Rippled mixers for uniformity and color mixing

• US 7,777,955 B2
• Filed: 05/26/2006
• Issued: 08/17/2010
• Est. Priority Date: 07/29/2005
• Status: Active Grant

• Current Assignee: Synopsys Incorporated
• Original Assignee: Optical Research Associates (Synopsys Incorporated)
• Inventors: McGuire, James P. Jr., Cassarly, William J., Davenport, Thomas L. R.
• Primary Examiner(s): Stultz; Jessica T
• Assistant Examiner(s): Sahle; Mahidere S
• Application Number:
  US11/442,673
• Publication Number:
  US 20070024971A1
• Time in Patent Office: 1,544 Days
• Field of Search: 359/546, 359/618, 222/137, 222/145.6, 222/570, 366/339, 366/343, 455/226.1, 455/330, 241/46.11, 362/551, 362/555, 362/26
• US Class Current: 359/618
• CPC Class Codes: G02B 27/0994 Fibers, light pipes optical fibers per se G02B6/02
• CPC Class Codes: G02B 6/0008 the light being emitted at the end of the fibre
• CPC Class Codes: G02B 6/0018 Redirecting means on the surface of the light guide
• CPC Class Codes: G02B 6/0038 Linear indentations or grooves, e.g. arc-shaped grooves or meandering grooves, extending over the full length or width of the light guide
• CPC Class Codes: G02B 6/0068 Arrangements of plural sources, e.g. multi-colour light sources
• CPC Class Codes: G02B 6/0096 the lights guides being of the hollow type
• CPC Class Codes: G02B 6/4298 coupling with non-coherent light sources and/or radiation detectors, e.g. lamps, incandescent bulbs, scintillation chambers

Abstract

Various embodiments described herein comprise mixers comprising a light pipe having input and output ends and a central region therebetween. An optical path extends in a longitudinal direction from the input end through the central region to the output end. The central region of the light pipe comprises one or more rippled reflective sidewalls having a plurality of elongate ridges and valleys and sloping surfaces therebetween. Light from the input end propagating along the optical path reflects from the sloping surfaces and is redirected at a different azimuthal direction toward the output end thereby mixing the light at the output end. Illuminance and/or color mixing can therefore be provided.

Claims

1. An illumination system comprising:

a plurality of different light emitting diodes; and

a mixer comprising a light pipe having input and output ends and a central region therebetween, an optical path extending in a longitudinal direction from said input end through said central region to said output end, said plurality of light emitting diodes disposed in proximity to said input end wherein at least one of said light emitting diodes is offset from the center of the input end,

wherein said central region of said light pipe comprises one or more rippled sidewalls having a plurality of elongate ridges and valleys and sloping surfaces therebetween, at least one ridge or valley of said ridges and valleys at least partially formed by a faceted surface comprising three or more substantially nonorthogonal surface portions or by a rounded surface,

wherein light from said plurality of light emitting diodes propagating along said optical path reflects from said sloping surfaces and is redirected at a different azimuthal direction toward said output end thereby mixing and increasing uniformity of said light at said output end.

2. The illumination system of claim 1, wherein a portion of said ridges and valleys are formed by rounded surfaces and another portion of said ridges and valleys are formed by faceted surfaces.

3. The illumination system of claim 1, wherein said plurality of light emitting diodes comprises different color light emitting diodes.

4. The illumination system of claim 3, wherein said plurality of light emitting diodes comprises red, blue, and green light emitting diodes.

5. The illumination system of claim 1, wherein said plurality of light emitting diodes comprises a linear array.

6. The illumination system of claim 1, wherein said plurality of light emitting diodes comprises a diode array comprising a plurality of rows and columns of light emitting diodes.

7. The illumination system of claim 1, further comprising a reflective collector at said input end that receives light from said plurality of light emitting diodes and directs said light into said light pipe.

8. The illumination system of claim 7, wherein said reflective collector comprises an elliptical collector having an ellipsoidally shaped reflective surface.

9. The illumination system of claim 1, wherein said light pipe comprises a hollow light pipe with said central region being open.

10. The illumination system of claim 9, wherein said sidewalls comprise a reflective film.

11. The illumination system of claim 10, wherein said reflective film comprises metallization or a dielectric multilayer coating.

12. The illumination system of claim 1, wherein said light pipe comprises a solid light pipe and said central region comprises substantially optically transmissive material.

13. The illumination system of claim 12, wherein said central region comprises glass or plastic.

14. The illumination system of claim 1, wherein said light pipe comprises a flexible light pipe.

15. The illumination system of claim 14, wherein said light pipe comprises an optical fiber.

16. The illumination system of claim 15, wherein said optical fiber has a core diameter of least about 3 millimeters.

17. The illumination system of claim 1, wherein said light pipe comprises one or more substantially planar rippled sidewalls.

18. The illumination system of claim 1, wherein said light pipe comprises one or more substantially curved rippled sidewalls.

19. The illumination system of claim 1, wherein said light pipe comprises a right circular cylinder, said output end having a circular cross-section such that said light pipe outputs a substantially circular beam.

20. The illumination system of claim 1, wherein said light pipe comprises a right prism defined by four planar sidewalls such that said output end has a square or rectangular cross-section and said light pipe outputs a substantially square or rectangular shaped beam.

21. The illumination system of claim 1, wherein said light pipe has a width of between about 1 millimeter and about 12 millimeters.

22. The illumination system of claim 1, wherein said light pipe has a length of between about 2 millimeters and about 35 millimeters.

23. The illumination system of claim 1, wherein said sloping surfaces comprise planar surfaces.

24. The illumination system of claim 23, wherein a given sloping surface comprises a plurality of facets.

25. The illumination system of claim 1, wherein said ridges and valleys are curved.

26. The illumination system of claim 1, wherein at least one of said ridges is at least partially formed by a rounded surface.

27. The illumination system of claim 1, wherein size, shape, or spacing of the ridges or valleys varies for different ridges or valleys.

28. The illumination system of claim 1, wherein said ridges have an average spacing of between about 1 percent and about 30 percent of the width of said light pipe.

29. The illumination system of claim 1, wherein said ridges have an average spacing of between about 1 micron and about 1000 microns.

30. The illumination system of claim 1, wherein said ridges have an average height measured with respect to said valleys of between about 1 micron and about 1000 microns.

31. The illumination system of claim 1, wherein said elongate ridges have the same heights.

32. The illumination system of claim 1, wherein said elongate ridges have different heights.

33. The illumination system of claim 1, wherein said elongate ridges have an average vertex angle of between about 15 degrees and about 65 degrees.

34. The illumination of claim 1, wherein said ridges have an average angle α

of between about 10 degrees and about 65 degrees.

35. The illumination system of claim 1, wherein said ridges have an average angle α

of between about 10 degrees and about 25 degrees.

36. The illumination system of claim 1, wherein said ridges comprise vertices and at least one of said vertices of said ridges is formed by a rounded surface.

37. The illumination system of claim 36, wherein said ridges have an angle α

of between about 20 degrees and about 37 degrees.

38. The illumination system of claim 1, wherein said elongate ridges have a constant spacing therebetween.

39. The illumination system of claim 1, wherein said elongate ridges have varying spacing therebetween.

40. The illumination system of claim 1, wherein said elongate ridges have an average length of between about 50 percent and about 100 percent of the length of the light pipe.

41. The illumination system of claim 1, wherein said elongate ridges have an average length of between about 0.1 centimeters and about 10 centimeters.

42. The illumination system of claim 1, wherein said elongate ridges extend along a direction parallel to said longitudinal direction.

43. The illumination system of claim 1, wherein said elongate ridges are oriented at an oblique angle with respect to said longitudinal direction.

44. The illumination system of claim 43, wherein said angle is between about 5 degrees and about 40 degrees.

45. The illumination system of claim 1, wherein a first portion of said elongate ridges and valleys are oriented at an angle with respect to said longitudinal direction and a second portion of said elongate ridges and valleys are oriented at a different angle with respect to said longitudinal direction.

46. The illumination system of claim 1, wherein a first portion of said elongate ridges and valleys cross a second portion of said elongate ridges and valleys.

47. The illumination system of claim 1, wherein light reflects from said sloping surfaces via total internal reflection.

48. The illumination system of claim 1, wherein the illumination system comprises a flashlight.

49. The illumination system of claim 1, wherein the illumination system comprises a portable light.

50. The illumination system of claim 1, wherein light entering said input end is mixed such that the standard deviation of the illuminance distribution is reduced to less than 5 percent at said output end.

51. The illumination system of claim 1, wherein light of varying color entering said input end is mixed such that the standard deviation of the delta_u′

_v′

of the color of the light is reduced to less than 0.003 at said output end.

52. The illumination system of claim 1, wherein one or more of said ridges are asymmetrical.

83. The illumination system of claim 1, wherein at least one of said ridges or valleys is at least partially formed by a rounded surface.

94. The illumination system of claim 9, wherein said plurality of different light emitting diodes are arranged in the x direction and said light pipe has a length-to-width ratio for a width along the x direction of at least about 6:

1 and said light at said input end of said light pipe has a numerical aperture at least about 0.45.

95. The illumination system of claim 12, wherein said plurality of different light emitting diodes are arranged in the x direction and said light pipe has a length-to-width ratio for a width along the x direction of at least about 9:

1 and said light at said input end of said light pipe has a numerical aperture at least about 0.45.

97. The illumination system of claim 1, wherein said three or more substantially nonorthogonal surface portions comprise said sloping surfaces.

101. The illumination system of claim 1, wherein at least one of said valleys is at least partially formed by a rounded surface.

102. The illumination system of claim 1, wherein said central region of said mixer has a top, a bottom, and first and second sides, and a plurality of elongate ridges and valleys and sloping surfaces therebetween on at least one of said top and bottom and on at least one of said first and second sides.

53. A lighting apparatus comprising:

a light source comprising a plurality of emitters; and

a mixer comprising a solid light pipe having an input end and an output end and a central region therebetween, said mixer comprising at least one rippled surface in said central region comprising a plurality of peaks and valleys connected by sloping surface portions, said peaks and valleys each comprising a vertex at least partially formed by a rounded portion or by two or more substantially nonorthogonal surface portions, said peaks having an average angle α

of between about 10 degrees and about 65 degrees,

wherein at least one of said emitters is offset from the center of the input end, and light entering said input end propagating longitudinally along said central region is deflected by said sloping surface portions of said rippled surface in an azimuthal direction thereby increasing mixing of said light in said mixer and uniformity at said output end.

54. The lighting apparatus of claim 53, wherein said plurality of emitters comprises a plurality of light emitting diodes.

55. The lighting apparatus of claim 54, wherein said plurality of emitters comprises red, green, and blue light emitting diodes.

56. The lighting apparatus of claim 53, wherein said plurality of emitters comprises at least one emitter that emits light of a shorter wavelength and a phosphor that converts said light having said shorter wavelength into light having a longer wavelength.

57. The lighting apparatus of claim 56, wherein said plurality of emitters comprises a plurality of visible wavelength emitters and said at least one emitter that emits light of a shorter wavelength comprises a UV light emitter.

58. The lighting apparatus of claim 53, wherein said mixer comprises sidewalls defining a cavity for propagation of light therein, said at least one rippled surface being disposed within said cavity spaced apart from said sidewalls.

59. The lighting apparatus of claim 58, wherein said sidewalls comprise a reflective material.

60. The lighting apparatus of claim 58, wherein said cavity comprises substantially optically transmissive material.

61. The lighting apparatus of claim 58, wherein said at least one rippled surface is substantially transmissive.

62. The lighting apparatus of claim 53, wherein said mixer comprises a flexible light pipe.

63. The lighting apparatus of claim 53, wherein said mixer comprises an optical fiber.

64. The lighting apparatus of claim 63, wherein said optical fiber has a core diameter of at least 3 millimeters in diameter.

65. The lighting apparatus of claim 53, wherein said peaks are rounded.

66. The lighting apparatus of claim 53, wherein size, shape, or spacing of the peaks or valleys varies for different peaks or valleys.

67. The lighting apparatus of claim 53, wherein said light source comprises an incoherent light source.

68. The lighting apparatus of claim 53, wherein the lighting apparatus comprises a flashlight.

69. The lighting apparatus of claim 53, wherein the lighting apparatus comprises a portable light.

70. The lighting apparatus of claim 53, wherein light entering said input end is mixed such that the standard deviation of the illuminance distribution is reduced to less than 5 percent at said output end.

71. The lighting apparatus of claim 53, wherein light of varying color entering said input end is mixed such that the standard deviation of the delta_u′

_v′

of the color of the light is reduced to less than 0.003 at said output end.

72. The lighting apparatus of claim 53, wherein said peaks have an average apex angle of between about 15 degrees and about 65 degrees.

73. The lighting apparatus of claim 53, wherein said peaks have an average angle α

of between about 10 degrees and about 25 degrees.

74. The lighting apparatus of claim 53, wherein said vertices of said peaks are formed by round surfaces.

75. The lighting apparatus of claim 74, wherein said peaks have an angle α

of between about 20 degrees and about 37 degrees.

76. The lighting apparatus of claim 74, wherein one or more of said peaks are asymmetrical.

91. The lighting apparatus of claim 53, wherein the average angle α

is an average of a peak angle defined for each of said plurality of peaks, each peak angle defined in terms of a height of a peak and a distance between successive peaks.

96. The lighting apparatus of claim 53, wherein said plurality of emitters are arranged in the x direction and said light pipe has a length-to-width ratio for a width along the x direction of at least about 9:

1 and said light entering said input end has a numerical aperture at least about 0.45.

98. The lighting apparatus of claim 53, wherein said two or more substantially nonorthogonal surface portions comprise said sloping surface portions.

103. The lighting apparatus of claim 53, wherein said central region of said solid light pipe has a top, a bottom, and first and second sides, and a plurality of peaks and valleys connected by sloping surface portions on at least one of said top and bottom and on at least one of said first and second sides.

106. The lighting apparatus of claim 53, wherein said mixer comprises an optical path extending in a longitudinal direction from said input end through said central region to said output end, said peaks extending along a direction parallel to said longitudinal direction.

107. The lighting apparatus of claim 53, wherein said mixer comprises an optical path extending in a longitudinal direction from said input end through said central region to said output end, said peaks oriented at an oblique angle with respect to said longitudinal direction.

108. The lighting apparatus of claim 107, wherein said angle is between about 5 degrees and about 40 degrees.

77. An illumination system comprising:

a plurality of light emitting diodes; and

an elongate member having an input end and an output end and a central region therebetween, said input end having a different size or shape than said output end, and at least one of said light emitting diodes displaced from the center of the input end;

wherein said elongate member comprises at least one rippled surface in said central region comprising a plurality of peaks and valleys connected by sloping surface portions, said peaks each comprising a vertex at least partially formed by two or more substantially nonorthogonal surface portions or by a rounded surface, said peaks having an average angle α

of less than about 65 degrees, such that light entering said input end propagating longitudinally along said central region is deflected by said sloping surface portions of said rippled surface in an azimuthal direction thereby increasing mixing of said light and uniformity at said output end.

78. The illumination system of claim 77, wherein said input end has a different size than said output end.

79. The illumination system of claim 78, wherein said elongate member has a length that is sufficiently long such that etendue is substantially conserved from said input end to said output end.

80. The illumination system of claim 77, wherein said input end has a different shape than said output end.

81. The illumination system of claim 80, wherein said input end has a rectilinear shaped aperture and said output end has a curvilinear shaped aperture.

82. The illumination system of claim 80, wherein said output end comprises a curved output face having optical power.

92. The illumination system of claim 77, wherein the average angle α

is an average of a peak angle defined for each of said plurality of peaks, each peak angle defined in terms of a height of a peak and a distance between successive peaks.

93. The illumination system of claim 77, wherein said peaks have an average angle α

of between about 10 degrees and about 65 degrees.

99. The illumination system of claim 77, wherein said two or more substantially nonorthogonal surface portions comprise said sloping surface portions.

104. The illumination system of claim 77, wherein said central region of said elongate member has a top, a bottom, and first and second sides, and peaks and valleys connected by sloping surface portions on at least one of said top and bottom and on at least one of said first and second sides.

109. The illumination system of claim 77, wherein said elongate member comprises an optical path extending in a longitudinal direction from said input end through said central region to said output end, said peaks extending along a direction parallel to said longitudinal direction.

110. The illumination system of claim 77, wherein said elongate member comprises an optical path extending in a longitudinal direction from said input end through said central region to said output end, said peaks oriented at an oblique angle with respect to said longitudinal direction.

111. The illumination system of claim 110, wherein said angle is between about 5 degrees and about 40 degrees.

84. An illumination system comprising:

a plurality of light emitting diodes; and

a solid light pipe having an input end and an output end and a central region therebetween, said input end having a different size or shape than said output end, and at least one of said light emitting diodes displaced from the center of the input end,

wherein said solid light pipe comprises at least one rippled surface in said central region comprising a plurality of peaks and valleys connected by sloping surface portions, at least one of said peaks and valleys at least partially formed by a faceted surface comprising two or more substantially nonorthogonal surface portions or by a rounded surface, such that light entering said input end propagating longitudinally along said central region is deflected by said sloping surface portions of said rippled surface in an azimuthal direction thereby increasing mixing of said light and uniformity at said output end.

85. The illumination system of claim 84, wherein said input end has a different size than said output end.

86. The illumination system of claim 85, wherein said solid light pipe has a length that is sufficiently long such that etendue is substantially conserved from said input end to said output end.

87. The illumination system of claim 84, wherein said input end has a different shape than said output end.

88. The illumination system of claim 84, wherein said input end has a rectilinear shaped aperture and said output end has a curvilinear shaped aperture.

89. The illumination system of claim 84, wherein said peaks and valleys each comprise a vertex at least partially formed by two or more substantially nonorthogonal surface portions.

90. The illumination system of claim 84, wherein said peaks and valleys each comprise a vertex at least partially formed by a rounded portion.

100. The illumination system of claim 84, wherein said two or more substantially nonorthogonal surface portions comprise said sloping surface portions.

105. The illumination system of claim 84, wherein said central region of said solid light pipe has a top, a bottom, and first and second sides, and peaks and valleys connected by sloping surface portions on at least one of said top and bottom and on at least one of said first and second sides.

112. The illumination system of claim 84, wherein said solid light pipe comprises an optical path extending in a longitudinal direction from said input end through said central region to said output end, said peaks extending along a direction parallel to said longitudinal direction.

113. The illumination system of claim 84, wherein said solid light pipe comprises an optical path extending in a longitudinal direction from said input end through said central region to said output end, said peaks oriented at an oblique angle with respect to said longitudinal direction.

114. The illumination system of claim 113, wherein said angle is between about 5 degrees and about 40 degrees.