Wide angle imaging directional backlights
First Claim
1. A directional backlight apparatus comprising:
- a waveguide extending between an input end for receiving input light and a reflective end for reflecting the input light back through the waveguide;
an array of light sources disposed at different input positions in a lateral direction across the same input end of the waveguide, the waveguide having first and second, opposed guide surfaces extending between the input end and the reflective end for guiding light forwards and back along the waveguide, the waveguide being arranged to reflect input light from light sources at the different input positions across the input end after reflection from the reflective end into respective optical windows in output directions distributed in the lateral direction in dependence on the input positions; and
a control system arranged to selectively operate the light sources to direct light into selectable viewing windows at different locations and comprising at least one of the optical windows,wherein the reflective end converges the reflected light such that reflected light from light sources that are offset from the optical axis of the waveguide fails to illuminate outer portions of the waveguide,the waveguide further comprises sides, extending between the input end and the reflective end and between the guiding surfaces, that are planar surfaces arranged to reflect light from the light sources, andthe control system being arranged, on selective operation of a first light source to direct light into a first of the viewing windows, to simultaneously operate a second light source that directs light into the first of the viewing windows, wherein the light of the second light source is reflected by the reflective end and then by a side of the waveguide into the outer portion of the waveguide that fails to be illuminated by the first light source,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 reflect light guided through the waveguide in directions allowing exit through the first guide surface as the output light,wherein the light extraction features are facets of the second guide surface, andwherein the second guide surface has a stepped shape comprising said facets and intermediate regions between the facets that are arranged to direct light through the waveguide without extracting the light.
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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. Viewing windows are formed through imaging individual light sources and hence defines the relative positions of system elements and ray paths. The uncorrected system creates non-illuminated void portions when viewed off-axis preventing uniform wide angle 2D illumination modes. The system may be corrected to remove this non-uniformity at wide angles through the introduction of additional sources away from the system'"'"'s object plane, additional imaging surfaces, and/or by altering ray paths.
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Citations
15 Claims
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1. A directional backlight apparatus comprising:
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a waveguide extending between an input end for receiving input light and a reflective end for reflecting the input light back through the waveguide; an array of light sources disposed at different input positions in a lateral direction across the same input end of the waveguide, the waveguide having first and second, opposed guide surfaces extending between the input end and the reflective end for guiding light forwards and back along the waveguide, the waveguide being arranged to reflect input light from light sources at the different input positions across the input end after reflection from the reflective end into respective optical windows in output directions distributed in the lateral direction in dependence on the input positions; and a control system arranged to selectively operate the light sources to direct light into selectable viewing windows at different locations and comprising at least one of the optical windows, wherein the reflective end converges the reflected light such that reflected light from light sources that are offset from the optical axis of the waveguide fails to illuminate outer portions of the waveguide, the waveguide further comprises sides, extending between the input end and the reflective end and between the guiding surfaces, that are planar surfaces arranged to reflect light from the light sources, and the control system being arranged, on selective operation of a first light source to direct light into a first of the viewing windows, to simultaneously operate a second light source that directs light into the first of the viewing windows, wherein the light of the second light source is reflected by the reflective end and then by a side of the waveguide into the outer portion of the waveguide that fails to be illuminated by the first light source, 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 reflect light guided through the waveguide in directions allowing exit through the first guide surface as the output light, wherein the light extraction features are facets of the second guide surface, and wherein the second guide surface has a stepped shape comprising said facets and intermediate regions between the facets that are arranged to direct light through the waveguide without extracting the light. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A display apparatus comprising:
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a directional backlight apparatus comprising; a waveguide extending between an input end for receiving input light and a reflective end for reflecting the input light back through the waveguide; an array of light sources disposed at different input positions in a lateral direction across the same input end of the waveguide, the waveguide having first and second, opposed guide surfaces extending between the input end and the reflective end for guiding light forwards and back along the waveguide, the waveguide being arranged to reflect input light from light sources at the different input positions across the input end after reflection from the reflective end into respective optical windows in output directions distributed in the lateral direction in dependence on the input positions; and a control system arranged to selectively operate the light sources to direct light into selectable viewing windows at different locations and comprising at least one of the optical windows, wherein the reflective end converges the reflected light such that reflected light from light sources that are offset from the optical axis of the waveguide fails to illuminate outer portions of the waveguide, the waveguide further comprises sides, extending between the input end and the reflective end and between the guiding surfaces, that are planar surfaces arranged to reflect light from the light sources, and the control system being arranged, on selective operation of a first light source to direct light into a first of the viewing windows, to simultaneously operate a second light source that directs light into the first of the viewing windows, wherein the light of the second light source is reflected by the reflective end and then by a side of the waveguide into the outer portion of the waveguide that fails to be illuminated by the first light source; and a transmissive spatial light modulator extending across the directional backlight apparatus for modulating the light output therefrom, 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 reflect light guided through the waveguide in directions allowing exit through the first guide surface as the output light, wherein the light extraction features are facets of the second guide surface, and wherein the second guide surface has a stepped shape comprising said facets and intermediate regions between the facets that are arranged to direct light through the waveguide without extracting the light. - View Dependent Claims (9, 10, 11, 12)
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13. A display apparatus comprising:
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a display device including;
a waveguide extending between an input end for receiving input light and a reflective end for reflecting the input light back through the waveguide;
an array of light sources disposed at different input positions in a lateral direction across the same input end of the waveguide, the waveguide having first and second, opposed guide surfaces extending between the input end and the reflective end for guiding light forwards and back along the waveguide, the waveguide being arranged to reflect input light from light sources at the different input positions across the input end after reflection from the reflective end into respective optical windows in output directions distributed in the lateral direction in dependence on the input positions; anda transmissive spatial light modulator extending across the waveguide for modulating the light output therefrom, wherein the spatial light modulator extends across only part of the area of the waveguide; and a control system arranged to selectively operate the light sources to direct light into selectable viewing windows at different locations and comprising at least one of the optical windows, 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 reflect light guided through the waveguide in directions allowing exit through the first guide surface as the output light, wherein the light extraction features are facets of the second guide surface, and wherein the second guide surface has a stepped shape comprising said facets and intermediate regions between the facets that are arranged to direct light through the waveguide without extracting the light. - View Dependent Claims (14, 15)
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Specification