Optics arrangements including light source arrangements for an active matrix liquid crystal image generator

• US 5,808,800 A
• Filed: 12/22/1994
• Issued: 09/15/1998
• Est. Priority Date: 12/22/1994
• Status: Expired due to Term

• Current Assignee: Citizen Finetech Miyota Company Limited (Citizen Electronics Company Limited)
• Original Assignee: DT FLCO, Inc. (Micron Technology, Inc.)
• Inventors: Handschy, Mark A., Meadows, Michael R., Chase, Holden
• Primary Examiner(s): Epps, Georgia Y.
• Assistant Examiner(s): BEY, DAWN MARIE
• Application Number:
  US08/362,234
• Time in Patent Office: 1,363 Days
• Field of Search: 359/263, 359/277, 359/292, 359/629, 359/630, 359/631, 359/632, 359/633, 359/290, 359/291, 349/11
• US Class Current: 359/630
• CPC Class Codes: G02B 27/1033 having a single light modulator for all colour channels
• CPC Class Codes: G02B 27/1053 having a single light modulator for all colour channels
• CPC Class Codes: G02B 27/1086 operating by diffraction only
• CPC Class Codes: G02B 27/123 The splitting element being a lens or a system of lenses, including arrays and surfaces with refractive power
• CPC Class Codes: G02B 27/145 having sequential partially reflecting surfaces
• CPC Class Codes: G02B 27/283 used for beam splitting or combining
• CPC Class Codes: G02B 6/0033 Means for improving the coupling-out of light from the light guide
• CPC Class Codes: G02B 6/0056 for producing polarisation effects, e.g. by a surface with polarizing properties or by an additional polarizing elements
• CPC Class Codes: G02F 1/133526 Lenses, e.g. microlenses or Fresnel lenses
• CPC Class Codes: G02F 1/1336 Illuminating devices
• CPC Class Codes: G02F 1/133606 including a specially adapted diffusing, scattering or light controlling members
• CPC Class Codes: G02F 1/133609 including means for improving the color mixing, e.g. white
• CPC Class Codes: G02F 1/133616 Front illuminating devices
• CPC Class Codes: G02F 1/13362 providing polarized light, e.g. by converting a polarisation component into another one
• CPC Class Codes: G02F 1/133622 Colour sequential illumination
• CPC Class Codes: G02F 1/136277 formed on a semiconductor substrate, e.g. of silicon
• CPC Class Codes: Y10S 362/80 Light emitting diode

Abstract

A system for producing modulated light is disclosed. The system comprises a spatial light modulator including a light modulating medium switchable between different states so as to act on light in ways which form overall patterns of modulated light. The system also includes an arrangement for switching the modulating medium between the different states in a controlled way and an illumination arrangement for producing a source of light. The system further includes an optics arrangement for directing light from the source of light into the spatial light modulator and for directing light from the spatial light modulator through a predetermined source imaging area. The optics arrangement cooperates with the illumination arrangement and the spatial light modulator so as to produce a real image of the source of light within the source imaging area such that an individual is able to view a virtual image of the overall patterns of modulated light from the source imaging area. A variety of novel optics arrangements are disclosed including specific combinations of different light sources, diffusing plates, polarizers, beam splitters, analyzers, lenses, mirrors, and holographic optical elements which allow the overall optical arrangement to be miniaturized to the same degree and in coordination with the spatial light modulator. The different light sources include using a plurality of light sources, such as LEDs, to form an array of light sources, each of the light sources providing light to a corresponding portion of the spatial light modulator.

Claims

1. A display system for producing modulated light which may be viewed by a viewer, the display system comprising:

(a) a spatial light modulator including a light modulating medium switchable between different states so as to act on light in ways which form overall patterns of modulated light;

(b) means for switching said modulating medium between said different states in a controlled way;

(c) illumination means for producing a source of light; and

(d) optics means for directing light from said source of light into said spatial light modulator and for directing light from said spatial light modulator through a predetermined source imaging area, said optics means cooperating with said illumination means and said spatial light modulator so as to produce a real image of said source of light within said source imaging area such that a virtual image of only said overall patterns of modulated light produced by said spatial light modulation is directly visible by said viewer from said source imaging area.

2. A system according to claim 1 wherein substantially all of the light directed from said spatial light modulator is directed through said source imaging area except for any light which is specifically absorbed or directed away from said source imaging area by other optical elements positioned within the optical path between said spatial light modulator and said source imaging area.

3. A system according to claim 1 wherein the spatial light modulator is a reflective type spatial light modulator and wherein said optics means cooperates with said illumination means and said spatial light modulator such that some of the light passing from said illumination means to said spatial light modulator overlaps with some of the light passing from said spatial light modulator to said source imaging area.

4. A system according to claim 1 wherein said source imaging area is at least approximately 3 mm in diameter and at most approximately 20 mm in diameter.

5. A system according to claim 4 wherein any non-illuminated subareas that might be present within said source imaging area has a maximum extent of at most 3 mm, whereby said viewer that is viewing said virtual image of the overall patterns can do so continuously even if the viewer'"'"'s pupil moves anywhere within the source imaging area including any of the non-illuminated subareas.

6. A system according to claim 1 wherein said spatial light modulator is a reflective type spatial light modulator including a light reflecting surface and wherein said optics means includes an eyepiece lens positioned between said spatial light modulator and said source imaging area for establishing said source imaging area.

7. A system according to claim 6 wherein said light reflecting surface is sufficiently specular and cooperates with said illumination means and said optics means such that more than 20 percent of the light reflected from said light reflecting surface would be directed into said eyepiece if no other optical elements were positioned within the optical path between said reflecting surface and said eyepiece lens.

8. A system according to claim 1 wherein said spatial light modulator is a reflective type spatial light modulator, wherein said illumination means includes a plurality of sources of light positioned a first distance from one another, and wherein said optics means, cooperating with said illumination means and said spatial light modulator, produces real images of said plurality of sources of light within said source imaging area such that said real images are spaced apart a second distance from one another which is proportional to said first distance.

9. A system according to claim 8 wherein said second distance is no more than approximately 3 mm.

10. A system according to claim 8 wherein said optics means includes a single collimating lens disposed optically between said plurality of light sources and said spatial light modulator.

11. A system according to claim 8 wherein said optics means includes an equal plurality of collimating lenses, each of which is disposed optically between an associated one of said plurality of light sources and said spatial light modulator so as to direct light to a corresponding part of said spatial light modulator.

12. A system according to claim 11 wherein said optics means includes a single eyepiece lens which is disposed optically between said spatial light modulator and said source imaging area and which has a much greater focal length than the focal length of each of the individual collimating lenses, and wherein each of said light sources is disposed optically approximately a focal length away from its associated collimating lens such that the plurality of images produced at said source imaging area are substantially larger than their respective light sources.

13. A system according to claim 12 wherein each of said collimating lens has a focal length of between approximately 0.25 mm and 10 mm and wherein said eyepiece lens has a focal length of between approximately 12 and 40 mm.

14. A system according to claim 12 wherein each of said light sources is disposed optically slightly closer to its associated collimating lens than one focal length so as to cause each collimating lens to direct light from its associated light source to said spatial light modulator in a slightly diverging manner.

15. A system according to claim 14 wherein the spatial relationship between said light sources and the divergence of said light from said collimating lenses are such that the plurality of images produced at said source imaging area overlap one another in a predetermined way.

16. A system according to claim 8 wherein each of said plurality of light sources is defined by an LED.

17. A system according to claim 16 wherein the distance between any pair of adjacent LEDs is no more than approximately 4 mm, and wherein said optics means is configured so as to produce at said source imaging location an equal plurality of images, adjacent ones of which are spaced from one another no more than approximately 3 mm.

18. A system according to claim 17 wherein said illumination means includes a dielectric substrate having on one surface thereof a pattern of electrically conductive leads adapted for connection to a source of electric power, and wherein said LEDs are individually attached to said substrate and electrically connected with said pattern of leads.

19. A system according to claim 18 wherein said optics means includes an equal plurality of collimating lenses, each of which is connected to said substrate and disposed optically over an associated one of said LEDs between the LEDs and said spatial light modulator so as to direct light to a corresponding part of said spatial light modulator.

20. A system according to claim 16 wherein said illumination means includes a single LED wafer having on one surface thereof a pattern of transverse electrically conductive leads adapted for connection to a source of electric power, said pattern of leads dividing said wafer into said plurality of LEDs.

21. A system according to claim 20 wherein said optics means includes an equal plurality of collimating lenses, each of which is connected to said LED wafer and disposed optically over an associated one of said LEDs between the LEDs and said spatial light modulator so as to direct light to a corresponding part of said spatial light modulator.

22. A system according to claim 21 wherein said optics means includes a single substrate which is attached to said LED wafer and which is integrally formed to define all of said collimating lenses.

23. A system according to claim 16 wherein said illumination means includes a single LED wafer having on one surface thereof a pattern of electrically conductive leads adapted for connection to a source of electric power, wherein said optics means includes an equal plurality of collimating lenses, each of which is connected to said LED wafer and disposed optically over a predetermined segment thereof between the wafer and said spatial light modulator in a way which divides said wafer up into said plurality of LEDs such that the LEDs direct light to corresponding parts of said spatial light modulator.

24. A system according to claim 23 wherein said optics means includes a single substrate which is attached to said LED wafer and which is integrally formed to define all of said collimating lenses.

25. A system according to claim 8 wherein said plurality of spaced apart light sources includes LEDs of more than one color.

26. A system according to claim 25 wherein said multi-colored LEDs includes red, green and blue LEDs spatially arranged in a predetermined pattern relative to one another.

27. A system according to claim 8 wherein said optics means includes a light diffusing plate disposed between said plurality of light sources and said spatial light modulator.

28. A system according to claim 27 wherein said light sources are spaced apart a predetermined distance d and which emit light outwardly at an effective maximum angle A, wherein said light diffusing plate is spaced from said light sources at least a distance L, and wherein the positional relationship between said light sources and said diffusing plate is such that there is sufficient mixing of the light from said light sources so as to achieve a substantially uniform brightness of light throughout said source imaging area.

29. A system according to claim 28 wherein L is greater than or equal to d/A.

30. A system according to claim 28 wherein said optics means includes a single collimating lens disposed optically between all of said light sources and said spatial light modulator.

31. A system according to claim 30 wherein said single collimating lens is a Fresnel lens.

32. A system according to claim 28 wherein said optics means includes a plurality of collimating lenses, each of which is disposed optically between an associated one of said plurality of light sources and said spatial light modulator.

33. A system according to claim 28 wherein said plurality of sources of light include different color light sources and wherein the positional relationship between said light sources and said diffusing plate is such that there is sufficient mixing of the light from said different color light sources so as to be able to achieve a substantially uniform white light throughout said source imaging area.

34. A system according to claim 33 wherein said light sources are red, green, and blue LEDs.

35. A system according to claim 34 wherein said light sources consist of two red, three green and two blue LEDs.

36. A system according to claim 8 wherein said optics means includes a combination polarizer-beam splitter-analyzer optically disposed between both said light sources and spatial light modulator and between said spatial light modulator and source imaging area so as to direct light from said sources to said spatial light modulator and from said spatial light modulator to said source imaging location.

37. A system according to claim 36 wherein said optics means further includes an auxiliary polarizer optically disposed between said light sources and said combination polarizer-beam splitter-analyzer.

38. A system according to claim 36 wherein said optics means further includes an auxiliary analyzer optically disposed between said combination polarizer-beam splitter-analyzer and said source imaging location.

39. A system according to claim 36 wherein said light sources include sources of first, second and third different colors, wherein said combination polarizer-beam splitter-analyzer is tuned to said second color such that it most efficiently polarizes and analyzes light of said second color, and wherein said optics means cooperate with said different color light sources (i) such that substantially collimated light from said second source is directed into said combination polarizer-beam splitter-analyzer normal to a predetermined surface thereof, (ii) such that substantially collimated light from said first source is directed into said combination polarizer-beam splitter-analyzer at a second different predetermined angle with respect to said predetermined surface, and (iii) such that substantially collimated light from said third source is directed into said combination polarizer-beam splitter-analyzer at a third different predetermined angle with respect to said predetermined surface, said different angles being selected to improve the efficiency said combination polarizer-beam splitter-analyzer polarizes and analyzes the light from said first and third sources, given that it is tuned to the light from said second source.

40. A system according to claim 39 wherein said first light source is a red light source, said second light source is a green light source and said third light source is a blue light source.

41. A system according to claim 1 wherein said spatial light modulator is a reflective type spatial light modulator, wherein said illumination means forms at least one source of light having a certain spatial extent, and wherein said optics means, cooperating with said illumination means and said spatial light modulator, produces a real image of said source of light which substantially fills said source imaging area.

42. A system according to claim 41 wherein said optics means includes a combination polarizer-beam splitter-analyzer optically disposed between both said light source and said spatial light modulator and between said spatial light modulator and said source imaging area so as to direct light from said source to said spatial light modulator and from said spatial light modulator to said source imaging location.

43. A system according to claim 42 wherein said optics means further includes a polarizer positioned optically between said light source and said spatial light modulator and an analyzer positioned optically between said spatial light modulator and said source imaging area.

44. A system according to claim 42 wherein said beam splitter is a polarizer-beam splitter-analyzer.

45. A system according to claim 44 wherein said optics means further includes an auxiliary polarizer optically disposed between said light source and said combination polarizer-beam splitter-analyzer.

46. A system according to claim 45 wherein said optics means further includes an auxiliary analyzer optically disposed between said combination polarizer-beam splitter-analyzer and said source imaging location.

47. A system according to claim 41 wherein the light directed to said spatial light modulator from said source is unpolarized light and wherein said optics means includes a combination polarizer-beam splitter-analyzer optically disposed between both said light source and spatial light modulator and between said spatial light modulator and source imaging area so as to direct light from said source to said spatial light modulator and from said spatial light modulator to said source imaging location, said combination polarizer-beam splitter-analyzer acting on one polarization state of said light in a way that directs it to said spatial light modulator and acting on the opposite polarization state of said light in a way that directs it away from said spatial light modulator, said optics means further including (i) means for redirecting the light of said opposite polarization state back toward a point immediately adjacent but to one side of said light source, (ii) means located at said point for redirecting the last-mentioned light back to said spatial light modulator through said combination polarizer-beam splitter-analyzer, and (iii) means for converting the last-mentioned light to said one polarization state before it returns to said combination polarizer-beam splitter-analyzer.

48. A system according to claim 41 wherein the light directed to said spatial light modulator from said source is unpolarized light and wherein said optics means includes (i) a first and a second combination polarizer-beam splitter-analyzer optically disposed between both said light source and said spatial light modulator and between said spatial light modulator and said source imaging area so as to direct light from said source to said spatial light modulator and from said spatial light modulator to said source imaging location, and (ii) means positioned between said first and second combination polarizer-beam splitter-analyzer for converting light of one polarization state to light of the opposite polarization state, said first combination polarizer-beam splitter-analyzer acting on said opposite polarization state of said light in a way that directs it to a corresponding portion of said spatial light modulator and acting on said one polarization state of said light in a way that directs it to said second combination polarizer-beam splitter-analyzer through said means for converting light of said one polarization state to light of said opposite polarization state, said second combination polarizer-beam splitter-analyzer acting on said opposite polarization state of said light in a way that directs it to a second corresponding portion of said spatial light modulator.

49. A system according to claim 41 wherein optics means includes a holographic optical element cooperating with said light source and said spatial light modulator in a way which provides said image of said source at said source imaging area.

50. A system according to claim 49 wherein said holographic optical element is a holographic polarizing beam splitter.

51. A system according to claim 50 wherein said optics means further includes an auxiliary polarizer optically disposed between said light sources and said holographic polarizing beam splitter.

52. A system according to claim 50 wherein said optics means further includes an auxiliary analyzer optically disposed between said holographic polarizing beam splitter and said source imaging location.

53. A system according to claim 52 wherein said light source is at least one LED.

54. A system according to claim 53 wherein said light source is a plurality of LEDs of different colors.

55. A system according to claim 49 wherein said holographic optical element is an edge illuminated holographic illuminator.

56. A system according to claim 55 wherein said light source is at least one laser diode.

57. A system according to claim 56 wherein said light source is a plurality of laser diodes of different colors.

58. A system according to claim 41 wherein said spatial light modulator includes a planar light receiving surface, wherein said optics means directs light from said light source into said spatial light modulator at an acute angle to an axis normal to and centrally located with respect to said light receiving planar surface and from said spatial light modulator in a way which provides said image of said source at said source imaging area, wherein said light source has a corresponding polarizer positioned adjacent to said light source between said light source and said spatial light modulator, and wherein said optics means includes an analyzer positioned between said spatial light modulator and said source imaging area.

59. A system according to claim 58 wherein said optics means is configured such that all of the light leaving said spatial light modulator does so at acute angles to said normal axis and asymmetrically with respect to the spatial light modulator and wherein said optics means includes an eyepiece lens positioned between said spatial light modulator and said source imaging area and positioned laterally to one side of an axis relative to said normal axis.

60. A system according to claim 59 wherein said optics means includes a plurality of light sources of different colors, for example LEDs of different colors.

61. A system according to claim 58 wherein said optics means includes an eyepiece lens positioned between said spatial light modulator and said source imaging location, wherein said light source includes a plurality of light sources positioned at discrete locations around said eyepiece, and wherein said optics means is configured such that all of the light leaving said spatial light modulator does so at acute angles to said normal axis.

62. A system according to claim 61 wherein each of said plurality of light sources includes a plurality of light sources of different colors, for example LEDs of different colors.

63. A system according to claim 41 wherein said optics means directs light from said light source into and from said spatial light modulator in a way which provides an image at a source imaging area and wherein said optics means includes (i) an eyepiece lens positioned between said spatial light modulator and said source imaging location (ii) at least one corresponding polarizer positioned adjacent to said light source between said light source and said spatial light modulator, said light source and corresponding polarizer being positioned between said spatial light modulator and said eyepiece lens, and (iii) an analyzer positioned between said light source and said source imaging location.

64. A system according to claim 63 wherein said light source includes a plurality of light sources of different colors, such as LEDs of different colors.

65. A display system for producing modulated light which may be viewed by a viewer, the display system comprising:

(a) a reflective type spatial light modulator including a light modulating medium switchable between different states so as to act on light in ways which form overall patterns of modulated light;

(b) means for switching said modulating medium between said different states in a controlled way;

(c) illumination means for producing a source of light; and

(d) optics means for directing substantially all of the light from said source of light into said spatial light modulator and for directing substantially all of the light from said spatial light modulator through a predetermined source imaging area except for any light which is specifically absorbed or directed away from said source imaging area by other optical elements positioned within the optical path between said spatial light modulator and said source imaging area, said source imaging area being at least approximately 3 mm in diameter and at most approximately 20 mm in diameter, and said optics means cooperating with said illumination means and said spatial light modulator so as to produce a real image of said source of light within said source imaging area such that (i) a virtual image of only said overall patterns of modulated light produced by said spatial light modulator is directly visible by said viewer from said source imaging area and (ii) any non-illuminated subareas that might be present within said source imaging area has a maximum extent of at most 3 mm, whereby said viewer that is viewing said virtual image of the overall patterns can do so continuously even if the viewer'"'"'s pupil moves anywhere within the source imaging area including any of the non-illuminated subareas.

66. A method for producing modulated light that is viewable by a viewer, the method comprising the steps of:

(a) providing a spatial light modulator including a light modulating medium switchable between different states so as to act on light in ways which form overall patterns of modulated light;

(b) switching said modulating medium between said different states in a controlled way; and

(c) directing light from a source into said spatial light modulator and directing light from said spatial light modulator through a predetermined source imaging area so as to produce a real image of said source of light within said source imaging area such that a virtual image of only said overall patterns of modulated light produced by said spatial light modulator is directly visible by said viewer from said source imaging area.

67. A method according to claim 66 wherein said illumination means produces a plurality of light sources.

68. A method according to claim 67 wherein each of said light source is defined by an LED.

69. A method according to claim 67 including the step of providing an equal plurality of collimating lenses, each of which is disposed optically in front of an associated one of said light sources.

70. A method according to claim 69 including the step of positioning said light sources relative to their respective collimating lenses such that light passing through said lenses from said sources diverges outwardly slightly so as to overlap on another.