Directional flat illuminators
View Patent ↗Disclosed is an optical valve or light valve for providing large area collimated illumination from localized light sources, and system and method thereof for 2D, 3D, and/or autosteroscopic displays. An optical valve may include a stepped structure, in which the steps include separated extraction features which may be optically hidden to light propagating in a first direction. Light propagating in a second direction may be refracted, diffracted, or reflected by the features to provide illumination beams exiting from the top surface of the optical valve. Such controlled illumination may provide for efficient, multi-user autostereoscopic displays as well as improved 2D display functionality.
1. An optical display, comprising:
a light valve, comprising:
a first end at which light may enter the light valve and propagate in a first direction;
a second end that is a reflective surface arranged to redirect light propagating in said first direction to propagate in a second direction back toward the first end, wherein the second end is a concave, curved reflective surface, or a Fresnel equivalent of a concave, curved reflective surface;
a first light guiding surface extending between the first and second ends, wherein the first light guiding surface is substantially planar; and
a second light guiding surface, extending between the first and second ends opposite the first light guiding surface, further comprising a plurality of guiding features and a plurality of elongate extraction features that have a curved cross-sectional profile and are curved along the direction in which they are elongated, wherein the extraction features and the guiding features are connected to and alternate with one another respectively, further wherein the plurality of extraction features allow light to pass substantially without loss when the light is propagating in said first direction and further wherein the curved cross-sectional profile of the extraction features allow light to reflect and exit the light valve through the first guide surface towards a viewing plane when the light is propagating in said second direction and further wherein the curvature of the extraction features along the direction in which the extraction features are elongated causes the light from a plurality of illumination elements to be focused, whereby the curved cross-sectional profile and the curvature of the extraction features and the curvature of the reflective end cooperate to direct focused light into respective viewing windows in the viewing plane, and further wherein the plurality of illumination elements are configured to provide light into the light valve;
a transmissive spatial light modulator arranged to be illuminated by the light valve; and
an illuminator controller for controlling the illumination elements.
2. An optical display according to claim 1 , wherein the plurality of illumination elements are an addressable array of LEDs.
3. An optical display according to claim 1 , further comprising a sensor for detecting a position of an observer in the proximity of viewing windows of the light valve.
4. An optical display according to claim 3 , wherein the illuminator controller is arranged to control the illumination elements depending on the position of the observer detected by the sensor.
5. An optical display according to claim 1 , being an observer tracking autostereoscopic display wherein the illuminator controller is arranged to control the a first set of illumination elements corresponding to a first viewing window to provide light in a first illumination phase, and to control a second set of illumination elements corresponding to a second viewing window to provide light in a second illumination phase.
6. An optical display according to claim 5 , wherein the first illumination phase corresponds to a left eye image on a display, and the second illumination phase corresponds to a right eye image on the display.
7. An optical display according to claim 1 , wherein the second light guiding surface has a stepped structure comprising of the plurality of elongate extraction features, and the plurality of guiding features connecting respective extraction features.
8. An optical display according to claim 1 , wherein the extraction features allow light to exit the light valve through the first light guiding surface.
9. An optical display according to claim 1 , wherein the light valve is arranged to direct light entering the light valve from illumination elements into viewing windows.
10. An optical display according to claim 1 , further comprising a Fresnel lens located to receive light from first light guiding surface of the light valve.
11. An optical display according to claim 1 , further comprising a vertical diffuser located to receive light from the first light guiding surface of the light valve.
12. An optical display according to claim 11 , wherein the vertical diffuser comprises an asymmetric scattering surface.
13. An optical display according to claim 1 , wherein the first end is thinner than the second end.
14. A directional di splay comprising:
a light valve for guiding light;
an array of illumination elements configured to input light into the light valve in a first direction,
the light valve comprising:
a first light guiding surface;
a second light guiding surface, opposite the first light guiding surface; and
a reflective end arranged to redirect light propagating in said first direction back through the light valve in a second direction, wherein the reflective end is a concave, curved reflective surface, or a Fresnel equivalent of a concave, curved reflective surface,
the second light guiding surface comprising a plurality of guiding features and a plurality of elongate extraction features that have a curved cross-sectional profile and are curved along the direction in which they are elongated, wherein the extraction features and the guiding features are connected to and alternate with one another respectively, wherein the plurality of extraction features allow light to pass substantially without loss when the light is propagating in the first direction, and further wherein the curved cross-sectional profile of the extraction features allow light to reflect and exit the light valve through the first guide surface towards a viewing plane when the light is propagating in the second direction, and wherein the curvature of the extraction features along the direction in which the extraction features are elongated causes the light from the illumination elements to be focused, whereby the curved cross-sectional profile and the curvature of the extraction features and the curvature of the reflective end cooperate to direct focused light into respective viewing windows in the viewing plane;
a transmissive spatial light modulator arranged to be illuminated by the light exiting the light valve; and
an illuminator controller arranged to control which illumination elements are illuminated.