Apparatus and methods for illuminating optical systems

• US 20050018309A1
• Filed: 05/24/2004
• Published: 01/27/2005
• Est. Priority Date: 05/22/2003
• Status: Active Grant

• Current Assignee: Synopsys Incorporated
• Original Assignee: Optical Research Associates (Synopsys Incorporated)
• Inventors: McGuire, James R. Jr., Cassarly, William J.
• Granted Patent: US 7,196,849 B2
• Time in Patent Office: Days
• US Class Current: 359/630
• CPC Class Codes: G02B 27/0081 with means for altering, e.g. enlarging, the entrance or exit pupil

Abstract

Various embodiments involving structures and methods for illumination can be employed, for example, in projectors, head-mounted displays, helmet-mounted displays, back projection TVs, flat panel displays as well as other optical systems. Certain embodiments may include prism elements for illuminating, for example, a spatial light modulator. Light may be coupled to the prism in some cases using fiber optics or lightpipes. The optical system may also include a diffuser having scatter features arranged to scatter light appropriately to produce a desired luminance profile. Other embodiments are possible as well.

Claims

1. A head mounted display for forming images in a user'"'"'s eye, said apparatus comprising:

a spatial light modulator comprising an array of pixels that can be selectively modulated to create a pattern;

a light source outputting light that is split into first and second portions having substantially identical wavelength characteristics;

first and second separate optical paths for said first and second portions of light, respectively;

first and second reflective surfaces in said first and second optical paths, said first and second reflective surfaces facing different directions and being oriented to reflect said first and second portions of light to first and second sections of said spatial light modulator;

imaging optics disposed with respect to said spatial light modulator to receive light from said first and second sections of said spatial light modulator for imaging said pattern formed by said spatial light modulator; and

a head gear for supporting at least said spatial light modulator and imaging optics.

2. The head mounted display of claim 1, wherein said head mounted display light source comprises an array of light emitting diodes.

3. The head mounted display of claim 1, wherein said head mounted display light source comprises red, blue, and green light emitting diodes.

4. The head mounted display of claim 1, further comprising conveyances for guiding light along said first and second optical paths.

5. The head mounted display of claim 4, wherein said conveyances comprise optical fibers.

6. The head mounted display of claim 4, wherein said conveyances comprise light pipes.

7. The head mounted display of claim 1, further comprising an optical fiber bundle that is split to form said first and second optical paths.

8. The head mounted display of claim 1, wherein said first and second reflective surfaces comprise polarization beamsplitting surfaces disposed in a prism element.

9. The head mounted display of claim 8, further comprising polarizers in said first and second optical paths.

10. The head mounted display of claim 1, wherein said first and second sections of said spatial light modulator are adjacent.

11. The head mounted display of claim 1, further comprising optical elements having asymmetry disposed in said first and second optical paths, respectively, said optical elements providing asymmetric beams to illuminate respective asymmetric areas on said spatial light modulator.

12. The head mounted display of claim 11, wherein said optical elements having asymmetry are selected from the group consisting of cylindrical lenses, mixing rods, and fly'"'"'s-eye lenses.

13. The head mounted display of claim 1, further comprising diffusers disposed in said first and second optical paths.

14. The head mounted display of claim 1, wherein said imaging optics includes an optical combiner.

15. A method of forming an image in the eye of a viewer using a head mounted display, said method comprising:

selectively altering a plurality of pixels in said spatial light modulator thereby forming a pattern with said spatial light modulator;

splitting light emitted from a light source into first and second portions, each portion having substantially similar wavelength characteristics;

reflecting said first and second portions of light off of first and second reflective surfaces to respective first and second sections of said spatial light modulator; and

propagating a portion of said light from said first and second sections of said spatial light modulator through said first and second reflective surfaces to imaging optics to form an image of said pattern in said viewer'"'"'s eye.

16. The method of claim 15, wherein said light source comprises a plurality of light emitters and said light from said plurality of light emitters is collected in a mixing area and split into said first and second portions.

17. The method of claim 15, further comprising substantially balancing said said first and second portions of said light from said light source.

18. The method of claim 17, wherein said light from said light source is split such that said first and second portions are substantially equal in intensity.

19. The method of claim 15, wherein said first and second sections of said spatial light modulator are asymmetric and said first and second portions of light are shaped into first and second asymmetric beams.

20. The method of claim 15, wherein substantially all of said light in first portion is directed to said first section of said spatial light modulator and substantially all of said light from said second portion is directed to said second section of said spatial light modulator.

21. The method of claim 15, wherein said first and second portions of light have substantially the same color.

22. A method of manufacturing a head mounted display, said method comprising:

disposing a optical conveyance with respect to a light source to receive light therefrom, said optical conveyance having first and second sections;

disposing distal ends of said first and second sections of said optical conveyance to direct light output from said distal ends to respective first and second reflective surfaces;

orienting said first and second reflective surfaces to aim light output from said first and second sections of said optical conveyance toward respective first and second regions of a spatial light modulator, said first and second sections of said optical conveyance providing substantially balanced optical power to said first and second regions of said spatial light modulator; and

disposing imaging optics with respect to said spatial light modulator to receive light from said first and second regions of said spatial light modulator and to project said light for forming of images of said first and second regions.

23. The method of manufacture of claim 22, wherein said imaging optics has an effective focal point and said spatial light modulator is substantially located at said focal point of said imaging optics to form images of said first and second sections at infinity.

24. Illumination engine for a rear projection TV, said illumination engine comprising:

a spatial light modulator configured to form spatial patterns;

projection optics disposed with respect to said spatial light modulator to project images of said patterns to a rear projection TV screen;

an illumination engine mounting structure, said spatial light modulator and said projection optics affixed to said illumination engine mounting structure;

an optical conveyance disposed to receiving light from an illumination source; and

a prism having first and second inputs and an output disposed with respect to respective first and second regions on said spatial light modulator, said prism providing separate optical paths from said respective first and second input surfaces to said first and second regions of said spatial light modulator,

wherein said optical conveyance is split such that a first portion of said light from said optical conveyance is directed to said first input of said prism element and a second portion of said light from said optical conveyance is directed to said second input of said prism.

25. The illumination engine of claim 24, wherein said prism is disposed between said projection optics and said spatial light modulator.

26. The illumination engine of claim 24, wherein said optical conveyance is split to provide substantially equal intensity illumination of said first and second regions on said spatial light modulator.

27. The illumination engine of claim 24, wherein said optical conveyance is selected from the group consisting of optical fiber and light piping.

28. The illumination engine of claim 24, wherein said spatial light modulator is configured to receive video signals selected from the group consisting of analog video signals and digital video signals.

29. The illumination engine of claim 24, further comprising asymmetric beamshaping optics for providing asymmetric beams for illuminating said first and second regions of said spatial light modulator.

30. A projector for forming an image on a screen comprising:

a spatial light modulator assembly comprising a plurality of pixels that can be selectively altered so as to form an optical pattern;

a light source outputting light that is split into first and second portions;

first and second respective optical paths for said first and second portions of light, respectively, said first and second portions propagating along said first and second optical paths to respective first and second regions of said spatial light modulator; and

projection optics disposed with respect to said spatial light modulator to project an image of said pattern formed by said spatial light modulator onto said screen.

31. The projector of claim 30, wherein said spatial light modulator assembly comprises an array of optical modulators that selectively modulates the polarization of light and a polarization sensitive element for filtering based on polarization.

32. The projector of claim 30, wherein said spatial light modulator assembly comprises a liquid crystal spatial light modulator.

33. A optical system for forming color images comprising:

a spatial light modulator having an electrical input for receiving control signals, said spatial light modulator having first and second regions;

imaging optics disposed with respect to said spatial light modulator to project images of patterns formed by said spatial light modulator;

first, second, and third light sources outputting light having first, second, and third colors respectively;

first, second, and third pairs of light pipes associated with said first, second, and third light sources respectively, said first pair receiving said first color light from said first light source, said second pair receiving second color light from said second light source, and said third pair receiving third color light from said third light source; and

wherein each of said pairs of light pipes has a first and a second distal end that outputs said first, second, and third colors, respectively, said first distal end in each pair being optically coupled to said a first portion of said spatial light modulator and said second portion being coupled to said second region of said spatial light modulator.

34. The color projection system of claim 33, wherein said first, second, and third light sources comprise a red light source, a blue light source, and a green light source respectively.

35. The color projection system of claim 33, wherein said first, second, and third light sources comprise LEDs.

36. The color projection system of claim 33, wherein said light pipes comprise optical fibers.

37. A method of forming an image on a screen, said method comprising:

selectively alter a plurality of pixels in said spatial light modulator;

splitting light emitted from a light source into first and second portions, each portion having substantially similar wavelength characteristics and polarization properties;

propagating said first and second portions along respective first and second optical paths, said first and second optical paths aimed along counter-opposing directions toward a common region;

reflecting said first and second portions of light off of first and second reflective surfaces facing different directions, said first and second portions of light being reflected to respective first and second sections of said spatial light modulator; and

propagating a portion of said light from said first and second sections to imaging optics to form an image of said pattern on said screen.

38. The method of claim 37, wherein said pattern formed by said pixels in said spatial light modulator comprises one or more characters.