Directional flat illuminators

• US 10,473,947 B2
• Filed: 12/12/2016
• Issued: 11/12/2019
• Est. Priority Date: 11/19/2010
• Status: Active Grant

• Current Assignee: Reald Spark, LLC
• Original Assignee: Reald Spark, LLC
• Inventors: Robinson, Michael G., Woodgate, Graham John, Harrold, Jonathan
• Primary Examiner(s): Chang, Audrey Y
• Application Number:
  US15/376,264
• Publication Number:
  US 20170160554A1
• Time in Patent Office: 1,065 Days
• Field of Search: 359 34, 362600, 362606, 362615, 385129, 385146, 385147
• CPC Class Codes: G02B 27/0093 with means for monitoring data relating to the user, e.g. head-tracking, eye-tracking
• CPC Class Codes: G02B 30/33 involving directional light or back-light sources
• CPC Class Codes: G02B 30/36 using refractive optical elements, e.g. prisms, in the optical path between the images and the observer
• CPC Class Codes: G02B 6/001 the light being emitted along at least a portion of the lateral surface of the fibre
• CPC Class Codes: G02B 6/0033 Means for improving the coupling-out of light from the light guide
• CPC Class Codes: G02B 6/0038 Linear indentations or grooves, e.g. arc-shaped grooves or meandering grooves, extending over the full length or width of the light guide
• CPC Class Codes: G02B 6/004 Scattering dots or dot-like elements, e.g. microbeads, scattering particles, nanoparticles
• CPC Class Codes: G02B 6/0045 by shaping at least a portion of the light guide
• CPC Class Codes: G02B 6/0046 Tapered light guide, e.g. wedge-shaped light guide
• CPC Class Codes: G02B 6/0048 with stepwise taper
• CPC Class Codes: G02B 6/005 provided by one optical element, or plurality thereof, placed on the light output side of the light guide
• CPC Class Codes: G02B 6/0051 Diffusing sheet or layer
• CPC Class Codes: G02B 6/0055 Reflecting element, sheet or layer
• CPC Class Codes: G02B 6/0068 Arrangements of plural sources, e.g. multi-colour light sources
• CPC Class Codes: G02B 6/0073 Light emitting diode [LED]
• CPC Class Codes: H04N 13/312 the parallax barriers being placed behind the display panel, e.g. between backlight and spatial light modulator [SLM]
• CPC Class Codes: H04N 13/368 for two or more viewers
• CPC Class Codes: H04N 13/398 Synchronisation thereof; Control thereof

Abstract

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.

Claims

1. A directional display comprising:

a light valve, comprising;

a first end at which light provided by an array of illumination elements 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; 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 are curved along the direction in which they are elongated,

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 extraction features are configured to have a cross-sectional profile that allows 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 the plurality of illumination elements to be focused,

wherein the degree of the curvature of the extraction features is configured to cooperate with the curvature of the reflective end 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.

2. The directional display of claim 1, wherein the first end is thinner than the second end.

3. The directional display of claim 1, wherein the guiding features have a wedge angle compared to the first light guiding surface.

4. The directional display of claim 1, wherein the second end is coated with a reflective coating.

5. The directional display of claim 1, wherein the optical axis of the second end is substantially orthogonal to the surface normal of the first light guiding surface.

6. The directional display of claim 1, wherein the orientation of the extraction features varies across the light valve in the first direction.

7. The directional display of claim 1, further comprising a Fresnel lens and a diffuser located to receive light from the light valve.

8. The directional display of claim 7, wherein the Fresnel lens is spherical in form.

9. The directional display of claim 7, wherein the axis of the Fresnel lens is offset relative to the center of the optical valve.

10. The directional display of claim 1, further comprising a vertical diffuser located to receive light from the light valve.

11. The directional display of claim 10, wherein the vertical diffuser further comprises an asymmetric scattering surface.

12. The directional display of claim 1, wherein the density of extraction features at an edge of the light valve is lower than the density of extraction features in a center of the light valve.

13. The directional display of claim 1, wherein the extraction features have a variable slope and height from one another, wherein the slope is adjusted to alter the vertical diffusion characteristics and the height is adjusted to vary the amount of light that is extracted from the light valve.

14. The directional display of claim 1, wherein the height of the extraction features varies across the width of the light valve.

15. The directional display of claim 1, wherein the extraction features have a surface modulation for deflecting light approximately into a set of prescribed horizontal and vertical angles.

16. The directional display of claim 1, further comprising a sensor for detecting a position of an observer in the proximity of viewing windows of the light valve.

17. The directional display of claim 16, wherein the illuminator controller is arranged to control the illumination elements depending on the position of the observer detected by the sensor.

18. The directional display of claim 1, being an observer tracking autostereoscopic display wherein the illuminator controller is arranged to control 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.

19. The direction display of claim 18, 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.

20. A light valve, comprising:

a first end at which light provided by an array of illumination elements 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; 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 are curved along the direction in which they are elongated,

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 extraction features are configured to have a cross-sectional profile that allows 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 the plurality of illumination elements to be focused, wherein the degree of the curvature of the extraction features is configured to cooperate with the curvature of the reflective end to direct focused light into respective viewing windows in the viewing plane.

21. A directional display comprising the light valve of claim 20, and further comprising:

a 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.

22. The light valve of claim 20, wherein the first end is thinner than the second end.

23. The light valve of claim 20, wherein the guiding features have a wedge angle compared to the first light guiding surface.

24. The light valve of claim 20, wherein the density of extraction features at an edge of the light valve is lower than the density of extraction features in a center of the light valve.

25. The light valve of claim 20, wherein the extraction features have a variable slope and height from one another, wherein the slope is adjusted to alter the vertical diffusion characteristics and the height is adjusted to vary the amount of light that is extracted from the light valve.

26. The light valve of claim 20, wherein the height of the extraction features varies across the width of the light valve.

27. The light valve of claim 20, wherein the extraction features have a surface modulation for deflecting light approximately into a set of prescribed horizontal and vertical angles.