Diffraction grating-based backlighting having controlled diffractive coupling efficiency

Patent metadata

Field	Value
Publication number	US-10684404-B2
Application number	US-201715640173-A
Country	US
Kind code	B2
Filing date	Jun 30, 2017
Priority date	Jan 10, 2015
Publication date	Jun 16, 2020
Grant date	Jun 16, 2020

Abstract

Diffraction grating-based backlighting having controlled diffractive coupling efficiency includes a light guide and a plurality of diffraction gratings at a surface of the light guide. The light guide is to guide light and the diffraction gratings are to couple out a portion of the guided light using diffractive coupling and to direct the coupled-out portion away from the light guide surface as a plurality of light beams at a principal angular direction. Diffraction gratings of the plurality include diffractive features having a diffractive feature modulation configured to selectively control a diffractive coupling efficiency of the diffraction gratings as a function of distance along the light guide surface.

First claim

What is claimed is:

1. A diffraction grating-based backlight having controlled diffractive coupling efficiency, the diffraction grating-based backlight comprising:
a light guide configured to guide light as a guided light beam at a non-zero propagation angle relative to a surface of the light guide, the guided light beam being collimated; and
a plurality of diffraction gratings spaced apart from one another along the surface of the light guide, each diffraction grating of the plurality of diffraction gratings being configured to diffractively couple out a portion of the guided light beam as a plurality of coupled-out light beams having predetermined principal angular directions within a light field corresponding to different view directions of a three-dimensional (3-D) electronic display that provides 3-D information,
wherein individual diffraction gratings of the plurality of diffraction gratings each comprise diffractive features having a diffractive feature modulation configured to selectively control a diffractive coupling efficiency of the individual diffraction gratings as a function of a distance of the individual diffraction grating along the light guide surface to compensate for a variation in an intensity of the guided light with the distance.

2. The diffraction grating-based backlight of claim 1 , wherein the plurality of diffraction gratings comprises a multibeam diffraction grating configured to couple out the portion of the guided light beam as the plurality of coupled-out light beams.

3. The diffraction grating-based backlight of claim 2 , wherein the multibeam diffraction grating is a linearly chirped diffraction grating having curved diffractive features.

4. The diffraction grating-based backlight of claim 2 , wherein the plurality of coupled-out light beams having different principal angular directions is configured to form pixels corresponding to different views of the 3-D electronic display.

5. The diffraction grating-based backlight of claim 1 , wherein the diffractive feature modulation comprises modulation of diffractive feature amplitude.

6. The diffraction grating-based backlight of claim 1 , wherein the diffractive feature modulation comprises modulation of a duty cycle of the diffractive features of the diffraction gratings.

7. The diffraction grating-based backlight of claim 1 , wherein the plurality of diffraction gratings comprises diffraction gratings having substantially equal size.

8. The diffraction grating-based backlight of claim 1 , wherein the diffractive feature modulation comprises subwavelength gaps in the diffractive features, the subwavelength gaps being configured to modulate an effective local diffractive coupling strength of the diffractive features.

9. The diffraction grating-based backlight of claim 1 , wherein the diffractive feature modulation is substantially uniform along a length of the light guide surface.

10. The diffraction grating-based backlight of claim 1 , wherein the diffractive feature modulation is configured to compensate for an exponential decrease in an intensity of the guided light beam due to the diffractive coupling out of the guided light beam portion, the compensation to provide substantially uniform intensity of light beams diffractively coupled-out by the plurality of diffraction gratings as a function of distance along the light guide surface.

11. An electronic display comprising the diffraction grating-based backlight of claim 1 , the electronic display being the 3-D electronic display wherein the coupled-out light beam corresponds to a pixel of the 3-D electronic display.

12. The 3-D electronic display of claim 1 , further comprising a light valve configured to modulate the coupled-out light beam, the diffraction grating being at the surface of the light guide that is adjacent to the light valve.

13. A three-dimensional (3-D) electronic display comprising:
a plate light guide to guide light as guided light;
an array of multibeam diffraction gratings having a diffractive feature modulation configured to selectively control a diffractive coupling efficiency of the multibeam diffraction gratings as a function of distance along the array, each multibeam diffraction grating of the multibeam diffraction grating array being configured to couple out a portion of the guided light as a plurality of light beams according to the controlled diffractive coupling efficiency and having a corresponding plurality of different principal angular directions configured to form a light field; and
a light valve array configured to modulate the light beams having the different principal angular directions to represent pixels corresponding to different views of the 3-D electronic display, the different principal angular directions of the light beams forming the light field corresponding to view directions of the different views.

14. The 3-D electronic display of claim 13 , wherein the diffractive feature modulation comprises one or more of modulation of an amplitude of diffractive features of the multibeam diffraction gratings, modulation of a duty cycle of the diffractive features of the multibeam diffraction gratings, and modulation of an effective density of the diffractive features.

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

16. The 3-D electronic display of claim 13 , wherein the light valve array comprises a plurality of liquid crystal light valves.

17. The 3-D electronic display of claim 13 , further comprising a light source, the guided light being light from the light source that is coupled into an edge of the plate light guide and guided at a non-zero propagation angle as a substantially collimated guided light beam within the plate light guide.

18. A method of three-dimensional (3-D) electronic display operation, the method comprising:
guiding light in a light guide as guided light;
providing a controlled diffraction coupling efficiency of diffraction gratings of a plurality of diffraction gratings spaced apart from one another along a surface of the light guide by modulating diffractive features of each of the diffraction gratings as a function of a distance of each of the diffraction gratings along the light guide surface to compensate for a variation of an intensity of the guided light with the distance; and
diffractively coupling out a portion of the guided light using the plurality of diffraction gratings according to the controlled diffraction coupling efficiency, diffractively coupling out producing a plurality of light beams directed away from the light guide surface at predetermined principal angular directions to form a light field,
wherein the light beams of the light beam plurality correspond to pixels of the 3-D electronic display that displays 3-D information, the predetermined principal angular directions of the light beams corresponding to view directions of different views of the 3-D electronic display.

19. The method of 3-D electronic display operation of claim 18 , wherein modulating the diffractive features comprises one or more of modulating an amplitude of diffractive features, modulating a duty cycle of the diffractive features, and modulating an effective density of the diffractive features.

20. The method of 3-D electronic display operation of claim 19 , further comprising modulating the plurality of light beams using a corresponding plurality of light valves, wherein the diff

Assignees

• Leia Inc

Inventors

• Fattal David A

Classifications

• G02B30/33

  involving directional light or back-light sources · CPC title

• G02B5/1828 Primary

  having means for producing variable diffraction (controlling the direction of light by means of one or more diffracting elements G02B26/0808; acousto-optical elements G02F1/11, G02F1/33; electro- or magneto-optical diffraction G02F1/292, G02F1/2955) · CPC title

• G02B6/0036 Primary

  2-D arrangement of prisms, protrusions, indentations or roughened surfaces · CPC title

• G02F2201/305

  diffraction grating · CPC title

• G02F1/292

  by controlled diffraction or phased-array beam steering (controlled diffraction for optical switching G02F1/31) · CPC title