Elliptical diffusers used in displays

• US 20060239629A1
• Filed: 04/19/2006
• Published: 10/26/2006
• Est. Priority Date: 04/20/2005
• Status: Active Grant

• Current Assignee: Wavefront Technology, Inc.
• Original Assignee: Wavefront Technology, Inc.
• Inventors: Qi, Jun, Rich, Christopher Chapman, Petersen, Joel Mikael
• Granted Patent: US 7,430,358 B2
• Time in Patent Office: Days
• US Class Current: 385/146
• CPC Class Codes: G02B 6/0046 Tapered light guide, e.g. wedge-shaped light guide
• CPC Class Codes: G02B 6/0051 Diffusing sheet or layer
• CPC Class Codes: G02B 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer
• CPC Class Codes: G02F 1/133606 including a specially adapted diffusing, scattering or light controlling members

Abstract

A backlit light display comprises a light guide panel, a prismatic film, an asymmetric top diffuser and an LCD. A linear light source is disposed along a side face of the light guide panel. Light from the linear light source is transmitted though the light guide panel where it is spread and uniformly output through a front face to the prismatic film. Light incident on the prismatic film is redirected more along a first direction than along a second direction. This light is directed more normal to the LCD. An asymmetric diffuser is applied between the prismatic film and the LCD panel to smear the periodic information from the prismatic film and eliminate the Moiré fringe pattern resulting from interference between the periodic structure of the prismatic film and the periodic arrangement of pixels in the LCD. The asymmetric diffuser is aligned with respect to the prismatic film such that it scatters and spreads light more in a second direction than the first direction.

Claims

1. A display apparatus comprising:

a light guide comprising substantially optically transmissive material that can propagate light therein, said light guide further comprising an output face for output of said light, said light output from said output face having an angular distribution;

a plurality of anamorphic optical elements disposed forward of said front output face such that light from said output face of said light guide is incident on said anamorphic optical elements, said anamorphic optical elements redirecting said angular distribution along a first direction, y, more than in a second direction, x.

a spatial light modulator forward said plurality of anamorphic optical elements to receive said light from said output face of said light guide; and

an asymmetric diffuser disposed between said anamorphic optical elements and said spatial light modulator, said asymmetric diffuser configured to spread light incident thereon more along said second direction, x, than said first direction, y.

2. The display apparatus of claim 1, further comprising a light source disposed with respect to the light guide to direct light from said light source into said optically transmissive material.

3. The display apparatus of claim 2, wherein said light source comprises a linear light source and said light guide is edge-lit by said linear light source.

4. The display apparatus of claim 2, wherein said light source comprises a fluorescent tube.

5. The display apparatus of claim 2, wherein said light source comprises one or more light emitting diodes.

6. The display apparatus of claim 1, wherein said light guide comprises a plate.

7. The display apparatus of claim 1, wherein said light guide comprises a wedge.

8. The display apparatus of claim 1, wherein said optically transmissive material comprises glass or plastic.

9. The display apparatus of claim 1, further comprising extractors that scatter light guided within said light guide such that said light exits said output face of said light guide.

10. The display apparatus of claim 1, further comprising an optical layer, said plurality of anamorphic optical elements being disposed on a rear surface of said optical layer, said rear surface facing said light guide.

11. The display apparatus of claim 10, wherein said optical layer comprises a polymeric sheet.

12. The display apparatus of claim 1, wherein said plurality of anamorphic optical elements comprise a plurality of elongate microprisms each comprising facets angled with respect to each other, said plurality of elongate microprisms disposed on a prismatic layer.

13. The display apparatus of claim 12, wherein said facets are oriented with respect to each other at an angle of between about 50°

and 75°

.

14. The display apparatus of claim 12, wherein said facets are oriented with respect to each other at an angle of between about 85°

and 95°

.

15. The display apparatus of claim 12, wherein said facets are disposed on a rear surface of a prismatic layer, said rear surface facing said light guide.

16. The display apparatus of claim 12, wherein only one prismatic layer is disposed between said light guide and said spatial light modulator.

17. The display apparatus of claim 12, wherein said elongate microprisms are lengthwise parallel to each other and to said second direction, x.

18. The display apparatus of claim 17, wherein only prismatic layers that redirect said angular distribution along a first direction, y, more than in a second direction, x, are disposed between said light guide and said spatial light modulator.

19. The display apparatus of claim 1, wherein said first direction, y, is substantially orthogonal to said second direction, x.

20. The display apparatus of claim 1, wherein only anamorphic optical elements that redirect said angular distribution along a first direction, y, more than in a second direction, x are disposed between said light guide and said spatial light modulator.

21. The display apparatus of claim 1, wherein said plurality of anamorphic optical elements are configured such that said light received by said asymmetric diffuser has an angular distribution having a full width half maximum smaller along the first direction, y, of between about 20°

and 90° and

a full width half maximum along the second direction, x, of between about 40° and

170°

.

22. The display apparatus of claim 1, wherein said spatial light modulator comprises a liquid crystal display.

23. The display apparatus of claim 1, wherein said asymmetric diffuser comprises a holographic elliptical diffuser.

24. The display apparatus of claim 1, wherein said asymmetric diffuser is configured to produce a substantially elliptical beam having a beam cross-section having a major and a minor axis when illuminated with a collimated circular beam, said minor axis being aligned with the first direction, y, and the major axis being aligned with said second direction, x.

25. The display apparatus of claim 24, wherein said asymmetric diffuser is configured such that said substantially elliptical beam produced by a collimated circular beam has an angular distribution having a full width half maximum along the first direction, y, of between about 2°

and 15° and

a full width half maximum along the second direction, x, of between about 4° and

30°

.

26. The display apparatus of claim 1, wherein said asymmetric diffuser is configured such that said light from said spatial light modulator has an angular distribution having a full width half maximum smaller along the first direction, y, of between about 2°

and 15° and

a full width half maximum along the second direction, x, of between about 4° and

30°

.

27. A display apparatus comprising:

means for a guiding light, said light guiding means having an output with an angular distribution;

means for redirecting light from said light guiding means, said means for redirecting light redirecting said angular distribution more along a first direction, y, than in a second direction, x;

means for selectively modulating said redirected light as said light passes through a plurality of regions so as to form a plurality of different spatial patterns; and

means for diffusing said redirected light prior to being selectively modulated, said diffusing means configured to spread light incident thereon more along said second direction, x, than said first direction, y.

28. The display apparatus of claim 27, wherein said light guiding means comprises a light guide plate.

29. The display apparatus of claim 27, wherein said light redirecting means comprises a plurality of anamorphic optical elements.

30. The display apparatus of claim 27, wherein said light modulating means comprises a spatial light modulator and said plurality of regions comprise pixels.

31. The display apparatus of claim 27, wherein said light diffusing means comprises an asymmetric diffuser.

32. A method of displaying an image comprising:

outputting light from a planar surface, said light output from said planar surface having an angular distribution;

redirecting said light output from said planar surface such that said angular distribution is redirected more along a first direction, y, than in a second direction, x;

selectively modulating said light as said light passes through a plurality of pixels so as to form a plurality of different spatial patterns; and

diffusing said light more along said second direction, x, than said first direction, y, prior to modulating said light.

33. A display apparatus comprising:

a light guide comprising substantially optically transmissive material that can propagate light therein, said light guide further comprising an output face for output of said light;

a plurality of anamorphic optical elements disposed forward of said front output face such that light from said output face of said light guide is incident on said anamorphic optical elements;

a spatial light modulator forward said plurality of anamorphic optical elements to receive said light from said output face of said light guide; and

an asymmetric diffuser disposed between said anamorphic optical elements and said spatial light modulator.

34. A display apparatus comprising:

a light guide;

a reverse prismatic layer disposed forward of said light guide;

a spatial light modulator forward said reverse prismatic layer; and

an elliptical diffuser disposed between said reverse prismatic layer and said spatial light modulator.

35. A display apparatus comprising:

a light guide comprising substantially optically transmissive material that can propagate light therein, said light guide further comprising an output face for egress of said light;

a plurality of anamorphic optical elements disposed forward of said front output face such that light from said light guide is incident on said anamorphic optical elements, said anamorphic optical elements redirecting said light along a first direction, y, more than in a second direction, x;

a spatial light modulator forward said plurality of anamorphic optical elements to receive said light redirected more along said first direction, y, than said second direction, x; and

an asymmetric diffuser disposed between plurality of anamorphic optical elements and said spatial light modulator, said asymmetric diffuser configured to spread light incident thereon more along said second direction, x, than said first direction, y.