Backlight scattering element, multiview display, and method having high-index light guide layer
A backlight scattering element, multiview display, and method of backlight scattering element operation employ a high-index light guide layer in conjunction with a light guide and diffraction grating to provide emitted light. The backlight scattering element includes a light guide that guides light as guided light and a high-index light guide layer optically connected to the light guide and configured to extend a thickness of the light guide. The backlight scattering element also includes a diffraction grating adjacent to the high-index light guide layer to diffractively scatter out a portion of the guided light as emitted light. The multiview display includes a light guide having a first layer and a second layer, a refractive index of the second layer being greater than a refractive index of the first layer. The multiview display may modulate diffractively scattered out directional light beams to provide a multiview image.
1. A backlight scattering element comprising:
a light guide configured to guide light as guided light;
a high-index light guide layer optically connected to a surface of the light guide and configured to extend a thickness of the light guide, a refractive index of a material of the high-index light guide layer being greater than a refractive index of a material of the light guide;
a diffraction grating adjacent to the high-index light guide layer, the diffraction grating being configured to diffractively scatter out a portion of the guided light as emitted light; and
a reflective island aligned with and having an extent corresponding to an extent of the diffraction grating, the reflective island being configured to reflect light diffractively scattered by the diffraction grating in a direction corresponding to a direction of the emitted light, wherein the diffraction grating and the reflective island, in combination, represent a reflection mode diffraction grating.
2. The backlight scattering element of claim 1 , wherein the high-index light guide layer is between the reflective island and the light guide, the diffraction grating being located one or both of (a) at an interface between the high-index light guide layer and the light guide, and (b) between the high-index light guide layer and the reflective island.
3. The backlight scattering element of claim 1 , wherein the diffraction grating comprises a first diffraction grating located at an interface between the high-index light guide layer and the light guide, and a second diffraction grating located at a surface of the high-index light guide layer opposite to the interface.
4. The backlight scattering element of claim 3 , wherein the first diffraction grating has a lateral offset from the second diffraction grating, the lateral offset being greater than a spacing between diffractive features of the first and second diffraction gratings.
5. The backlight scattering element of claim 3 , further comprising a reflective island adjacent to the second diffraction grating at the high-index light guide layer surface.
6. The backlight scattering element of claim 1 , wherein the high-index light guide layer is adjacent to a surface of light guide through which the guided light portion is diffractively scattered as the emitted light.
7. The backlight scattering element of claim 1 , wherein the guided light within the light guide is one or both collimated according to a collimation factor and is configured to propagate at a non-zero propagation angle relative a guiding surface of the light guide.
8. A multiview backlight comprising the backlight scattering element of claim 1 , wherein the diffraction grating is configured as a multibeam element of an array of multibeam elements spaced apart from one another along a length of the light guide, each multibeam element of the multibeam element array being configured to diffractively scatter out the guided light portion as the emitted light comprising a plurality of directional light beams having directions corresponding to view directions of a multiview display.
9. A multiview display comprising the multiview backlight of claim 8 , the multiview display further comprising an array of light valves configured to modulate directional light beams of the directional light beam plurality as a multiview image, a size of the multibeam element being between one half and two times a size of a light valve of the light valve array.
10. A multiview display comprising:
a light guide comprising a first layer and a second layer, a refractive index of the second layer being greater than a refractive index of the first layer;
an array of multibeam elements spaced apart from one another along the light guide, each multibeam element of the multibeam element array comprising a diffraction grating adjacent to the second layer of the light guide and being configured to diffractively scatter out a portion of guided light from within the light guide as a plurality of directional light beams having directions corresponding to view directions of the multi view display; and
an array of light valves configured to modulate directional light beams of the directional light beam plurality to provide a multiview image.
11. The multiview display of claim 10 , wherein the diffraction grating of the multibeam element is located at an interface between the first and second layers.
12. The multiview display of claim 10 , wherein the diffraction grating of the multibeam element is located at a surface of the second layer opposite to an interface between the first and second layers.
13. The multiview display of claim 10 , wherein the diffraction grating of a multibeam element of the multibeam element array is located at an interface between the first and second layers, the multibeam element further comprising another diffraction grating located at a surface of the second layer opposite to the interface between the first and second layers.
14. The multiview display of claim 13 , wherein the diffraction grating and the other diffraction grating of the multibeam element have a lateral offset from one another, the lateral offset being configured to optimize a diffractive scattering efficiency of the multibeam element.
15. The multiview display of claim 14 , wherein the multibeam element further comprises a reflective island aligned with and having a size corresponding to the diffraction grating, the reflective island comprising a reflective material configured to reflectively redirect light scattered by the diffraction gratings in a direction corresponding to a direction of the directional light beam plurality.
16. The multiview display of claim 15 , wherein diffractive features of the diffraction grating of the multibeam element comprise the reflective material of the reflective island.
17. A method of backlight scattering element operation, the method comprising:
guiding light in a light guide as guided light, the light guide comprising a first layer and a second layer; and
diffractively scattering out a portion of the guided light from the light guide as emitted light using a diffraction grating located adjacent to the second layer of the light guide,
wherein the second layer comprises a material having a refractive index that is greater than a refractive index of a material of the first layer of the light guide.
18. The method of backlight scattering element operation of claim 17 , further comprising reflecting light diffractively scattered by the diffraction grating in a direction of the emitted light using a reflective island aligned with and having an extent corresponding to an extent of the diffraction grating, wherein the diffraction grating and reflective island, in combination, represent a reflection mode diffraction grating.
19. The method of backlight scattering element operation of claim 17 , wherein the diffraction grating is configured as a multibeam element of an array of multibeam elements spaced apart from one another along a length of the light guide, each multibeam element of the multibeam element array diffractively scattering out the guided light portion as the emitted light comprising a plurality of directional light beams having directions corresponding to view directions of a multiview display.