Wide angle imaging directional backlights
First Claim
1. A directional waveguide comprising:
- an input end;
first and second opposed, laterally extending guide surfaces for guiding light along the waveguide; and
a reflective end facing the input end for reflecting the input light 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 direct the output light into optical windows in output directions that are distributed in a lateral direction in dependence on the input position of the input light,wherein the reflective end is a Fresnel reflector comprising alternating reflective facets and draft facets, each reflective facet having a plurality of convex, curved sub-facets, the reflective facets providing the Fresnel reflector with positive optical power laterally toward the input end of the waveguide.
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Accused Products
Abstract
An imaging directional backlight apparatus including a waveguide, a light source array, for providing large area directed illumination from localized light sources. The waveguide may include a stepped structure, in which the steps may further include extraction features optically hidden to guided light, propagating in a first forward direction. Returning light propagating in a second backward direction may be refracted, diffracted, or reflected by the features to provide discrete illumination beams exiting from the top surface of the waveguide. In operation, luminance streaks and bright illumination regions may be formed due to undesirable imaging characteristics from the structure of the Fresnel mirror. Fresnel mirror draft facets and reflective facet microstructures are provided that achieve reduction of visibility of light streaks and bright illumination regions.
355 Citations
11 Claims
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1. A directional waveguide comprising:
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an input end; first and second opposed, laterally extending guide surfaces for guiding light along the waveguide; and a reflective end facing the input end for reflecting the input light 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 direct the output light into optical windows in output directions that are distributed in a lateral direction in dependence on the input position of the input light, wherein the reflective end is a Fresnel reflector comprising alternating reflective facets and draft facets, each reflective facet having a plurality of convex, curved sub-facets, the reflective facets providing the Fresnel reflector with positive optical power laterally toward the input end of the waveguide. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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Specification