Agile-beam laser array transmitter

• US 8,301,027 B2
• Filed: 12/17/2008
• Issued: 10/30/2012
• Est. Priority Date: 05/02/2008
• Status: Active Grant

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Shaw, Gary A., Candell, Lawrence M.
• Primary Examiner(s): Sedighian, M. R.
• Application Number:
  US12/316,828
• Publication Number:
  US 20100046953A1
• Time in Patent Office: 1,413 Days
• Field of Search: 398/115, 398/116, 398/118, 398/164, 398/156, 398/151, 398/140, 398/131, 398/129, 398/88, 398/41, 398/42, 398/43, 398/66, 398/82, 398/130
• US Class Current: 398/88
• CPC Class Codes: G01S 7/4815 using multiple transmitters
• CPC Class Codes: H01S 5/005 Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping H01S5/026, H01S5/18388 take precedence
• CPC Class Codes: H01S 5/4031 Edge-emitting structures
• CPC Class Codes: H01S 5/4087 emitting more than one wavelength
• CPC Class Codes: H01S 5/423 having a vertical cavity

Abstract

An Agile-Beam Laser Array Transmitter (ABLAT) uses an array of emitters and an array of lenses to project electromagnetic beams over a wide angular coverage area in the far field. Differences in the separation pitches of the two arrays allows the ABLAT to project beams to contiguous and/or overlapping positions, depending on the ratio of the separation pitches and the lens focal length. Compared to other beam steering technology, the ABLAT is a smaller, lighter, and more efficient means of projecting beams over wider angular coverage areas. Various embodiments can be used in any beam steering application, including, but not limited to: free-space optical communications; light detection and ranging (lidar); optical scanning (e.g., retinal or bar-code scanning); display projection; image capture; optical character recognition; scanning laser microscopy; non-destructive testing; printing; facsimiles; map making; web inspection; color print processing; phototypesetting and platemaking; laser marking; material processing; DNA analysis; and drug discovery.

Claims

1. An apparatus for projecting an electromagnetic beam, the apparatus comprising:

an array of electromagnetic emitters, the emitters configured to generate electromagnetic beams;

an array of lenses positioned to project the electromagnetic beams to the selectable far-field position,

the array of electromagnetic emitters further comprising subarrays of N electromagnetic emitters per subarray, each subarray sharing a common lens,

the electromagnetic emitters within each subarray having a first separation pitch between the adjacent electromagnetic emitters, the lenses in the array of lenses having a second separation pitch between the adjacent lenses, and the subarrays having a third separation pitch between the adjacent subarrays,

the first and second separation pitches being different from each other and having a difference which, in combination with the focal lengths of the lenses, defines a step size in projecting the electromagnetic beams to a selectable far-field position within an angular coverage area.

2. The apparatus of claim 1, wherein the electromagnetic emitters emit optical radiation.

3. The apparatus of claim 2, wherein the electromagnetic emitters are vertical-cavity surface-emitting lasers (VCSELs).

4. The apparatus of claim 1, wherein the first separation pitch is greater than the second separation pitch.

5. The apparatus of claim 1, wherein the second separation pitch is greater than the first separation pitch.

6. The apparatus of claim 1, wherein the electromagnetic beams are combined incoherently.

7. The apparatus of claim 1, wherein the array of electromagnetic emitters and the array of lenses are aligned to project the electromagnetic beams to contiguous locations, the contiguous locations substantially covering the angular coverage area.

8. The apparatus of claim 1, wherein the array of emitters and the array of lenses are positioned to project the electromagnetic beams on overlapping areas within the angular coverage area.

9. The apparatus of claim 8, further comprising a control circuit configured to modulate the electromagnetic beams.

10. The apparatus of claim 9, wherein the electromagnetic beams projected on overlapping areas are of different wavelengths.

11. The apparatus of claim 1, further comprising a planar surface upon which the array of electromagnetic emitters is situated.

12. The apparatus of claim 1, further comprising a curved surface upon which the array of electromagnetic emitters is situated.

13. The apparatus of claim 1, further comprising a faceted surface upon which the array of electromagnetic emitters and the array of lenses are situated.

14. The apparatus of claim 1, wherein the subarrays are multidimensional.

15. The apparatus of claim 1, wherein the subarrays emit electromagnetic radiation at different wavelengths.

16. The apparatus of claim 1, further comprising a control circuit configured to control the emitters in a selectable manner.

17. The apparatus of claim 16, wherein the control circuit controls at least one of the following parameters:

beam size;

beam angle;

temporal beam modulation;

spatial beam modulation; and

number of beams emitted simultaneously.

18. The apparatus of claim 17, wherein the control circuit is configured to be coupled to the array of emitters in a hybridized manner.

19. An apparatus for projecting an electromagnetic beam, the apparatus comprising:

an array of electromagnetic emitters, configured to be controlled by an emitter controller and, the emitters configured to generate electromagnetic beams;

an array of lenses positioned to project the electromagnetic beams to a selectable far-field position within an angular coverage area,

the array of electromagnetic emitters further comprising subarrays of N electromagnetic emitters per subarray, each subarray sharing a common lens,

the electromagnetic emitters within each subarray having a first separation pitch between the adjacent electromagnetic emitters, the lenses in the array of lenses having a second separation pitch between the adjacent lenses, and the subarrays having a third separation pitch between the adjacent subarrays,

the first and second separation pitches being different from each other; and

a receiver, reference beacon generator, and imaging system, the imaging system configured to detect the reference beacon and provide an input to the emitter controller to activate a subset of the emitters to project the electromagnetic beam onto the receiver.

20. The apparatus of claim 19, wherein the receiver and the reference beacon are aligned along the same axis.

21. The apparatus of claim 19, wherein the receiver and the reference beacon are aligned along different axes.

22. A method for projecting an electromagnetic beam, the method comprising:

emitting an array of electromagnetic beams, said array including subarrays of electromagnetic beams, the beams in each subarray having a first separation pitch between the adjacent electromagnetic beams; and

projecting the electromagnetic beams to respective selectable far-field positions within an angular coverage area through an array of lenses having a second separation pitch between the adjacent lenses,

wherein projecting said electromagnetic beams includes projecting the electromagnetic beams emitted by each subarray through a lens common to said subarray,

wherein projecting the electromagnetic beams to respective selectable far-field positions is performed as a function of a second separation pitch, different from the first separation pitch, the first separation pitch and the second separation pitch having a difference which, in combination with a focal length, defines a step size in projecting the electromagnetic beams to the selectable far-field position.

23. The method of claim 22 wherein emitting electromagnetic beams further includes emitting optical radiation.

24. The method of claim 23, wherein the electromagnetic beams are provided by electromagnetic emitters, including vertical-cavity surface-emitting lasers (VCSELs).

25. The method of claim 22 wherein the first separation pitch is greater than the second separation pitch.

26. The method of claim 22 wherein the second separation pitch is greater than the first separation pitch.

27. The method of claim 22 further including incoherently combining the electromagnetic beams.

28. The method of claim 22 wherein the selectable far-field positions are contiguous locations that substantially cover the angular coverage area.

29. The method of claim 22 wherein projecting the electromagnetic beams to a selectable far-field position further includes projecting plural electromagnetic beams to an overlapping area.

30. The method of claim 29, further comprising modulating the electromagnetic beams.

31. The method of claim 30, wherein the plural electromagnetic beams projected on the overlapping area are of different wavelengths.

32. The method of claim 22 wherein emitting electromagnetic beams further includes emitting electromagnetic beams from a planar surface.

33. The method of claim 22 wherein emitting electromagnetic beams further includes emitting electromagnetic beams from a curved surface.

34. The method of claim 22 wherein emitting electromagnetic beams further includes emitting electromagnetic beams from a faceted surface.

35. The method of claim 22, wherein emitting the array of electromagnetic beams further includes emitting multidimensional arrays of electromagnetic beams.

36. The method of claim 22, wherein emitting the array of electromagnetic beams further includes emitting electromagnetic beams at different wavelengths.

37. The method of claim 22 further comprising controlling the emission of the electromagnetic beams in a selectable manner.

38. The method of claim 37, wherein controlling the emission of the electromagnetic beams includes controlling at least one of the following:

beam size;

beam angle;

temporal beam modulation;

spatial beam modulation; and

number of beams emitted simultaneously.

39. A method for projecting an electromagnetic beam, the method comprising:

emitting an array of electromagnetic beams, said array including subarrays of electromagnetic beams, the beams in each subarray having a first separation pitch between the adjacent electromagnetic beams;

projecting the electromagnetic beams to respective selectable far-field positions within an angular coverage area through an array of lenses having a second separation pitch between the adjacent lenses, wherein said projecting is performed as a function of a second separation pitch different from the first separation pitch,

wherein projecting the electromagnetic beams includes projecting the electromagnetic beams emitted by each subarray through a lens common to said subarray;

detecting a reference beacon; and

controlling emission and projection of at least a subset of the electromagnetic beams in response to the detected reference beacon.

40. The method of claim 39, wherein controlling emission and projection of at least a subset of the electromagnetic beams includes projecting at least one electromagnetic beam onto a receiver.

41. The method of claim 40, wherein projecting at least one electromagnetic beam further includes projecting an electromagnetic beam along an axis aligned with the reference beacon.

42. The method of claim 40, wherein projecting at least one electromagnetic beam further includes projecting an electromagnetic beam along an axis not aligned with the reference beacon.

43. A method for projecting an electromagnetic beam, the method comprising:

emitting an array of electromagnetic beams by emitters adjacent to each other, said array including subarrays of electromagnetic beams, the beams in each subarray having a first separation pitch between the adjacent electromagnetic beams;

projecting the electromagnetic beams to respective selectable far-field positions within an angular coverage area through an array of lenses having a second separation pitch between the adjacent lenses, wherein said projecting is performed as a function of the second separation pitch different from the first separation pitch, wherein projecting the electromagnetic beams includes projecting the electromagnetic beams emitted by each subarray through a lens common to said subarray;

detecting a reference beacon; and

controlling emission and projection of at least a subset of the electromagnetic beams in response to the detected reference beacon.

44. The method of claim 43, wherein emitting electromagnetic beams further includes emitting optical radiation.

45. An apparatus for projecting an electromagnetic beam, comprising:

an array of lenses having a first separation pitch between adjacent lenses; and

an array of electromagnetic emitters comprising subarrays of N electromagnetic emitters, each subarray having a second separation pitch between the adjacent emitters, the second separation pitch being different from the first separation pitch,

the first and second separation pitches having a difference which, in combination with the focal length of the lenses, defines a step size in projection the electromagnetic beams to a selectable far-field position within an angular coverage area, the emitters configured to generate electromagnetic beams, each electromagnetic beam filling a solid angle of a respective lens, the solid angle corresponding to the selectable far-field position,

the array of electromagnetic emitters having a third separation pitch between the adjacent subarrays, the third separation pitch being different from the first and second separation pitches.

46. The apparatus of claim 45, wherein the electromagnetic emitters are vertical-cavity surface-emitting lasers (VCSELs).

47. The apparatus of claim 45, further including a control circuit configured to control at least one of the following parameters:

beam size;

beam angle;

temporal beam modulation;

spatial beam modulation; and

number of beams emitted simultaneously.

48. A method for projecting an electromagnetic beam, the method comprising:

emitting electromagnetic beams at a first separation pitch;

filling respective solid angles at a second separation pitch with the electromagnetic beams, the second separation pitch being different from the first separation pitch and having a difference which in combination with a focal length defines a step size in projecting the electromagnetic beams to a selectable far-field position within an angular coverage area; and

projecting the electromagnetic beams to respective selectable far-field positions within an angular coverage area, the selectable far-field positions corresponding to the respective solid angles,

wherein emitting the electromagnetic beams includes emitting at least one subset of the electromagnetic beams at a third separation pitch, different from the first and second separation pitches, and wherein projecting said electromagnetic beams includes refracting the at least one subset of electromagnetic beams emitted at the third separation pitch through a common lens.

49. The method of claim 48, wherein emitting electromagnetic beams includes emitting optical radiation.

50. The method of claim 48, further including controlling at least one of the following parameters:

beam size;

beam angle;

temporal beam modulation;

spatial beam modulation; and

number of beams emitted simultaneously.

51. An apparatus for projecting an electromagnetic beam, comprising:

an array of electromagnetic emitters, said array comprising subarrays of N emitters, each subarray having a first separation pitch between adjacent emitters, the emitters configured to generate electromagnetic beams; and

an array of lenses having a second separation pitch between adjacent lenses, the first and second separation pitches being different from each other, the lenses being positioned to project the electromagnetic beams to a selectable far-field position within an angular coverage area;

the subarrays of N electromagnetic emitters having a third separation pitch, each subarray sharing a common lens, and the number of common lenses being reduced by N relative to an array of electromagnetic emitters without subarrays; and

a receiver, reference beacon generator, and imaging system, the imaging system configured to detect the reference beacon and provide an input to the emitter controller to activate a subset of the emitters to project the electromagnetic beams onto the receiver.

52. The apparatus of claim 51 wherein the subarrays are multidimensional.

53. The apparatus of claim 51 wherein the subarrays emit electromagnetic radiation at different wavelengths.

54. The apparatus of claim 51 wherein the electromagnetic emitters emit optical radiation.

55. The apparatus of claim 51 wherein the electromagnetic emitters are vertical-cavity surface-emitting lasers (VCSELs).

56. The apparatus of claim 51 wherein the first separation pitch is greater than the second separation pitch.

57. The apparatus of claim 51 wherein the second separation pitch is greater than the first separation pitch.

58. The apparatus of claim 51 wherein the electromagnetic beams are combined incoherently.

59. The apparatus of claim 51 wherein the difference in first and second separation pitches in combination with the focal lengths of the lenses defines a step size in projecting the electromagnetic beams to the selectable far-field position.

60. The apparatus of claim 51 wherein the array of electromagnetic emitters and the array of lenses are aligned to project the electromagnetic beams to contiguous locations, the contiguous locations substantially covering the angular coverage area.

61. The apparatus of claim 51 wherein the array of emitters and the array of lenses are positioned to project the electromagnetic beams on overlapping areas within the angular coverage area.

62. The apparatus of claim 61 further comprising a control circuit configured to modulate the electromagnetic beams.

63. The apparatus of claim 62 wherein the electromagnetic beams projected on overlapping areas are of different wavelengths.

64. The apparatus of claim 51 further comprising a planar surface upon which the array of electromagnetic emitters is situated.

65. The apparatus of claim 51 further comprising a curved surface upon which the array of electromagnetic emitters is situated.

66. The apparatus of claim 51 further comprising a faceted surface upon which the array of electromagnetic emitters and the array of lenses are situated.

67. The apparatus of claim 51 further comprising a control circuit configured to control the emitters in a selectable manner.

68. The apparatus of claim 67 wherein the control circuit controls at least one of the following parameters:

beam size;

beam angle;

temporal beam modulation;

spatial beam modulation; and

number of beams emitted simultaneously.

69. The apparatus of claim 68 wherein the control circuit is configured to be coupled to the array of emitters in a hybridized manner.

70. The apparatus of claim 51 wherein the receiver and the reference beacon are aligned along the same axis.

71. The apparatus of claim 51 wherein the receiver and the reference beacon are aligned along different axes.

72. A method for projecting an electromagnetic beam, the method comprising:

emitting an array of electromagnetic beams by emitters, said array including subarrays of electromagnetic beams, the beams in each subarray having a first separation pitch between the adjacent electromagnetic beams;

projecting the electromagnetic beams to respective selectable far-field positions within an angular coverage area through an array of lenses having a second separation pitch between the adjacent lenses, wherein said projecting is performed as a function of lenses having a second separation pitch different from the first separation pitch,

wherein projecting the electromagnetic beams includes projecting the electromagnetic beams emitted by each subarray through a lens common to said subarray;

detecting a reference beacon; and

controlling emission and projection of at least a subset of the electromagnetic beams in response to the detected reference beacon.

73. The method of claim 72 wherein emitting electromagnetic beams further includes emitting electromagnetic beams in multidimensional arrays separated by the third separation pitch.

74. The method of claim 72 wherein emitting electromagnetic beams further includes emitting electromagnetic beams at different wavelengths.

75. The method of claim 72 wherein emitting electromagnetic beams further includes emitting optical radiation.

76. The method of claim 75 wherein the electromagnetic beams are provided by electromagnetic emitters, including vertical-cavity surface-emitting lasers (VCSELs).

77. The method of claim 72 wherein the first separation pitch is greater than the second separation pitch.

78. The method of claim 72 wherein the second separation pitch is greater than the first separation pitch.

79. The method of claim 72 further including incoherently combining the electromagnetic beams.

80. The method of claim 72 wherein the difference in separation pitches in combination with a focal length defines a step size in projecting the electromagnetic beams to the selectable far-field position.

81. The method of claim 72 wherein the selectable far-field positions are contiguous locations that substantially cover the angular coverage area.

82. The method of claim 72 wherein projecting the electromagnetic beams to a selectable far-field position further includes projecting plural electromagnetic beams to an overlapping area.

83. The method of claim 82 further comprising modulating the electromagnetic beams.

84. The method of claim 82 wherein the plural electromagnetic beams projected on the overlapping area are of different wavelengths.

85. The method of claim 72 wherein emitting electromagnetic beams further includes emitting electromagnetic beams from a planar surface.

86. The method of claim 72 wherein emitting electromagnetic beams further includes emitting electromagnetic beams from a curved surface.

87. The method of claim 72 wherein emitting electromagnetic beams further includes emitting electromagnetic beams from a faceted surface.

88. The method of claim 72 further comprising controlling the emission of the electromagnetic beams in a selectable manner.

89. The method of claim 88 wherein controlling the emission of the electromagnetic beams includes controlling at least one of the following:

beam size;

beam angle;

temporal beam modulation;

spatial beam modulation; and

number of beams emitted simultaneously.

90. The method of claim 89 wherein controlling emission and projection of at least a subset of the electromagnetic beams includes projecting at least one electromagnetic beam onto a receiver.

91. The method of claim 72 wherein projecting at least one electromagnetic beam further includes projecting an electromagnetic beam along an axis aligned with the reference beacon.

92. The method of claim 72 wherein projecting at least one electromagnetic beam further includes projecting an electromagnetic beam along an axis not aligned with the reference beacon.