality of scan heads;

and an optical switch controllable to couple light between the common optical path and. a selected scan head of said plurality along a corresponding optical path.

50. The combined system claim 49 wherein each of the scan heads is remotely located from the LOAS arrangement of optical elements and LIDAR arrangement of optical elements;

and wherein each of the corresponding optical paths of the remote scan heads comprises a fiber optic cable.

51. The combined system of claim 49 wherein the optical switch comprises a flip mirror operated to rotate about at least one axis.

52. The combined system of claim 49 wherein the optical switch is fabricated using MEMS techniques.

53. The combined system of claim 40 including a plurality of scan heads;

and wherein light is directed between the common optical path and the plurality of scan heads along a corresponding plurality of optical paths.

54. A combined system of a laser obstacle awareness system (LOAS) and a light detection and ranging (LIDAR) system for obstacle detection and flow velocity measurement, said combined system comprising:

a LIDAR arrangement of optical elements for generating a first coherent beam of light at a first predetermined wavelength;

a LOAS arrangement of optical elements for generating a second coherent beam of light at a second predetermined wavelength;

a dichroic filter optical element for directing said first and second coherent beams of light substantially along a common optical path;

a scan head for accepting light from said common optical path; and

including at least one output optical element, for directing both of said first and second coherent beams of light from said scan head, said at least one output optical element also for receiving reflections of said first and second coherent beams of light and directing said reflections to said common optical path wherein said beam reflections are collected and returned to said dichroic filter optical element;

said dichroic filter optical element for separating the collected light corresponding to said first coherent beam from the collected light corresponding to said second coherent beam, the separated light corresponding to said first coherent beam being directed back to said LIDAR arrangement of optical elements, and the separated light corresponding to said second coherent beam being directed back to said LOAS arrangement of optical elements;

a first light detector for converting light representative of the separated light corresponding to said first coherent beam to first electrical signals representative thereof;

a second light detector for converting light representative of the separated light corresponding to said second coherent beam to second electrical signals representative thereof; and

processing means coupled to the first and second light detectors for detecting at least one object and determining flow velocity using said first and second electrical signals.

55. The combined system of claim 54 wherein the scan head is remotely located from the LOAS arrangement of optical elements and LIDAR arrangement of optical elements;

and wherein the optical path to the remote scan head comprises a fiber optic cable.

60. The combined system of claim 54 including a plurality of scan heads;

and wherein light is directed between the common optical path and the plurality of scan heads along a corresponding plurality of optical paths.

56. The combined system of claim 56 including a plurality of scan heads;

and an optical switch controllable to couple light between the common optical path and a selected scan head of said plurality along a corresponding optical path.

57. The combined system of claim 56 wherein each of the scan heads is remotely located from the LOAS arrangement of optical elements and LIDAR arrangement of optical elements;

and wherein each of the corresponding optical paths of the remote scan heads comprises a fiber optic cable.

58. The combined system of claim 56 wherein the optical switch comprises a flip mirror operated to rotate about at least one axis.

59. The combined system of claim 56 wherein the optical switch is fabricated using MEMS techniques.

61. A combined system of a laser obstacle awareness system (LOAS) and a light detection and ranging (LIDAR) system for obstacle detection and flow velocity measurement, said combined system comprising:

a LIDAR arrangement of optical elements for generating a first coherent beam of light at a first predetermined wavelength;

a LOAS arrangement of optical elements for generating a second coherent beam of light at a second predetermined wavelength;

a dichroic filter optical element for directing said first and second coherent beams of light substantially along a common optical path;

a plurality of scan heads;

an optical switch controllable to couple light between the common optical path and a selected scan head of said plurality along a corresponding optical path;

each scan head for accepting light from said optical switch; and

including at least one output optical element for directing both of said first and second coherent beams of light from said scan head, said at least one output optical element also for receiving reflections of said first and second coherent beams of light and directing said reflections to said optical switch wherein said beam reflections are collected and returned to said dichroic filter optical element; and

said dichroic filter optical element for separating the collected light corresponding to said first coherent beam from the collected light corresponding to said second coherent beam, the separated light corresponding to said first coherent beam being directed back to said LIDAR arrangement of optical elements for use in determining flow velocity, and the separated light corresponding to said second coherent beam being directed back to said LOAS arrangement of optical elements for use in detecting at least one object.

62. The combined system of claim 61 wherein each of the scan heads is remotely located from the LOAS arrangement of optical elements and LIDAR arrangement of optical elements;

and wherein each of the corresponding optical paths of the remote scan heads comprises a fiber optic cable.

63. The combined system of claim 61 wherein the optical switch comprises a flip mirror operated to rotate about at least one axis.

64. The combined system of claim 61 wherein the optical switch is fabricated using MEMS techniques.