Method and apparatus for multiwavelength imaging spectrometer

• US 7,012,695 B2
• Filed: 07/19/2004
• Issued: 03/14/2006
• Est. Priority Date: 07/18/2003
• Status: Active Grant

• Current Assignee: Chemimage Corporation
• Original Assignee: Chemimage Corporation
• Inventors: Wang, Chenhui, Treado, Patrick J., Maier, John S.
• Primary Examiner(s): Toatley, Jr., Gregory J.
• Assistant Examiner(s): Lyons, Michael A.
• Application Number:
  US10/893,332
• Publication Number:
  US 20050030657A1
• Time in Patent Office: 603 Days
• Field of Search: 356/416, 356/419, 356/453, 356/454, 356/519, 359/577, 359/578, 359/885, 349/19, 349/33, 349/193, 349/198
• US Class Current: 356/453
• CPC Class Codes: G01J 3/02 Details
• CPC Class Codes: G01J 3/0224 using polarising or depolarising elements
• CPC Class Codes: G01J 3/0229 using masks, aperture plates, spatial light modulators or spatial filters, e.g. reflective filters
• CPC Class Codes: G01J 3/0256 Compact construction
• CPC Class Codes: G01J 3/0264 Electrical interface; User interface
• CPC Class Codes: G01J 3/0272 Handheld
• CPC Class Codes: G01J 3/0283 using a charging unit
• CPC Class Codes: G01J 3/10 Arrangements of light sources specially adapted for spectrometry or colorimetry
• CPC Class Codes: G01J 3/44 Raman spectrometry; Scattering spectrometry ; Fluorescence spectrometry
• CPC Class Codes: G01J 3/4406 Fluorescence spectrometry
• CPC Class Codes: G01N 2021/6417 Spectrofluorimetric devices
• CPC Class Codes: G01N 2021/6423 Spectral mapping, video display
• CPC Class Codes: G01N 2021/6471 Special filters, filter wheel
• CPC Class Codes: G01N 21/6456 Spatial resolved fluorescence measurements; Imaging
• CPC Class Codes: G01N 21/65 Raman scattering
• CPC Class Codes: G01N 2201/0221 Portable; cableless; compact; hand-held
• CPC Class Codes: G01N 2201/0627 Use of several LED's for spectral resolution
• CPC Class Codes: G02F 1/133371 Cells with varying thickness of the liquid crystal layer
• CPC Class Codes: G02F 1/1347 Arrangement of liquid crystal layers or cells in which the final condition of one light beam is achieved by the addition of the effects of two or more layers or cells

Abstract

The disclosure generally relates to a method and apparatus for multi-wavelength imaging spectrometer. More specifically, in one embodiment, the disclosure relates to an optical filter for passing photons therethrough. The filter includes a first filter stage and a second filter stage. The first filter stage may include a first retarder element and a first liquid crystal cell. The first element may include an input face and an output face. One of the first element faces is not oriented substantially normal to the trajectory of photons passing through the filter.

Claims

1. In an optical filter comprising plural filter stages where a first one of the plural stages includes a retarder element and a liquid crystal cell each of which have a uniform thickness, the improvement of replacing the first one stage with a second one stage having a retarder element and a liquid crystal cell where either the element or the cell does not have a uniform thickness.

2. The filter of claim 1 wherein the element and the cell of the first one stage have the same thickness.

3. The filter of claim 1 wherein the element of the second one stage does not have a uniform thickness.

4. The filter of claim 1 wherein the element of the second one stage is wedge-shaped.

5. The filter of claim 1 wherein the element of the second one stage has a stepped-wedge shape.

6. In an optical filter comprising plural filter stages where a first one of the plural stages includes a retarder element and a liquid crystal cell each of which have a uniform thickness, the improvement of replacing the first one stage with a second one stage having a retarder element and a liquid crystal cell where the cell comprises:

a pixelized liquid crystal structure for filtering photons;

a voltage source operably connected to said pixelized liquid crystal structure; and

means for controlling the amount of voltage applied by said voltage source to ones of the pixels;

wherein the liquid crystal is substantially uniformly thick in the direction of photon travel therethrough.

7. In an optical filter comprising plural filter stages where a first one of the plural stages includes a retarder element and a liquid crystal cell each of which have a uniform thickness, the improvement of replacing the first one stage with a second one stage having a retarder element and a liquid crystal cell where the cell comprises:

a columnized liquid crystal structure for filtering photons;

a voltage source operably connected to said columnized liquid crystal structure; and

means for controlling the amount of voltage applied by said voltage source to ones of said columns;

wherein the liquid crystal is substantially uniformly thick in the direction of photon travel therethrough.

8. An optical filter comprising:

a first filter stage comprising a first retarder element and a first liquid crystal cell; and

a second filter stage,

wherein either the first element or the first cell do not have a uniform thickness.

9. The filter of claim 8 wherein said second stage comprises a second retarder element having a first uniform thickness and a second liquid crystal cell having a second uniform thickness.

10. The filter of claim 9 wherein the first uniform thickness and the second uniform thickness are substantially the same.

11. The filter of claim 8 wherein the first element does not have a uniform thickness.

12. The filter of claim 11 wherein the first element is wedge-shaped.

13. The filter of claim 11 wherein the first element has a stepped-wedge shape.

14. The filter of claim 8 wherein the first and second stages comprise a birefringence interference filter.

15. The filter of claim 8 wherein the first and second stages comprise an Evans split element filter.

16. The filter of claim 8 wherein the first and second stages comprise a Solc filter.

17. The filter of claim 8 wherein the first and second stages comprise a Lyot filter.

18. The filter of claim 17 including an Evans split element filter.

19. The filter of claim 8 wherein said first element is comprised of quartz.

20. The filter of claim 8 wherein said first element is comprised of lithium niobate.

21. The filter of claim 8 wherein the filter is a tunable filter.

22. The filter of claim 8 wherein the filter includes a polarizer.

23. The filter of claim 8 wherein the filter is pixelized.

24. The filter of claim 8 wherein the filter is columnized.

25. The filter of claim 8, wherein the first and the second filter stages define a hybrid filter.

26. The filter of claim 8, wherein at least one of the first and the second stage is selected from a group consisting of a Lyot filter, an Evans filter, a Fabry-Perot filter and a Solc filter and the combination of the first and the second stage defines a hybrid filter.

27. A method of manufacturing an optical filter comprising the steps of:

providing a first filter stage comprising a first retarder element and a first liquid crystal cell wherein either the first element or the first cell do not have a uniform thickness;

providing a second filter stage; and

aligning the first filter stage with the second filter stage.

28. The method of claim 27 wherein the first and second stages comprise a Lyot filter and including the steps of:

providing an Evans split element filter; and

aligning the Evans split element filter with the Lyot filter.

29. The method of claim 27 wherein the first and second stages comprise a Lyot filter and including the steps of:

providing a Fabry-Perot filter; and

aligning the Fabry-Perot filter with the Lyot filter.

30. The method of claim 27 wherein the first and second stages comprise a Lyot filter and including the steps of:

providing a Solc filter; and

aligning the Solc filter with the Lyot filter.

31. The method of claim 27, wherein the optical filter is a hybrid filter and at least one of the first or the second stage is selected from the group consisting of a Lyot filter, an Evans Filter, a Solc filter and a Fabry-Perot filter.

32. An optical filter for passing photons therethrough, the filter comprising:

a first filter stage comprising a first retarder element and a first liquid crystal cell; and

a second filter stage,

wherein said first element comprises an input face and an output face, and

wherein one of said first element faces is not oriented substantially normal to the trajectory of photons passing through the filter.

33. The filter of claim 32 wherein said second stage comprises a second retarder element having a first uniform thickness and a second liquid crystal cell having a second uniform thickness.

34. The filter of claim 33 wherein the first uniform thickness and the second uniform thickness are substantially the same.

35. The filter of claim 32 wherein the first element is wedge-shaped.

36. The filter of claim 32 wherein the first element has a stepped-wedge shape.

37. The filter of claim 32 wherein the first and second stages comprise a birefringence interference filter.

38. The filter of claim 32 wherein the first and second stages comprise an Evans split element filter.

39. The filter of claim 32 wherein the first and second stages comprise a Solc filter.

40. The filter of claim 32 wherein the first and second stages comprise a Lyot filter.

41. The filter of claim 40 including an Evans split element filter.

42. The filter of claim 32 wherein said first element is comprised of quartz.

43. The filter of claim 32 wherein said first element is comprised of lithium niobate.

44. The filter of claim 32 wherein the filter is a tunable filter.

45. The filter of claim 32 wherein the filter includes a polarizer.

46. The filter of claim 32 wherein the filter is pixelized.

47. The filter of claim 32 wherein the filter is columnized.

48. An optical filter comprising:

a first filter stage comprising a first retarder element and a first liquid crystal cell; and

a second filter stage,

wherein said first element comprises an input face and an output face, and

wherein said first element faces are not oriented substantially parallel to each other.

49. The filter of claim 48 wherein said second stage comprises a second retarder element having a first uniform thickness and a second liquid crystal cell having a second uniform thickness.

50. The filter of claim 49 wherein the first uniform thickness and the second uniform thickness are substantially the same.

51. The filter of claim 48 wherein the first element is wedge-shaped.

52. The filter of claim 48 wherein the first element has a stepped-wedge shape.

53. The filter of claim 48 wherein the first and second stages comprise a birefringence interference filter.

54. The filter of claim 48 wherein the first and second stages comprise an Evans split element filter.

55. The filter of claim 48 wherein the first and second stages comprise a Solc filter.

56. The filter of claim 48 wherein the first and second stages comprise a Lyot filter.

57. The filter of claim 48 including an Evans split element filter.

58. The filter of claim 48 wherein said first element is comprised of quartz.

59. The filter of claim 48 wherein said first element is comprised of lithium niobate.

60. The filter of claim 48 wherein the filter is a tunable filter.

61. The filter of claim 48 wherein the filter includes a polarizer.

62. The filter of claim 48 wherein the filter is pixelized.

63. The filter of claim 48 wherein the filter is columnized.

64. The filter of claim 48, wherein the optical filter is a hybrid filter and at least one of the first or the second stage is selected from the group consisting of a Lyot filter, an Evans Filter, a Solc filter and a Fabry-Perot filter.

65. A system for obtaining a spectrum of a sample, comprising:

a photon emission source for illuminating the sample with a plurality of photons to thereby produce photons scattered by the sample;

an optical lens for collecting the scattered photons;

a filter for receiving the collected scattered photons and providing therefrom filtered photons; and

a photon detector for receiving the filtered photons and obtaining therefrom a spectrum of the sample,

wherein said filter comprises;

a first filter stage comprising a first retarder element and a first liquid crystal cell; and

a second filter stage,

wherein either the first element or the first cell do not have a uniform thickness.

66. The system of claim 65 wherein said second stage comprises a second retarder element having a first uniform thickness and a second liquid crystal cell having a second uniform thickness.

67. The system of claim 66 wherein the first uniform thickness and the second uniform thickness are substantially the same.

68. The system of claim 65 wherein the first element does not have a uniform thickness.

69. The system of claim 68 wherein the first element is wedge-shaped.

70. The system of claim 68 wherein the first element has a stepped-wedge shape.

71. The system of claim 65 wherein the first and second stages comprise a birefringence interference filter.

72. The system of claim 65 wherein the first and second stages comprise an Evans split element filter.

73. The system of claim 65 wherein the first and second stages comprise a Solc filter.

74. The system of claim 65 wherein the first and second stages comprise a Lyot filter.

75. The system of claim 74 including an Evans split element filter.

76. The system of claim 65 wherein said first element is comprised of quartz.

77. The system of claim 65 wherein said first element is comprised of lithium niobate.

78. The system of claim 65 wherein the filter is a tunable filter.

79. The system of claim 65 wherein the filter includes a polarizer.

80. The system of claim 65 wherein the filter is pixelized.

81. The system of claim 65 wherein the filter is columnized.

82. The system of claim 65 wherein said photon detector is selected from the group consisting of:

charge-coupled device, complementary metal oxide semiconductor, charge injection device, intensified charge injection device, electron multiplying charge-coupled device, silicon photo diode, silicon avalanche diode, and focal plane array.

83. The system of claim 65 wherein said photon emission source is a laser.

84. The system of claim 65 wherein said photon emission source is a light emitting diode.

85. The system of claim 84 wherein said light emitting diode is disposed as a ring.

86. The system of claim 85 wherein said light emitting diode is a plurality of light emitting diodes.

87. The system of claim 84 wherein said light emitting diode is a plurality of light emitting diodes wherein one of said plural light emitting diodes emits photons at a wavelength that is different than a wavelength of photons emitted by another of said plural light emitting diodes.

88. The system of claim 87 wherein the wavelength of photons emitted by one of said plural light emitting diodes is in the ultraviolet wavelength range.

89. The system of claim 87 wherein the wavelength of photons emitted by one of said plural light emitting diodes is in the near infrared wavelength range.

90. The system of claim 65 wherein said spectrum is obtained over a predetermined period of time and said sample is stationary during said predetermined period of time.

91. The system of claim 65 wherein said scattered photons include photons emitted by said sample.

92. The system of claim 65 wherein said spectrum is a Raman spectrum.

93. The system of claim 65 wherein the system is a portable system.

94. The system of claim 65 wherein the system is a hand-held system.

95. The system of claim 65 wherein said spectrum is a spatially accurate wavelength-resolved image.

96. The system of claim 65 wherein ones of said filtered photons each have a wavelength within a predetermined wavelength band.

97. The system of claim 65 wherein said first filter element includes a liquid crystal.

98. The system of claim 65 wherein said retarder element is comprised of quartz.

99. The system of claim 65 wherein said retarder element is comprised of lithium niobate.

100. The system of claim 65, wherein the filter is a hybrid filter and at least one of the first or the second filter stage is selected from the group consisting of a Lyot filter, an Evans Filter, a Solc filter and a Fabry-Perot filter.

101. A method for obtaining a spectrum of a sample, comprising:

providing a sample;

illuminating the sample with a plurality of photons to thereby produce photons scattered by the sample;

collecting the scattered photons;

receiving the collected scattered photons with a filter and providing therefrom filtered photons; and

receiving the filtered photons and obtaining therefrom a spectrum of the sample,

wherein said filter comprises;

a first filter stage comprising a first retarder element and a first liquid crystal cell; and

a second filter stage,

wherein either the first element or the first cell do not have a uniform thickness.

102. The method of claim 101 wherein the first and second stages comprise a Lyot filter and including the steps of:

providing an Evans split element filter; and

aligning the Evans split element filter with the Lyot filter.

103. The method of claim 101 wherein the first and second stages comprise a Lyot filter and including the steps of:

providing a Fabry-Perot filter; and

aligning the Fabry-Perot filter with the Lyot filter.

104. The method of claim 101 wherein the first and second stages comprise a Lyot filter and including the steps of:

providing a Solc filter; and

aligning the Solc filter with the Lyot filter.

105. The method of claim 101, wherein the optical filter is a hybrid filter and at least one of the first or the second stage is selected from the group consisting of a Lyot filter, an Evans Filter, a Solc filter and a Fabry-Perot filter.

106. An optical filter comprising:

a first liquid crystal cell comprising a first region having a first photon retardation value and a second region having a second photon retardation value;

a second liquid crystal cell comprising a first region having said first photon retardation value and a second region having said second photon retardation value;

wherein each of the first and the second retardation values are defined by a first excitation source and a second excitation source communicating respectively with each of the first and the second regions of said first and the second cells.

107. The optical filter of claim 106 wherein the first region of the first cell is substantially aligned with the first region of the second cell.

108. The optical filter of claim 106 wherein the first cell and the second cell form one of a Lyot filter, an Evans split element filter, a Solc filter, or a hybrid filter.

109. An optical filter comprising:

a pixelized liquid crystal stage for filtering photons;

a voltage source operably connected to the liquid crystal pixels; and

means for controlling the amount of voltage applied by said voltage source to ones of said pixels;

wherein the liquid crystal is substantially uniformly thick in the direction of photon travel therethrough.

110. The optical filter of claim 109 wherein the amount of voltage applied to a first set of ones of said pixels is substantially the same.

111. The optical filter of claim 109 wherein the amount of voltage applied to each of said pixels is substantially the same.

112. An optical filter comprising:

a columnized liquid crystal stage for filtering photons;

a voltage source operably connected to the liquid crystal columns; and

means for controlling the amount of voltage applied by said voltage source to ones of said columns;

wherein the liquid crystal is substantially uniformly thick in the direction of photon travel therethrough.

113. The optical filter of claim 112 wherein the amount of voltage applied to a first set of ones of said columns is substantially the same.

114. The optical filter of claim 112 wherein the amount of voltage applied to each of said columns is substantially the same.