Holographic structured light generator

• US 5,548,418 A
• Filed: 09/12/1995
• Issued: 08/20/1996
• Est. Priority Date: 01/14/1994
• Status: Expired due to Fees

• Current Assignee: DCS Corporation
• Original Assignee: DCS Corporation
• Inventors: Gaynor, Edwin S., Massimi, Michael S., Blase, William P., Isser, Abraham
• Primary Examiner(s): Lerner, Martin
• Assistant Examiner(s): Schuberg, Darren E.
• Application Number:
  US08/527,038
• Time in Patent Office: 343 Days
• Field of Search: 359/10, 359/11, 359/20, 359/28, 359/34, 356/347, 356/376, 385/30
• US Class Current: 359/20
• CPC Class Codes: G02B 5/32 Holograms used as optical elements
• CPC Class Codes: G03H 1/12 Spatial modulation, e.g. ghost imaging
• CPC Class Codes: G03H 2001/0224 Active addressable light modulator, i.e. Spatial Light Modulator [SLM] corresponding details, see subgroups of G03H2225/00
• CPC Class Codes: G03H 2001/0428 Image holography, i.e. an image of the object or holobject is recorded G03H1/0406 takes precedence; holographic microscope G03H2001/005
• CPC Class Codes: G03H 2001/0439 for recording Holographic Optical Element [HOE] HOE per se G02B5/32
• CPC Class Codes: G03H 2001/2207 Spatial filter, e.g. for suppressing higher diffraction orders
• CPC Class Codes: G03H 2210/22 2D SLM object wherein the object beam is formed of the light modulated by the SLM SLM per se G03H2001/0224
• CPC Class Codes: G03H 2223/16 Optical waveguide, e.g. optical fibre, rod
• CPC Class Codes: G03H 2223/53 Filtering the hologram information, i.e. the fringe pattern
• CPC Class Codes: G03H 2223/54 Filtering the holobject information
• CPC Class Codes: G03H 2227/03 Means for moving one component G03H1/0476, G03H2001/2695 take precedence

Abstract

The present invention is a holographic structured light generator (HSLG) for generating an array of an arbitrary number of laser beamlets from a single laser beam using a point laser light source and a hologram. In a first preferred embodiment of the present invention, a hologram having an image of four point sources in a common plane is fabricated using four point sources as the object beam, and a reference beam. A reconstruction beam, aligned identically with respect to the hologram as was the reference beam during fabrication of the hologram, is then directed at the hologram, generating the array of laser beamlets from the four point sources in the hologram. In a primary application of the HSLG, it is used to map the surface of an object in three dimensions. The HSLG is used with video cameras, computer image processing equipment and an optical spatial light modulator to yield 3-D data for use with CAD systems.

Claims

1. An apparatus for generating an array of electromagnetic beamlets comprising:

(a) a hologram having an image of three phase-controlled point sources;

(b) a reconstruction electromagnetic source producing a reconstruction beam;

(c) means for directing the reconstruction beam at the hologram; and

(d) means for aligning the reconstruction beam such that three phase-controlled beams are generated from the of the three phase-controlled point sources, said three phase-controlled beams overlapping each other and interfering with each other to produce an ordered array of electromagnetic beamlets,

wherein the three point sources are located at the corners of a triangle in a common plane.

2. The apparatus of claim 1, wherein said hologram has been created by directing a reference beam derived from a creation laser source at a holographic medium, deriving three additional non-collimated phase-controlled laser beams from the creation laser source, directing the three additional non-collimated phase-controlled laser beams from a common plane towards the holographic medium, said three additional non-collimated phase controlled laser beams comprising an object beam, said object and reference beams combining at the holographic medium to form an interference pattern, said interference pattern being recorded as said hologram.

3. The apparatus of claim 2, wherein, during creation of the hologram, the reference beam and the three additional non-collimated phase-controlled laser beams are derived from the creation laser source by means comprising at least two beamsplitters and a mirror.

4. The apparatus of claim 2, wherein, during creation of the hologram, the reference beam and the three non-collimated phase-controlled laser beams are derived from the creation laser source by means comprising at least two fiber-optic beamsplitters.

5. The apparatus of claim 2, wherein the wavelength of the reconstruction laser source is the same as the wavelength of the creation laser source.

6. The apparatus of claim 2, wherein the wavelength of the reconstruction laser source is different from the wavelength of the creation laser source.

7. The apparatus of claim 1, wherein the means for directing the reconstruction laser beam at the hologram comprises an optical fiber.

8. The apparatus of claim 1, wherein the hologram is generated by a computer.

9. The apparatus of claim 8, wherein the hologram is calculated from the interference of a first beam from a first source having a first wavelength and a second beam from a second source also having the first wavelength, said second beam comprising three phase-controlled beams, and the wavelength of the reconstruction source is the same as the first wavelength.

10. The apparatus of claim 8, wherein the hologram is calculated from the interference of a first beam from a first source having a first wavelength and a second beam from a second source also having the first wavelength, said second beam comprising three phase-controlled beams, and the wavelength of the reconstruction source is different from the first wavelength.

11. The apparatus of claim 1, further comprising a spatial light modulator, said spatial light modulator positioned to modulate the beams in the ordered array of electromagnetic beamlets.

12. A method for generating an array of electromagnetic beamlets comprising:

(a) directing a reference beam derived from a creation source at a holographic medium, said reference beam having a first orientation with respect to the holographic medium;

(b) deriving three additional phase-controlled beams from the creation source;

(c) directing the three additional phase-controlled beams towards the holographic medium, said three additional phase-controlled beams comprising an object beam, said object and reference beams combining at the holographic medium to form an interference pattern, said interference pattern being recorded as a hologram;

(d) directing a reconstruction beam derived from a reconstruction source at the hologram; and

(e) aligning the reconstruction beam such that it has the first orientation with respect to the hologram, thus generating three phase-controlled beams from the hologram, said phase-controlled beams overlapping each other and interfering with each other to produce the array of electromagnetic beams, wherein the three point sources are located at the corners of a triangle in a common plane.

13. The method of claim 12, wherein the reconstruction beam is a laser beam directed at the hologram using an optical fiber.

14. The method of claim 12, wherein the reference beam and the three phase-controlled beams are laser beams derived from the creation source using at least one beamsplitter and a mirror.

15. The method of claim 12, wherein the reference beam and the three additional phase-controlled beams are laser beams derived from the creation source using at least two fiber-optic beamsplitters.

16. The method of claim 12, also comprising selecting the reconstruction source such that the wavelength of the reconstruction source is the same as the wavelength of the creation source.

17. The method of claim 12, also comprising selecting the reconstruction source such that the wavelength of the reconstruction source is different from the wavelength of the creation source.

18. The method of claim 12, further comprising modulating the array of beamlets using a spatial light modulator.

19. A three-dimensional imaging system comprising:

(a) a hologram having a virtual image of a plurality of phase-controlled point sources;

(b) a laser reconstruction source producing a reconstruction beam;

(c) means for directing the reconstruction beam towards the hologram;

(d) means for aligning the reconstruction beam with respect to the hologram such that the plurality of phase controlled beams is generated, said beams overlapping each other and interfering with each other produce an array of laser beamlets originating from the at least two sources is formed;

(e) means for directing the array of laser beamlets along a first optical axis to a spatial light modulator;

(f) means for modulating the laser beamlets in at least one spatial light modulator pattern and for directing the modulated laser beamlets at an object;

(g) a video camera directed along a second optical axis at the object, wherein said second optical axis is not parallel to the first optical axis, said video camera recording a sequence of images of the array of laser beamlets reflected by the object ordered according to the sequence of spatial light modulator patterns; and

(h) means for calculating a three dimensional image of the object from the sequence of images of the array of laser beamlets.

20. The imaging system of claim 19, wherein the means for modulating the laser beamlets comprises means for modulating the laser beamlets in an ordered binary sequence.

21. The imaging system of claim 19, wherein the hologram was created by directing a reference beam derived from a creation laser source at a holographic medium, deriving at least two phase-controlled additional laser beams from the creation laser source, directing the at least two additional phase-controlled laser beams from a common plane at the holographic medium, said at least two additional phase-controlled laser beams comprising an object beam, said object and reference beams combining at the holographic medium to form an interference pattern, said interference pattern being recorded as the hologram.

22. The imaging system of claim 21, wherein the wavelength of the creation laser source is the same as the wavelength of the reconstruction laser source.

23. The imaging system of claim 21, wherein the wavelength of the creation laser source is different from the wavelength of the reconstruction laser source.

24. The imaging system of claim 21, wherein the means for directing the reconstruction laser beam at the hologram comprises a optical fiber.

25. The imaging system of claim 21, wherein the at least two additional phase-controlled laser beams are derived from the creation laser source by means comprising fiber-optic beamsplitters.

26. The imaging system of claim 21, wherein the at least two additional phase-controlled laser beams are derived from the creation laser source by means comprising optical fibers and beamsplitters.

27. The imaging system of claim 21, wherein the at least two phase-controlled point sources are three phase-controlled point sources located at the corners of a triangle in the common plane.

28. The imaging system of claim 19, wherein the at least two phase-controlled point sources are four phase-controlled point sources located at the corners of a rectangle in the common plane.

29. The imaging system of claim 19, wherein the hologram is generated by a computer.

30. A three-dimensional imaging system comprising:

(a) a hologram having a virtual image of a plurality of phase-controlled point sources;

(b) a reconstruction laser source producing a reconstruction beam;

(c) means for directing the reconstruction laser beam at the hologram;

(d) means for aligning the reconstruction beam with respect to the hologram such that the plurality of phase controlled beams are produced, said beams overlapping each other and interfering with each other to produce an array of laser beamlets;

(e) means for directing the array of laser beamlets along a first optical axis at an object;

(f) a video camera directed along a second optical axis at the object, wherein said second optical axis is not parallel to the first optical axis, said video camera comprising means for recording at least one coded image of the array of laser beamlets reflected by the object; and

(g) means for calculating a three dimensional image of the object from the at least one coded image of the array of laser beamlets reflected by the object.

31. The three dimensional imaging system of claim 30, wherein the hologram is created using means comprising optical fibers.

32. The three dimensional imaging system of claim 30, wherein the hologram was created by directing a spatially coded reference beam derived from a creation laser source at a holographic medium, deriving the plurality of additional phase-controlled laser beams from the creation laser source, directing the plurality of additional phase-controlled laser beams from a common plane at a coded spatial light modulator and then at the holographic medium, said plurality of additional phase-controlled laser beams comprising an object beam coded by the coded spatial light modulator, said coded object beam and coded reference beam combining at the holographic medium to form an interference pattern, said interference pattern being recorded as the hologram.

33. The three dimensional imaging system of claim 32, wherein the wavelength of the reconstruction laser source is the same as the wavelength of the creation laser source.

34. The three dimensional imaging system of claim 32, wherein the wavelength of the reconstruction laser source is different from the wavelength of the creation laser source.

35. The three dimensional imaging system of claim 32, wherein the plurality of additional phase-controlled laser beams are derived from the creation laser source, by means comprising optical fibers.

36. The three dimensional imaging system of claim 30, wherein the hologram comprises a virtual image of three phase-controlled point sources located at the corners of a triangle in the common plane.

37. The three dimensional imaging system of claim 36, wherein the hologram comprises a virtual image of four point phase-controlled point sources located at the corners of a rectangle in the common plane.

38. The three dimensional imaging system of claim 30, wherein the hologram is generated by a computer.

39. A method for obtaining a three dimensional image of an object comprising:

(a) directing a reference beam derived from a creation laser source at a holographic medium;

(b) deriving a first plurality of at least two additional phase-controlled beams from the creation laser source;

(c) directing the first plurality of additional phase-controlled beams at the holographic medium from a common plane, said first plurality of additional phase-controlled beams combining with the reference beam at the holographic medium to form a hologram comprising a virtual image of the first plurality of phase-controlled point sources;

(d) directing a reconstruction beam from a reconstruction laser source at the hologram comprising a virtual image of the first plurality of phase-controlled point sources, said reconstruction beam having the same orientation relative to the hologram as the reference beam had relative to the holographic medium, thereby generating a first plurality of phase-controlled laser beams, said phase controlled laser beams overlapping with each other and interfering with each other to produce an array of laser beamlets;

(e) directing the array of laser beamlets at a spatial light modulator, and then directing the array of laser beamlets along a first optical axis at an object;

(f) directing a video camera along a second optical axis at the object, said second optical axis being non-parallel to the first optical axis;

(g) recording at least one image of the reflection of the array of laser beamlets; and

(h) calculating a three dimensional image of the object from the at least one image.

40. The method of claim 39, wherein step (e) further comprises spatially modulating the array of laser beamlets to produce a coded array of laser beamlets, and step (g) comprises recording at least one coded image of the reflection of the array of laser beamlets.

41. The method of claim 40, wherein the array of laser beamlets is modulated by the spatial light modulator in an ordered binary sequence of spatial light modulator patterns.

42. The method of claim 39, wherein the first plurality of at least two additional beams is derived from the creation laser source by means comprising optical fibers.

43. The method of claim 39, wherein the first plurality of at least two additional phase-controlled beams is derived from the creation laser source by means comprising optical fiber beamsplitters.

44. The method of claim 39, wherein the first plurality is three, and the three additional phase-controlled beams are directed at the holographic medium from the corners of a triangle in the common plane.

45. The method of claim 39, wherein the first plurality is four, and the four additional phase-controlled beams are directed at the holographic medium from the corners of a rectangle in the common plane.

46. The method of claim 39, wherein the wavelength of the construction laser source is the same wavelength as the wavelength of the creation laser source.

47. The method of claim 39, wherein the wavelength of the reconstruction laser source is different from the wavelength of the creation laser source.

48. A method for obtaining a three dimensional image of an object comprising:

(a) directing a spatially coded reference beam derived from a creation laser source at a holographic medium;

(b) deriving a first plurality of at least two additional phase-controlled beams from the creation laser source;

(c) coding the first plurality of at least two additional phase-controlled beams;

(d) directing the first plurality of coded additional phase-controlled beams at the holographic medium from a common plane, said first plurality of coded additional phase-controlled beams combining with the coded reference beam at the holographic medium to form a hologram comprising a coded image of the first plurality of point sources;

(e) directing a reconstruction beam from a reconstruction laser source at the hologram comprising a coded image of the first plurality of point sources, said reconstruction beam having the same orientation relative to the hologram as the reference beam had relative to the holographic medium, thereby generating the first plurality of phase-controlled_beams, said phase-controlled beams overlapping with and interfering with each other to produce a coded array of laser beamlets;

(f) directing the coded array of laser beamlets along a first optical axis at an object;

(g) directing a video camera along a second optical axis at the object, said second optical axis being non-parallel to said first optical axis;

(h) recording at least one coded image of the reflection of the coded array of laser beamlets; and

(i) calculating a three dimensional image of the object from the at least one coded image.

49. The method of claim 48, wherein the reference beam and the first plurality of at least two additional phase-controlled beams are coded in an ordered binary sequence.

50. The method of claim 48, wherein the reference beam and the first plurality of at least two additional phase-controlled beams are derived from the creation laser source by means comprising optical fiber beamsplitters.

51. The method of claim 48, wherein the reference beam and the first plurality of at least two phase-controlled additional beams are derived from the creation laser source by means comprising optical fibers.

52. The method of claim 48, wherein the first plurality is three, and the three additional phase-controlled beams are directed at the holographic medium from the corners of a triangle in the common plane.

53. The method of claim 54, wherein the first plurality is four, and the four additional phase-controlled beams are directed at the holographic medium from the corners of a rectangle in the common plane.

54. The method of claim 48, wherein the wavelength of the reconstruction laser source is the same wavelength as the wavelength of the creation laser source.

55. The method of claim 48, wherein the wavelength of the reconstruction laser source is different from the wavelength of the creation laser source.

56. A method for generating an array of electromagnetic beamlets comprising:

(a) calculating a holographic pattern on a computer, said holographic pattern being calculated from the interference of a first source having a first wavelength and a second source also having the first wavelength, said second source consisting of three phase-controlled beams having the first wavelength;

(b) fabricating a hologram by exposing a recording medium to the holographic pattern;

(c) directing a reconstruction electromagnetic beam derived from a reconstruction source at the hologram; and

(d) aligning the reconstruction beam such that it has the first orientation with respect to the hologram, and generating three phase-controlled electromagnetic beams, said phase-controlled electromagnetic beams overlapping with each other and interfering with each other to produce an array of electromagnetic beamlets,

wherein the three point sources are located at the corners of a triangle in a common plane.

57. The method of claim 56, wherein the wavelength of the reconstruction source is different from the first wavelength.

58. The method of claim 56, wherein the wavelength of the reconstruction source is the same as the first wavelength.

59. An apparatus for generating an array of electromagnetic beamlets comprising:

(a) a hologram having an image of four phase-controlled point sources;

(b) a reconstruction electromagnetic source producing a reconstruction beam;

(c) means for directing the reconstruction beam at the hologram; and

(d) means for aligning the reconstruction beam such that four phase-controlled beams are generated from the virtual image of the four phase-controlled point sources, said first plurality of phase-controlled beams overlapping each other and interfering with each other to produce an ordered array of electromagnetic beamlets, wherein the four point sources are located at the corners of a rectangle in a common plane.

60. The apparatus of claim 59, wherein said hologram has been created by directing a reference beam derived from a creation laser source at a holographic medium, deriving four additional non-collimated phase-controlled laser beams from the creation laser source, directing the four additional non-collimated phase-controlled laser beams from a common plane towards the holographic medium, said four additional non-collimated phase-controlled laser beams comprising an object beam, said object and reference beams combining at the holographic medium to form an interference pattern, said interference pattern being recorded as said hologram.

61. The apparatus of claim 60, wherein, during creation of the hologram, the reference beam and the four additional non-collimated phase-controlled laser beams are derived from the creation laser source by means comprising at least two beamsplitters and a mirror.

62. The apparatus of claim 60, wherein, during creation of the hologram, the reference beam and the four additional non-collimated phase-controlled laser beams are derived from the creation laser source by means comprising at least two fiber-optic beamsplitters.

63. The apparatus of claim 60, wherein the wavelength of the reconstruction laser source is the same as the wavelength of the creation laser source.

64. The apparatus of claim 60, wherein the wavelength of the reconstruction source is different from the wavelength of the creation laser source.

65. The apparatus of claim 59, wherein the means for directing the reconstruction laser beam at the hologram comprises an optical fiber.

66. The apparatus of claim 59, wherein the hologram is generated by a computer.

67. The apparatus of claim 66, wherein the hologram is calculated from the interference of a first beam from a first source having a first wavelength and a second beam from a second source also having the first wavelength, said second beam comprising four phase-controlled beams, and wherein the wavelength of the reconstruction source is the same as the first wavelength.

68. The apparatus of claim 66, wherein the hologram is calculated from the interference of a first beam from a first source having a first wavelength and a second beam from a second source also having the first wavelength, said second beam comprising four phase-controlled beams, and wherein the wavelength of the reconstruction source is different from the first wavelength.

69. An apparatus for generating an array of electromagnetic beamlets comprising:

(a) a hologram having an image of a first plurality of at least two phase-controlled point sources;

(b) a reconstruction electromagnetic source producing a reconstruction beam;

(c) means for directing the reconstruction beam at the hologram; and

(d) means for aligning the reconstruction beam such that a first plurality of phase-controlled beams is generated from the virtual image of the first plurality of at least two phase-controlled point sources, said first plurality of phase-controlled beams overlapping each other and interfering with each other to produce an ordered array of electromagnetic beamlets; and

(e) a spatial light modulator, said spatial light modulator positioned to modulate the beams in the ordered array of electromagnetic beamlets.

70. The apparatus of claim 69, wherein said hologram has been created by directing a reference beam derived from a creation laser source at a holographic medium, deriving a first plurality of additional non-collimated phase-controlled laser beams from the creation laser source, directing the first plurality of additional non-collimated phase-controlled laser beams from a common plane towards the holographic medium, said first plurality of additional non-collimated phase-controlled laser beams comprising an object beam, said object and reference beams combining at the holographic medium to form an interference pattern, said interference pattern being recorded as said hologram.

71. The apparatus of claim 70, wherein, during creation of the hologram, the reference beam and the first plurality of additional non-collimated phase-controlled laser beams are derived from the creation laser source by means comprising at least two beamsplitters and a mirror.

72. The apparatus of claim 70, wherein, during creation of the hologram, the reference beam and the first plurality of additional non-collimated phase-controlled laser beams are derived from the creation laser source by means comprising at least two fiber-optic beamsplitters.

73. The apparatus of claim 70, wherein the wavelength of the reconstruction laser source is the same as the wavelength of the creation laser source.

74. The apparatus of claim 70, wherein the wavelength of the reconstruction laser source is different from the wavelength of the creation laser source.

75. The apparatus of claim 69, wherein the means for directing the reconstruction laser beam at the hologram comprises an optical fiber.

76. The apparatus of claim 69, wherein the hologram is generated by a computer.

77. The apparatus of claim 76, wherein the hologram is calculated from the interference of a first beam from a first source having a first wavelength and a second beam from a second source also having the first wavelength, said second beam comprising a first plurality of at least two phase-controlled beams, and the wavelength of the reconstruction source is the same as the first wavelength.

78. The apparatus of claim 76, wherein the hologram is calculated from the interference of a first beam from a first source having a first wavelength and a second beam from a second source also having the first wavelength, said second beam comprising a first plurality of at least two phase-controlled beams, and the wavelength of the reconstruction source is different from the first wavelength.

79. A method for generating an array of electromagnetic beamlets comprising:

(a) directing a reference beam derived from a creation source at a holographic medium, said reference beam having a first orientation with respect to the holographic medium;

(b) deriving four additional phase-controlled beams from the creation source;

(c) directing the four additional phase-controlled beams towards the holographic medium, said four additional phase-controlled beams comprising an object beam, said object and reference beams combining at the holographic medium to form an interference pattern, said interference pattern being recorded as a hologram;

(d) directing a reconstruction beam derived from a reconstruction source at the hologram; and

(e) aligning the reconstruction beam such that it has the first orientation with respect to the hologram, thus generating four phase-controlled beams from the hologram, said phase-controlled beams overlapping each other and interfering with each other to produce the array of electromagnetic beams, wherein the four additional laser beams originate from the four corners of a rectangle in a common plane.

80. The method of claim 79, wherein the reconstruction beam is a laser beam directed at the hologram using an optical fiber.

81. The method of claim 79, wherein the reference beam and the four additional phase-controlled beams are laser beams derived from the creation source using at least one beamsplitter and a mirror.

82. The method of claim 79, wherein the reference beam and the four additional phase-controlled beams are laser beams derived from the creation source using at least two fiber-optic beamsplitters.

83. The method of claim 79, also comprising selecting the reconstruction source such that the wavelength of the reconstruction source is the same as the wavelength of the creation source.

84. The method of claim 79, also comprising selecting the reconstruction source such that the wavelength of the reconstruction source is different from the wavelength of the creation source.

85. A method for generating an array of electromagnetic beamlets comprising:

(a) directing a reference beam derived from a creation source at a holographic medium, said reference beam having a first orientation with respect to the holographic medium;

(b) deriving a first plurality of at least two additional phase-controlled beams from the creation source;

(c) directing the first plurality of additional beams phase-controlled towards the holographic medium, said first plurality of additional phase-controlled beams comprising an object beam, said object and reference beams combining at the holographic medium to form an interference pattern, said interference pattern being recorded as a hologram;

(d) directing a reconstruction beam derived from a reconstruction source at the hologram; and

(e) aligning the reconstruction beam such that it has the first orientation with respect to the hologram, thus generating a first plurality of phase-controlled beams from the hologram, said phase-controlled beams overlapping each other and interfering with each other to produce the array of electromagnetic beams; and

(f) modulating the array of beamlets using a spatial light modulator.

86. The method of claim 85, wherein the reconstruction beam is a laser beam directed at the hologram using an optical fiber.

87. The method of claim 85, wherein the reference beam and the first plurality of additional phase-controlled beams are laser beams derived from the creation source using at least one beamsplitters and a mirror.

88. The method of claim 85, wherein the reference beam and the first plurality of additional phase-controlled beams are laser beams derived from the creation source using at least two fiber-optic beamsplitters.

89. The method of claim 85, also comprising selecting the reconstruction source such that the wavelength of the reconstruction source is the same as the wavelength of the creation source.

90. The method of claim 85, also comprising selecting the reconstruction source such that the wavelength of the reconstruction source is different from the wavelength of the creation source.

91. A method for generating an array of electromagnetic beamlets comprising:

(a) calculating a holographic pattern on a computer, said holographic pattern being calculated from the interference of a first source having a first wavelength and a second source also having the first wavelength, said second source consisting of four phase-controlled beams having the first wavelength;

(b) fabricating a hologram by exposing a recording medium to the holographic pattern;

(c) directing a reconstruction electromagnetic beam derived from a reconstruction source at the hologram; and

(d) aligning the reconstruction beam such that it has the first orientation with respect to the hologram, and generating the four phase-controlled electromagnetic beams, said phase-controlled electromagnetic beams overlapping with each other and interfering with each other to produce an array of electromagnetic beamlets,

wherein the four point sources are located at the corners of a rectangle in a common plane.

92. The method of claim 91, wherein the wavelength of the reconstruction source is different from the first wavelength.

93. The method of claim 91, wherein the wavelength of the reconstruction source is the same as the first wavelength.