GRATING COUPLED LIGHT GUIDE
A grating-coupled light guide includes a plate light guide and a grating coupler at an input to the plate light guide. The grating coupler is to receive light from a light source and to diffractively redirect the light into the plate light guide at a non-zero propagation angle as guided light. Characteristics of the grating coupler determine a spread angle of the diffractively redirected guided light.
1 . A grating-coupled light guide comprising:
a plate light guide to guide light at a non-zero propagation angle; and
a grating coupler at an input of the plate light guide, the grating coupler to receive light from a light source and to diffractively redirect the light into the plate light guide at the non-zero propagation angle as guided light,
wherein characteristics of the grating coupler are to determine the non-zero propagation angle, a first spread angle, and a second spread angle of the guided light, the first spread angle being in an angle in a plane perpendicular to a surface of the plate light guide and the second spread angle being an angle in a plane parallel to the plate light guide surface.
2 . The grating-coupled light guide of claim 1 , wherein the grating coupler is a transmissive grating coupler comprising a transmission mode diffraction grating at a surface of the plate light guide adjacent to the light source, the transmission mode diffraction grating to diffractively redirect light transmitted through the diffraction grating.
3 . The grating-coupled light guide of claim 2 , wherein a grating material of the grating coupler comprises silicon nitride.
4 . The grating-coupled light guide of claim 3 , wherein the transmission mode diffraction grating comprises grooves in the plate light guide surface, the grooves being filled with the grating material.
5 . The grating-coupled light guide of claim 3 , wherein the grating material is deposited on the plate light guide surface, the transmission mode diffraction grating comprising a plurality of ridges formed in the deposited grating material.
6 . The grating-coupled light guide of claim 1 , wherein the grating coupler is a reflective grating coupler comprising a reflection mode diffraction grating at a surface of the plate light guide opposite a plate light guide surface adjacent to the light source, the reflection mode diffraction grating to diffractively redirect light into the plate light guide using reflective diffraction.
7 . The grating-coupled light guide of claim 6 , wherein the reflective grating coupler further comprises a layer of reflective metal to facilitate reflection by the reflection mode diffraction grating.
8 . The grating-coupled light guide of claim 1 , further comprising the light source, wherein a cone angle of light provided by the light source is greater than about sixty (60) degrees, a central ray of the light provided by the light source to be incident on the grating coupler at an angle that is substantially orthogonal to a surface of the plate light guide.
9 . The grating-coupled light guide of claim 1 , further comprising the light source, wherein the light to be diffractively redirected into the plate light guide as the guided light is substantially collimated, the light source being an uncollimated light source.
10 . The grating-coupled light guide of claim 1 , wherein the plate light guide is a touch-sensitive panel, a touch of a surface of the plate light guide to be sensed using frustrated total internal reflection of the guided light within the plate light guide.
11 . A multibeam grating-based backlight comprising the grating-coupled light guide of claim 1 , the multibeam grating-based backlight further comprising:
a multibeam diffraction grating adjacent to the plate light guide surface to couple out a portion of the guided light as a plurality of light beams, a principal angular direction of a light beam of the light beam plurality being different from principal angular directions of other light beams of the light beam plurality.
12 . A grating-coupled light guide system comprising:
a light source to provide uncollimated light, the uncollimated light being provided in a first direction;
a plate light guide to guide light at a non-zero propagation angle in a second direction substantially orthogonal to the first direction; and
a grating coupler to receive the uncollimated light in the first direction from the light source and to diffractively redirect the light into the plate light guide at the non-zero propagation angle and in the second direction as guided light,
wherein a characteristic of the grating coupler is to determine the non-zero propagation angle and a spread angle of the guided light.
13 . The grating-coupled light guide system of claim 12 , further comprising:
a plurality of light sensors at an edge of the plate light guide to detect the guided light, the plurality of light sensors to determine a location at which a surface of the plate light guide is touched using frustrated total internal reflection of the guided light,
wherein the grating-coupled light guide system is a touch-sensitive panel system.
14 . The grating-coupled light guide system of claim 12 , further comprising:
an array of multibeam diffraction gratings at a surface of the plate light guide, each multibeam diffraction grating of the array to couple out a portion of the guided light as a plurality of light beams, a principal angular direction of a light beam of the light beam plurality being different from principal angular directions of other light beams of the light beam plurality,
wherein the grating-coupled light guide system is a multibeam grating-based backlight.
15 . The grating-coupled light guide system of claim 14 , wherein the array of multibeam diffraction gratings comprises a linear chirped diffraction grating.
16 . The grating-coupled light guide system of claim 14 , wherein a multibeam diffraction grating of the array comprises one of curved grooves in the plate light guide surface and curved ridges on the plate light guide surface that are spaced apart from one another.
17 . A three-dimensional (3-D) electronic display comprising:
a plate light guide to guide light at a non-zero propagation angle;
a grating coupler to diffractively couple light into the plate light guide as a beam of guided light at the non-zero propagation angle and having a predetermined spread angle;
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 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 plurality of light beams, the modulated plurality of light beams representing pixels of the 3-D electronic display.
18 . The 3-D electronic display of claim 17 , wherein the array of multibeam diffraction gratings comprises a chirped diffraction grating having curved diffractive features, and wherein the light valve array comprises a plurality of liquid crystal light valves.
19 . A method of coupling light into a plate light guide, the method comprising:
generating light using a light source;
coupling the light from the light source into the plate light guide using a grating coupler; and
guiding the coupled light in the plate light guide at a non-zero propagation angle as guided light,
wherein the guided light includes a propagating light beam directed at the non-zero propagation angle by the grating coupler and having a predetermined first spread angle in a plane perpendicular to a surface of the plate light guide and a predetermined second spread angle in a plane substantially parallel to the plate light guide surface, the predetermined first and second spread angles being determined by characteristics of the grating coupler.
20 . The method of coupling light into a light guide of claim 19 , wherein the grating coupler comprises a transmissive grating at a light-source adjacent surface of the plate light guide.
21 . A method of electronic display comprising the method of coupling light into a light guide of claim 19 , further comprising:
diffractively coupling out a portion of the guided light using a multibeam diffraction grating at the surface of the plate light guide to produce a plurality of light beams directed away from the plate light guide in a plurality of different principal angular directions; and
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.