Stepped waveguide autostereoscopic display apparatus with a reflective directional element
View Patent ↗An autostereoscopic display apparatus may include a stepped waveguide, optical elements, and one or more reflective imaging and/or directional elements. These elements may be arranged to return light from the stepped waveguide into an array of viewing windows. Such elements can be used to achieve observer tracking autostereoscopic display for landscape and portrait modes of operation. System thickness and cost may be reduced and system brightness can be increased or low operating power modes may be achieved.
1. A display apparatus comprising:
a light directing device 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, the waveguide having first and second, opposed guide surfaces for guiding light forwards and back along the waveguide, wherein the second guide surface has a plurality of light extraction features facing the reflective end and inclined to reflect the light guided back through the waveguide from the reflective end in directions allowing exit through the first guide surface, the light extraction features being arranged to direct input light from different input positions across the input end in directions that are dependent on said input position; and
a reflective element arranged to reflect the light exiting the first guide surface back through the waveguide to exit through the second guide surface;
an array of light sources at different positions across the input end of the waveguide;
a control system arranged to selectively operate the light sources so that the light extraction features direct the input light from a selectively operated light source into a corresponding one of a plurality of viewing windows having different positions; and
a transmissive spatial light modulator extending across the second guide surface of the waveguide for modulating the light exiting therethrough.
2. A display apparatus according to claim 1 , being an autostereoscopic display apparatus, wherein the control system is arranged to control the spatial light modulator to display temporally multiplexed left and right eye images and synchronously to operate the light sources to direct light into viewing windows in positions corresponding to the left and right eyes of an observer.
3. A display apparatus according to claim 2 , further comprising a sensor system arranged to detect the position of an observer relative to the display device, the control system to direct the displayed images into viewing windows in positions corresponding to the left and right eyes of the observer, in dependence on the detected position of the observer.
4. A display apparatus according to claim 1 , wherein the reflective element comprises a converging Fresnel mirror.
5. A display apparatus according to claim 1 , wherein the reflective element comprises a concave mirror array.
6. A display apparatus according to claim 1 , wherein the concave mirror array is aligned with the extraction features.
7. A display apparatus according to claim 3 , wherein
the spatial light modulator comprises an array of pixels arranged in an aperture with a shape having two perpendicular axes of mirror symmetry,
the viewing windows extend at an angle in a range from 25 to 65 degrees relative to one of said axes of the shape of the aperture,
the sensor system is further arranged to detect the orientation of the view of the observer, and
the control system is arranged to direct the displayed images into the viewing windows in positions corresponding to the left and right eyes of the observer, in dependence on the detected orientation of the view, as well as the detected position of the observer.
8. A display apparatus according to claim 7 , wherein said range is from 30 to 60 degrees, from 35 to 55 degrees, or from 40 to 50 degrees.
9. A display apparatus according to claim 7 , wherein the sensor system comprises an observer tracking system arranged to detect the position of an observer in two dimensions across the display device and an orientation sensor arranged to detect the orientation of the view of the observer.
10. An autostereoscopic display apparatus, comprising:
a display apparatus comprising:
a light directing device 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, the waveguide having first and second, opposed guide surfaces for guiding light forwards and back along the waveguide, wherein the second guide surface has a plurality of light extraction features facing the reflective end and inclined to reflect the light guided back through the waveguide from the reflective end in directions allowing exit through the first guide surface, the light extraction features being arranged to direct input light from different input positions across the input end in directions that are dependent on said input position; and
a reflective element arranged to reflect the light exiting the first guide surface back through the waveguide to exit through the second guide surface; and
an array of light sources at different positions across the input end of the waveguide; and
a control system arranged to selectively operate the light sources to direct light into a selectable one of a plurality of viewing windows having different positions;
a transmissive spatial light modulator extending across the second guide surface of the waveguide for modulating the light exiting therethrough, wherein the spatial light modulator comprises an array of pixels arranged in an aperture with a shape having two perpendicular axes of mirror symmetry, the viewing windows extending at an angle in a range from 25 to 65 degrees relative to one of said axes of the shape of the aperture;
a sensor system arranged to detect the position of an observer relative to the display device and to detect the orientation of the view of the observer, wherein the control system is arranged to control the spatial light modulator to display temporally multiplexed left and right eye images and synchronously to operate the light sources so that the light extraction features direct the input light from the operated light sources into corresponding viewing windows in positions corresponding to the left and right eyes of an observer, in dependence on the detected position of the observer and in dependence on the detected orientation of the view;
further wherein the waveguide is oriented with respect to the spatial light modulator with the optical axis of the waveguide extending parallel or perpendicular to said axis of the shape of the aperture, and
said reflective element is arranged to rotate the viewing windows around the normal to the spatial light modulator.
11. An autostereoscopic display apparatus according to claim 10 , wherein said shape of the aperture is rectangular and the waveguide is oriented with respect to the spatial light modulator with the optical axis of the waveguide extending parallel to the major axis of the rectangular shape of the aperture.
12. An autostereoscopic display apparatus according to claim 10 , wherein said reflective element is a linear array of pairs of reflective corner facets, the reflective corner facets of each pair being inclined relative to the normal to the spatial light modulator in opposite senses in a plane containing the normal to the spatial light modulator and at a non-zero angle to the optical axis of the waveguide.
13. An autostereoscopic display apparatus according to claim 10 , wherein said shape of the aperture is rectangular.
14. A display apparatus according to claim 1 , wherein the first guide surface is substantially planar.
15. A display apparatus according to claim 1 , wherein the regions of the second guide surface between the light extraction features are substantially planar.
16. A display apparatus according to claim 1 , further comprising a sensor system arranged to detect the position of an observer relative to the display device, the control system being arranged to direct the displayed images into viewing windows in positions in dependence on the detected position of the observer.
17. A display apparatus according to claim 16 , wherein
the spatial light modulator comprises an array of pixels arranged in an aperture with a shape having two perpendicular axes of mirror symmetry,
the viewing windows extend at an angle in a range from 25 to 65 degrees relative to one of said axes of the shape of the aperture,
the sensor system is further arranged to detect the orientation of the view of the observer, and
the control system is arranged to direct the displayed images into the viewing windows in positions in dependence on the detected orientation of the view, as well as the detected position of the observer.
18. A display apparatus according to claim 17 , wherein said shape of the aperture is rectangular and the waveguide is oriented with respect to the spatial light modulator with the optical axis of the waveguide extending parallel to the major axis of the rectangular shape of the aperture.
19. A display apparatus according to claim 17 , wherein said range is from 30 to 60 degrees, from 35 to 55 degrees, or from 40 to 50 degrees.
20. A display apparatus according to claim 17 , wherein
the waveguide is oriented with respect to the spatial light modulator with the optical axis of the waveguide extending parallel or perpendicular to said axis of the shape of the aperture, and
said reflective element is arranged to rotate the viewing windows around the normal to the spatial light modulator.
21. A display apparatus according to claim 20 , wherein said reflective element is a linear array of pairs of reflective corner facets, the reflective corner facets of each pair being inclined relative to the normal to the spatial light modulator in opposite senses in a plane containing the normal to the spatial light modulator and at a non-zero angle to the optical axis of the waveguide.
22. A display apparatus according to claim 1 , wherein said reflective element is arranged to rotate the viewing windows around the normal to the spatial light modulator.
23. A display apparatus according to claim 22 , wherein said reflective element is a linear array of pairs of reflective corner facets, the reflective corner facets of each pair being inclined relative to the normal to the spatial light modulator in opposite senses in a plane containing the normal to the spatial light modulator and at a non-zero angle to the optical axis of the waveguide.