Waveguide comprising surface relief feature and directional backlight, directional display device, and directional display apparatus comprising said waveguide
View Patent ↗An imaging directional backlight apparatus includes a waveguide and light source array for providing large area directed illumination from localized light sources. The waveguide may include a stepped structure in which steps may include extraction features optically hidden to guided light, propagating in a forward direction. Returning light propagating in a backward direction may be refracted, diffracted, or reflected by the features to provide discrete illumination beams exiting from the top surface of the waveguide. Viewing windows are formed through imaging individual light sources and defines the relative positions of system elements and ray paths. Alignment of the waveguide to mechanical and optical components may be provided by surface relief features of the waveguide arranged in regions adjacent the input surface and intermediate the light emitting regions of the light sources. Efficient, uniform operation may be achieved with low cross talk for application to autostereoscopic and privacy modes of operation.
1. A directional backlight comprising:
a waveguide comprising first and second, opposed guide surfaces for guiding light along the waveguide and an input surface extending between the first and second guide surfaces; and
an array of light sources arranged at different input positions along the input surface of the waveguide and arranged to input light into the waveguide, the light sources having light emitting regions that are spaced apart,
the waveguide further comprising a reflective end for reflecting input light from the light sources back along the waveguide, the second guide surface being arranged to deflect the reflected input light through the first guide surface as output light, and the waveguide being arranged to image the light sources so that the output light from the light sources is directed into respective optical windows in output directions that are distributed laterally in dependence on the input positions of the light sources,
wherein the waveguide further comprises at least one surface relief feature formed either on at least one of the first and second guide surfaces in a location adjacent the input surface and intermediate the light emitting regions of the light sources, and/or on the input surface intermediate the light emitting regions of the light sources, and
wherein the surface relief feature is a mechanical fixing feature.
2. The directional backlight according to claim 1 , wherein said location of the surface relief feature is within a region bounded by:
a portion of the input surface intermediate the light emitting regions of a pair of adjacent light sources, and
a pair of intersecting notional lines that extend from the respective edges of the light emitting regions of the pair of light sources that are adjacent the portion of the input surface, to the respective sides of the reflective end that extend between the first and second guide surfaces.
3. The directional backlight according to claim 1 , wherein the mechanical fixing feature is fixed to a further component of the directional backlight.
4. The directional backlight according to claim 3 , further comprising a rear reflector comprising a linear array of reflective facets arranged to reflect light from the light sources, that is transmitted through the plurality of facets second guide surface of the waveguide, back through the waveguide to exit through the first guide surface into said optical windows, the rear reflector being said further component to which the mechanical fixing feature is fixed.
5. The directional backlight according to claim 1 , wherein the input surface is an end of the waveguide opposite to the reflective end.
6. The directional backlight according to claim 1 , wherein the input surface is a side surface of the waveguide extending away from the reflective end.
7. The directional backlight according to claim 1 , wherein the first guide surface is arranged to guide light by total internal reflection and the second guide surface comprises a plurality of light extraction features oriented to direct light guided along the waveguide in directions allowing exit through the first guide surface as the output light and intermediate regions between the light extraction features that are arranged to guide light along the waveguide.
8. The directional backlight according to claim 7 , wherein the second guide surface has a stepped shape in which said light extraction features are facets between the intermediate regions.
9. The directional waveguide according to claim 7 , wherein the light extraction features have positive optical power in a direction between sides of the waveguide that extend between the first and second guide surfaces and between the input end and the reflective end.
10. The directional waveguide according to claim 1 , wherein the reflective end has positive optical power in a direction extending between sides of the waveguide that extend between the first and second guide surfaces and between the input end and the reflective end.
11. A directional display device comprising:
the directional backlight according to claim 1 ; and
a transmissive spatial light modulator arranged to receive the output light from the waveguide and to modulate it to display an image.
12. A directional display apparatus comprising:
the directional display device according to claim 11 ; and
a control system arranged to control the light sources.
13. A directional backlight comprising:
a waveguide comprising first and second, opposed guide surfaces for guiding light along the waveguide and an input surface extending between the first and second guide surfaces; and
an array of light sources arranged at different input positions along the input surface of the waveguide and arranged to input light into the waveguide, the light sources having light emitting regions that are spaced apart,
the waveguide further comprising a reflective end for reflecting input light from the light sources back along the waveguide, the second guide surface being arranged to deflect the reflected input light through the first guide surface as output light, and the waveguide being arranged to image the light sources so that the output light from the light sources is directed into respective optical windows in output directions that are distributed laterally in dependence on the input positions of the light sources,
wherein the waveguide further comprises at least one surface relief feature formed either on at least one of the first and second guide surfaces in a location adjacent the input surface and intermediate the light emitting regions of the light sources, and/or on the input surface intermediate the light emitting regions of the light sources, and
wherein the surface relief feature is an identification or data mark.
14. The directional backlight according to claim 13 , wherein said location of the surface relief feature is within a region bounded by:
a portion of the input surface intermediate the light emitting regions of a pair of adjacent light sources, and
a pair of intersecting notional lines that extend from the respective edges of the light emitting regions of the pair of light sources that are adjacent the portion of the input surface, to the respective sides of the reflective end that extend between the first and second guide surfaces.
15. The directional backlight according to claim 13 , wherein the input surface is an end of the waveguide opposite to the reflective end.
16. The directional backlight according to claim 13 , wherein the input surface is a side surface of the waveguide extending away from the reflective end.
17. The directional backlight according to claim 13 , wherein the first guide surface is arranged to guide light by total internal reflection and the second guide surface comprises a plurality of light extraction features oriented to direct light guided along the waveguide in directions allowing exit through the first guide surface as the output light and intermediate regions between the light extraction features that are arranged to guide light along the waveguide.
18. The directional backlight according to claim 17 , wherein the second guide surface has a stepped shape in which said light extraction features are facets between the intermediate regions.
19. The directional waveguide according to claim 17 , wherein the light extraction features have positive optical power in a direction between sides of the waveguide that extend between the first and second guide surfaces and between the input end and the reflective end.
20. The directional waveguide according to claim 13 , wherein the reflective end has positive optical power in a direction extending between sides of the waveguide that extend between the first and second guide surfaces and between the input end and the reflective end.
21. A directional display device comprising:
the directional backlight according to claim 13 ; and
a transmissive spatial light modulator arranged to receive the output light from the waveguide and to modulate it to display an image.
22. A directional display apparatus comprising:
the directional display device according to claim 21 ; and
a control system arranged to control the light sources.