MULTIBEAM DIFFRACTION GRATING-BASED COLOR BACKLIGHTING

• US 20160033705A1
• Filed: 07/30/2015
• Published: 02/04/2016
• Est. Priority Date: 07/30/2014
• Status: Active Grant

• Current Assignee: LEIA SPV LLC, Lelis, Inc.
• Original Assignee: Leia Inc.
• Inventors: Fattal, David A.
• Granted Patent: US 9,557,466 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G02B 27/425 in illumination systems mask illumination systems in photolithographic systems G03F7/70158
• CPC Class Codes: G02B 27/4294 in multispectral systems, e.g. UV and visible
• CPC Class Codes: G02B 5/1866 Transmission gratings characterised by their structure, e.g. step profile, contours of substrate or grooves, pitch variations, materials G02B5/1809, G02B5/1828, G02B5/1833, G02B5/1838 and G02B5/1847 take precedence
• CPC Class Codes: G02B 6/0018 Redirecting means on the surface of the light guide
• CPC Class Codes: G02B 6/002 by shaping at least a portion of the light guide, e.g. with collimating, focussing or diverging surfaces
• CPC Class Codes: G02B 6/0031 Reflecting element, sheet or layer
• CPC Class Codes: G02B 6/0035 provided on the surface of the light guide or in the bulk of it
• CPC Class Codes: G02B 6/0036 2-D arrangement of prisms, protrusions, indentations or roughened surfaces
• CPC Class Codes: G02B 6/0068 Arrangements of plural sources, e.g. multi-colour light sources
• CPC Class Codes: H04N 13/324 Colour aspects

Abstract

Multibeam diffraction grating-based color backlighting includes a plate light guide, a multibeam diffraction grating at a surface of the plate light guide, and light sources laterally displaced from one another in a direction corresponding to a propagation axis of the plate light guide. The light sources produce light of different colors. The plate light guide is to guide light from the light sources. The multibeam diffraction grating is to couple out a portion of the guided light using diffractive coupling as a plurality of light beams of different colors in a plurality of different principal angular directions.

Claims

1. A multibeam diffraction grating-based color backlight comprising:

a plurality of light sources of different colors;

a plate light guide to guide light of the different colors produced by the light sources, the light sources being laterally displaced from one another in a direction corresponding to a propagation axis of the plate light guide; and

a multibeam diffraction grating at a surface of the plate light guide to diffractively couple out a portion of the guided light from the plate light guide as a plurality of light beams having the different colors, a light beam of the light beam plurality having a principal angular direction different from principal angular directions of other light beams of the light beam plurality.

2. The multibeam diffraction grating-based color backlight of claim 1, wherein a principal angular direction of a light beam of a color corresponding to a respective light source is a function of the lateral displacement of the respective light source.

3. The multibeam diffraction grating-based color backlight of claim 1, wherein the multibeam diffraction grating comprises a chirped diffraction grating.

4. The multibeam diffraction grating-based color backlight of claim 1, wherein the multibeam diffraction grating comprises one of curved grooves and curved ridges that are spaced apart from one another.

5. The multibeam diffraction grating-based color backlight of claim 1, further comprising a tilted collimator between the plurality of light sources and the plate light guide, the tilted collimator to collimate and tilt light from the light sources and to direct the tilted and collimated light into the plate light guide as the guided light.

6. The multibeam diffraction grating-based color backlight of claim 5, wherein the tilted collimator comprises a collimating reflector to direct the collimated light at a tilt angle relative to a top surface and a bottom surface of the plate light guide, the tilt angle being both greater than zero and less than a critical angle of total internal reflection within the plate light guide, and wherein light from a respective light source of the light source plurality has a corresponding tilt angle determined by both a tilt of the collimating reflector and a lateral displacement of the respective light source relative to a focus of the collimating reflector.

7. The multibeam diffraction grating-based color backlight of claim 6, wherein the collimating reflector is integral to and formed from a material of the plate light guide, the collimating reflector comprising a portion of a doubly curved paraboloid reflector having a first parabolic shape to collimate light in a first direction parallel to a surface of the plate light guide and a second parabolic shape to collimate light in a second direction orthogonal to the first direction.

8. The multibeam diffraction grating-based color backlight of claim 6, wherein the collimating reflector is a shaped reflector, the shaped reflector in conjunction with the laterally displaced light sources to produce a first light beam corresponding to a first color of the different colors of light and to produce a second light beam corresponding to a second color of the different colors, a principal angular direction of the first light beam being about equal to a principal angular direction of the second light beam.

9. A three-dimensional (3-D) color electronic display comprising the multibeam diffraction grating-based color backlight of claim 1, the 3-D electronic display further comprising a light valve to modulate a light beam of the light beam plurality, the light valve being adjacent to the multibeam diffraction grating, wherein the light beam to be modulated by the light valve corresponds to a pixel of an electronic display.

10. A three-dimensional (3-D) color electronic display comprising:

a light source comprising a plurality of optical emitters of different colors laterally displaced from one another;

a tilted collimator to collimate light produced by the light source and to direct the collimated light into a plate light guide at a non-zero tilt angle as guided light;

an array of multibeam diffraction gratings at a surface of the plate light guide to couple out a portion of the guided light as a plurality of light beams representing the different colors and to direct the light beams in a plurality of different principal angular directions away from the plate light guide; and

a light valve array to modulate the differently directed light beams, the modulated differently directed light beams representing pixels of the 3-D color electronic display.

11. The 3-D color electronic display of claim 10, wherein the plurality of optical emitters comprises a first optical emitter to emit red light, a second optical emitter to emit green light, and a third optical emitter to emit blue light, and wherein a principal angular direction of a red light beam from the first optical emitter is substantially similar to a principal angular direction of one or both of a green light beam and a blue light beam respectively from the second and third optical emitters as determined by the lateral displacements of the first optical emitter, the second optical emitter and the third optical emitter relative to one another.

12. The 3-D color electronic display of claim 10, wherein the tilted collimator comprises a collimating reflector having a shaped parabolic reflector surface, the optical emitters being laterally displaced from one another in a direction corresponding to a propagation axis of the plate light guide in a vicinity of a focus of the collimating reflector.

13. The 3-D color electronic display of claim 10, wherein the multibeam diffraction grating comprises a chirped diffraction grating having curved diffractive features.

14. The 3-D color electronic display of claim 10, wherein the plurality of light beams produced by the multibeam diffraction grating is to substantially converge at a point above the plate light guide surface, and wherein the light valve array is located at a distance from the plate light guide surface that is beyond the convergence point of the light beams.

15. The 3-D color electronic display of claim 10, wherein the light valve array comprises a plurality of liquid crystal light valves.

16. The 3-D color electronic display of claim 10, further comprising an emitter time multiplexer to time multiplex the optical emitters of the light source, wherein the time multiplexer is to sequentially activate each of the optical emitters of the light source to produce light of a different color corresponding to the respective activated optical emitter during a corresponding time interval of a plurality of different time intervals.

17. A method of color electronic display operation, the method comprising:

producing light using a plurality of light sources laterally displaced from one another, a light source of the light source plurality producing light of a color different from colors produced by other light sources of the light source plurality;

guiding the produced light in a plate light guide; and

diffractively coupling out a portion of the guided light using a multibeam diffraction grating at a surface of the plate light guide to produce a plurality of light beams having different colors directed away from the plate light guide in a plurality of different principal angular directions,

wherein the light sources are laterally displaced in a direction corresponding to a propagation axis of the plate light guide.

18. The method of color electronic display operation of claim 17, further comprising collimating the produced light and directing the collimated light into the plate light guide using a tilted collimator, wherein the tilted collimator comprises a collimating reflector to direct the collimated light at a tilt angle relative to the plate light guide surface, and wherein the light from a respective light source of the light source plurality has a corresponding tilt angle determined by both a tilt of the collimating reflector and a lateral displacement of the respective light source relative to a focus of the collimating reflector.

19. The method of color electronic display operation of claim 17, further comprising modulating the plurality of light beams using a corresponding plurality of light valves, the modulated light beams forming pixels of a three-dimensional (3-D) electronic display.

20. The method of color electronic display operation of claim 17, further comprising time multiplexing the light sources of the light source plurality, wherein time multiplexing comprises sequentially activating the light sources, an activated light source to produce light of a respective color during a time interval of a plurality of time intervals.