Projection apparatus using telecentric optics

• US 6,758,565 B1
• Filed: 03/20/2003
• Issued: 07/06/2004
• Est. Priority Date: 03/20/2003
• Status: Expired due to Fees

• Current Assignee: Eastman Kodak Company
• Original Assignee: Eastman Kodak Company
• Inventors: Silverstein, Barry D., Cobb, Joshua M.
• Primary Examiner(s): MAHONEY, CHRISTOPHER E
• Application Number:
  US10/392,685
• Time in Patent Office: 474 Days
• Field of Search: 353/30, 353/31, 353/34, 353/102, 349/5, 349/8
• US Class Current: 353/34
• CPC Class Codes: G02B 13/22 Telecentric objectives or lens systems
• CPC Class Codes: G02B 27/283 used for beam splitting or combining
• CPC Class Codes: H04N 5/7416 involving the use of a spatial light modulator, e.g. a light valve, controlled by a video signal
• CPC Class Codes: H04N 9/3105 for displaying all colours simultaneously, e.g. by using two or more electronic spatial light modulators simultaneous projection in colour photography G03B33/10; beam splitting or combining systems per se G02B27/10
• CPC Class Codes: H04N 9/315 Modulator illumination systems general applications of lighting devices F21V; general optical systems G02B; lamp houses for projectors not peculiar to the presence of an electronic spatial light modulator G03B21/20

Abstract

A digital projection apparatus (10) for projection of a multicolor image uniformizes polychromatic light from a light source (20) and provides magnification to the uniformized illumination beam using a base condenser relay (80), providing a reduced numerical aperture for conditioning at a dichroic separator (27). For each monochromatic component color provided from the dichroic separator (27), a reducing relay (82) then demagnifies the illumination beam to provide source illumination to a spatial light modulator (30) at an increased numerical aperture. The modulated beam from the spatial light modulator (30) is then magnified by a magnifying relay lens assembly (28) and directed, at a lower numerical aperture, to a dichroic combiner (26) and to a projection lens (32). As a result, the projection lens (32) has reduced working distance, color shading across the field is minimized, and brightness is optimized.

Claims

1. A projection apparatus for projecting a multicolor image toward a display surface, the apparatus comprising:

(a) a polychromatic light source;

(b) uniformizing means for homogenizing light from said polychromatic light source to provide a uniform illumination field;

(c) a base condenser relay lens for magnifying said uniform illumination field to form a magnified uniform illumination field and for directing said magnified uniform illumination field toward a dichroic separator, said dichroic separator providing colored light for a first, second, and third colored light modulation channel;

(d) wherein each colored light modulation channel is similarly constructed and comprises;

(i) a reducing relay lens for imaging said magnified uniform illumination field and directing said colored light in said colored light modulation channel;

(ii) a spatial light modulator for forming a first image thereon; and

(iii) a magnifying relay lens for focusing and relaying a magnified real image of said first image towards a dichroic combiner;

(e) said dichroic combiner forming a multicolor image by combining said magnified real image from said first colored light modulation channel, said magnified real image from said second colored light modulation channel, and said magnified real image from said third colored light modulation channel; and

(f) a projection lens for projecting said multicolor image toward said display surface.

2. A projection apparatus according to claim 1 wherein said colored light in said first colored light channel is red, said colored light in said second colored light channel is green, and said colored light in said third colored light channel is blue.

3. A projection apparatus according to claim 1 wherein at least one said spatial light modulator is a reflective liquid crystal display (LCD).

4. A projection apparatus according to claim 1 wherein at least one said spatial light modulator is a transmissive liquid crystal display (LCD).

5. A projection apparatus according to claim 1 wherein at least one said spatial light modulator is a digital micromirror device.

6. A projection apparatus according to claim 1 wherein said polychromatic light source comprises a lamp.

7. A projection apparatus according to claim 1 further comprising a polarizer for conditioning the light from said polychromatic light source.

8. A projection apparatus according to claim 1 further comprising a polarizer for conditioning the colored light in said first colored light modulation channel.

9. A projection apparatus according to claim 1 further comprising a color-selective filter for colored light in said first colored light modulation channel.

10. A projection apparatus according to claim 1 wherein said base condenser relay lens is double-telecentric.

11. A projection apparatus according to claim 1 wherein said reducing relay lens in at least one colored light modulation channel is double-telecentric.

12. A projection apparatus according to claim 1 wherein said magnifying relay lens in at least one colored light modulation channel is double-telecentric.

13. A projection apparatus according to claim 1 wherein said first colored light modulation channel further comprises a polarizing beamsplitter for directing said colored light in said first colored light modulation channel to said spatial light modulator.

14. A projection apparatus according to claim 13 wherein said polarizing beamsplitter is a wire-grid polarizing beamsplitter.

15. A projection apparatus of claim 13 wherein said first colored light modulation channel further comprises a prepolarizer located in proximity to said polarizing beamsplitter.

16. A projection apparatus according to claim 1 wherein said dichroic combiner is an X-cube.

17. A projection apparatus according to claim 1 wherein said dichroic combiner is a Philips prism.

18. A projection apparatus according to claim 1 wherein said colored light modulation channel further comprises a prepolarizer.

19. A projection apparatus according to claim 18 wherein said prepolarizer is a wire grid prepolarizer.

20. A projection apparatus according to claim 18 wherein said prepolarizer is located within the optics of said reducing relay lens.

21. A projection apparatus according to claim 1 wherein said colored light modulation channel further comprises an analyzer.

22. A projection apparatus according to claim 21 wherein said analyzer is a wire grid analyzer.

23. A projection apparatus according to claim 1 wherein said dichroic combiner comprises a prism fabricated of amorphous fused silica.

24. A projection apparatus according to claim 1 wherein said dichroic separator comprises a prism fabricated of amorphous fused silica.

25. A projection apparatus according to claim 1 wherein said first colored light modulation channel further comprises a color-selective polarization filter.

26. A projection apparatus according to claim 25 wherein said color-selective polarization filter serves as a waveplate, rotating the polarization state of light within said first colored light modulation channel.

27. A projection apparatus according to claim 1 further comprising a color-selective polarization filter disposed between said dichroic combiner and said projection lens for rotating the polarization state of light from said first colored light modulation channel.

28. A projection apparatus according to claim 1 wherein said dichroic separator provides red and blue light having S-polarization and green light having P-polarization.

29. A projection apparatus according to claim 28 wherein said dichroic combiner combines red and blue light having S-polarization and green light having P-polarization.

30. A projection apparatus according to claim 1 wherein said dichroic separator is a V-prism.

31. A projection apparatus according to claim 1 wherein said dichroic combiner is a V-prism.

32. A projection apparatus of claim 1 further comprising a letterboxing aperture for enhancing the image provided when said spatial light modulator is displaying a first image which underfills said spatial light modulator.

33. A projection apparatus of claim 32 wherein said letterboxing aperture is located in proximity to said multicolor mage.

34. A projection apparatus for projecting a color image onto a display surface, the apparatus comprising:

(a) a polychromatic light source;

(b) uniformizing means for homogenizing light from said polychromatic light source to provide a uniform illumination field;

(c) a base condenser relay lens for magnifying said uniform illumination field to form a magnified uniform illumination field;

(d) color splitting means for splitting said magnified uniform illumination field into a first color modulation channel for forming a magnified first color image and into at least a second color modulation channel for forming a magnified second color image;

(e) a first reducing relay lens for forming a reduced first color illumination field from said magnified illumination field and for directing said reduced first color illumination field towards a first spatial light modulator for forming a first color image;

(f) a first magnifying relay lens for focusing and relaying said first color image to form said magnified first color image;

(g) color combining means for forming a multicolor image by combining said magnified first color image and at least said magnified second color image; and

(h) a projection lens for projecting said multicolor image toward said display surface.

35. A projection apparatus according to claim 34 wherein at least one said spatial light modulator is taken from the group consisting of reflective LCD, transmissive LCD, and digital micromirror device.

36. A projection apparatus according to claim 34 wherein said polychromatic light source comprises a lamp.

37. A projection apparatus according to claim 34 further comprising a polarizer for conditioning the light from said polychromatic light source.

38. A projection apparatus according to claim 34 further comprising a polarizer for conditioning the colored light in said first colored light modulation channel.

39. A projection apparatus according to claim 34 further comprising a color-selective filter for colored light in said first colored light modulation channel.

40. A projection apparatus according to claim 34 wherein said base condenser relay lens is double-telecentric.

41. A projection apparatus according to claim 34 wherein said first reducing relay lens is double-telecentric.

42. A projection apparatus according to claim 34 wherein said first magnifying relay lens in at least one colored light modulation channel is double-telecentric.

43. A projection apparatus according to claim 34 wherein said first color modulation channel further comprises a polarizing beamsplitter for directing colored light in said first color modulation channel to said spatial light modulator.

44. A projection apparatus according to claim 43 wherein said polarizing beamsplitter is a wire-grid polarizing beamsplitter.

45. A projection apparatus according to claim 34 wherein said color modulation channel further comprises a prepolarizer.

46. A projection apparatus according to claim 45 wherein said prepolarizer is a wire grid prepolarizer.

47. A projection apparatus according to claim 45 wherein said prepolarizer is located within the optics of said first reducing relay lens.

48. A projection apparatus according to claim 34 wherein said color modulation channel further comprises an analyzer.

49. A projection apparatus according to claim 48 wherein said analyzer is a wire grid analyzer.

50. A projection apparatus for projecting a color image according to claim 34 further comprising:

(a) a second reducing relay lens for forming a reduced second color illumination field from said magnified illumination field and for directing said reduced second color illumination field towards a second spatial light modulator for forming a second color image; and

(b) a second magnifying relay lens for focusing and relaying said second color image to form said magnified second color image.

51. A projection apparatus of claim 43 wherein said first colored light modulation channel further comprises a prepolarizer located in proximity to said polarizing beamsplitter.

52. A projection apparatus of claim 34 further comprising a letterboxing aperture for enhancing the image provided when said spatial light modulator is displaying a first image which underfills said spatial light modulator.

53. A projection apparatus of claim 52 wherein said letterboxing aperture is located in proximity to said multicolor mage.

54. A method for projecting a multicolor image toward a display surface, the method comprising:

(a) providing a uniform illumination field of polychromatic light;

(b) magnifying said internal image towards a dichroic color separator to obtain a first enlarged color internal image, a second enlarged color internal image, and a third enlarged color internal image;

(c) demagnifying said first enlarged color internal image to form a first reduced color internal image for modulation at a first spatial light modulator to provide a first color modulated image, then magnifying said first color modulated image to form a magnified first color modulated image;

(d) demagnifying said second enlarged color internal image to form a second reduced color internal image for modulation at a second spatial light modulator to provide a second color modulated image, then magnifying said second color modulated image to form a magnified second color modulated image;

(e) demagnifying said third enlarged color internal image to form a third reduced color internal image for modulation at a third spatial light modulator to provide a third color modulated image, then magnifying said third color modulated image to form a magnified third color modulated image; and

(f) combining said magnified first, second, and third color modulated images onto a single axis to form the multicolor image and projecting the multicolor image toward said display surface.

55. A method for projecting a multicolor image according to claim 54 wherein the step of magnifying said internal image comprises the step of directing said internal image through a telecentric base condenser lens.

56. A method for projecting a multicolor image according to claim 54 wherein the step of magnifying said internal image comprises the step of directing said internal image through a double telecentric base condenser lens.

57. A method for projecting a multicolor image according to claim 54 wherein the step of demagnifying said first enlarged color internal image comprises the step of directing said first enlarged color internal image through a telecentric relay lens.

58. A method for projecting a multicolor image according to claim 54 wherein the step of demagnifying said first enlarged color internal image comprises the step of directing said first enlarged color internal image through a double telecentric relay lens.

59. A method for projecting a multicolor image according to claim 54 wherein the step of magnifying said first color modulated image comprises the step of directing said first color modulated image through a telecentric relay lens.

60. A method for projecting a multicolor image according to claim 54 wherein the step of magnifying said first color modulated image comprises the step of directing said first color modulated image through a double telecentric relay lens.

61. A method for projecting a multicolor image according to claim 54 wherein said first spatial light modulator is a reflective LCD.

62. A method for projecting a multicolor image according to claim 54 wherein said first spatial light modulator is a transmissive LCD.

63. A method for projecting a multicolor image according to claim 54 wherein said first spatial light modulator is a digital micromirror device.

64. A method for projecting a multicolor image according to claim 54 further comprising the step of providing a filter in the path of said multicolor image.

65. A method for projecting a multicolor image according to claim 54 wherein the step of combining said magnified first, second, and third color modulated images comprises the step of directing modulated light through a V-prism.

66. A method for projecting a multicolor image toward a display surface, the method comprising:

(a) magnifying a uniform illumination beam and directing said uniform illumination beam toward a color separator to provide a first color illumination beam and at least a second color illumination beam;

(b) demagnifying said first color illumination beam and directing said first color illumination beam toward a first spatial light modulator for modulating said first color illumination beam to form a first color image;

(c) magnifying said first color image to form a magnified first color image; and

(d) forming a multicolor image by combining said magnified first color image with at least one other image having a second color and projecting said multicolor image toward said display surface.

67. A method for projecting a multicolor image according to claim 66 wherein the step of magnifying said illumination beam comprises the step of directing said illumination beam through a telecentric base condenser lens.

68. A method for projecting a multicolor image according to claim 66 wherein the step of magnifying said illumination beam comprises the step of directing said illumination beam through a double telecentric base condenser lens.

69. A method for projecting a multicolor image according to claim 66 wherein the step of demagnifying said first color illumination beam comprises the step of directing said first color illumination beam through a telecentric relay lens.

70. A method for projecting a multicolor image according to claim 66 wherein the step of demagnifying said first color illumination beam comprises the step of directing said first color illumination beam through a double telecentric relay lens.

71. A method for projecting a multicolor image according to claim 66 wherein the step of magnifying said first color image comprises the step of directing said first color image through a telecentric relay lens.

72. A method for projecting a multicolor image according to claim 66 wherein the step of magnifying said first color image comprises the step of directing said first color image through a double-telecentric relay lens.

73. A method for projecting a multicolor image toward a display surface, the method comprising:

(a) providing a uniformized polychromatic illumination beam at a first effective numerical aperture;

(b) magnifying said uniformized illumination beam toward a color separator to provide a color illumination beam having second effective numerical aperture, lower than said first effective numerical aperture;

(c) demagnifying said color illumination beam toward a spatial light modulator to provide an unmodulated illumination beam having a third effective numerical aperture, higher than said second effective numerical aperture;

(d) modulating said unmodulated illumination beam to form a modulated beam;

(e) magnifying said modulated beam to provide a magnified modulated beam having a fourth effective numerical aperture, lower than said third effective numerical aperture; and

(f) directing said magnified modulated beam to a projection lens, and projecting said magnified modulated beam toward said display surface.

74. A method for projecting a multicolor image according to claim 73 wherein the step of providing a uniformized polychromatic illumination beam comprises the step of energizing a lamp.

75. A method for projecting a multicolor image according to claim 73 wherein the step of demagnifying said color illumination beam toward a spatial light modulator comprises the step of directing said color illumination beam toward an LCD spatial light modulator.

76. A method for projecting a multicolor image according to claim 73 wherein the step of demagnifying said color illumination beam toward a spatial light modulator comprises the step of directing said color illumination beam toward a digital micromirror device.

77. A method for projecting a multicolor image according to claim 73 wherein the step of directing said magnified modulated beam to a projection lens comprises the step of directing said magnified modulated beam to a dichroic combiner.

78. A projection apparatus for projecting a multi-color image towards a display surface, wherein said multi-color image is minimally affected by color shading, the apparatus comprising:

(a) a polychromatic light source providing illumination light;

(b) uniformizing means for homogenizing said illumination light from said polychromatic light source to provide a uniform illumination field;

(c) first illumination optics for directing said illumination light and imaging said uniform illumination field to form an intermediate image which is a first magnified uniform illumination field;

(d) a dichroic separator for providing colored light for a first, second, and third colored light modulation channel by splitting said illumination light into three colored light beams;

wherein each of said colored light modulation channels is provided with second illumination optics and a color filter;

wherein said second illumination optics direct the respective colored light beam and provide a second magnified uniform illumination field which is incident onto a spatial light modulator,

(e) a magnifying relay lens in each of said color channels for focusing and relaying the respective colored light beam to provide a magnified real image of said spatial light modulator within a given color channel towards a dichroic combiner;

(f) said dichroic combiner forming a multicolor image by combining said magnified real image from said first colored light modulation channel, said magnified real image from said second colored light modulation channel, and said magnified real image from said third colored light modulation channel;

(g) a projection lens for projecting said multicolor image toward said display surface;

wherein said first illumination optics present said illumination light to said dichroic separator in a nominally telecentric manner, and said first magnified uniform illumination field is larger than said second magnified uniform illumination field;

wherein each of said color filters are oriented nominally at normal incidence to the respective colored light beam; and

wherein said magnifying relay lens in each of said color channels forms said the respective magnified color image with nominally telecentric light.

79. An electronic projection apparatus according to claim 78 wherein one or both of said dichroic separator and dichroic combiner are fabricated from a low absorption optical material, and in particular, from amorphous fused silica.

80. An electronic projection apparatus according to claim 78 wherein either or both of said dichroic separator and said dichroic combiner transfer light wherein one of said colored light beams has light of a first polarization state, and the second and third said color light beams have light of a second polarization state.

81. An electronic projection apparatus according to claim 78 wherein said one of said colored light beams corresponds to green light of the P-polarization state, and said second and third of said colored light beams respectively correspond to red and blue light of the S-polarization state.

82. An electronic projection apparatus according to claim 78 wherein said spatial light modulators are liquid crystal displays.

83. A projection apparatus utilizing spatial light modulators for projecting a multi-color image towards a display surface, wherein said multi-color image is minimally affected by color shading, the apparatus comprising:

(a) a polychromatic light source providing illumination light;

(b) uniformizing means for homogenizing said illumination light from said polychromatic light source to provide a uniform illumination field;

(c) first illumination optics for directing said illumination light to a dichroic separator, which provides colored light for a first, second, and third colored light modulation channel by splitting said illumination light into three colored light beams;

(d) second illumination optics for directing each of said colored light beams to each of said spatial light modulators corresponding to that color, where a uniform illumination field of the respective color is provided;

(e) a magnifying relay lens in each of said color channels for focusing and relaying the respective colored light beam to provide a magnified real image of said spatial light modulator within a given color channel towards a dichroic combiner;

(f) said dichroic combiner forming a multicolor image by combining said magnified real image from said first colored light modulation channel, said magnified real image from said second colored light modulation channel, and said magnified real image from said third colored light modulation channel

(g) a projection lens for projecting said multicolor image toward said display surface;

wherein said illumination light provided to said dichroic separator by said first illumination optics is larger in extent, or smaller in f-number, than each of said colored light beams provided by said second illumination optics at said spatial light modulators;

wherein each of said color filters are oriented nominally at normal incidence to the respective colored light beam;

wherein said magnifying relay lens in each of said color channels forms said the respective magnified color image with nominally telecentric light; and

wherein either or both of said dichroic separator and said dichroic combiner transfer light with said colored light beams corresponding to green light being in the P-polarization state, and said second and third of said colored light beams respectively corresponding to red and blue light being in the S-polarization state.

84. An electronic projection apparatus according to claim 83 wherein one or both of said dichroic separator and dichroic combiner are fabricated from a low absorption optical material, and in particular, from amorphous fused silica.

85. An electronic projection apparatus according to claim 83 wherein said spatial light modulators are liquid crystal displays.