USE OF AN ANGLE-SELECTIVE RETRO-REFLECTOR TO RECAPTURE OFF-STATE ENERGY

• US 20100067086A1
• Filed: 09/15/2008
• Published: 03/18/2010
• Est. Priority Date: 09/15/2008
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Khan, Sajjad A.
• Granted Patent: US 7,826,121 B2
• Time in Patent Office: Days
• US Class Current: 359/239
• CPC Class Codes: G02B 26/0833 the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD G02B26/0825 takes precedence; micromechanical devices in general B81B
• CPC Class Codes: G02B 5/12 Reflex reflectors
• CPC Class Codes: H04N 9/3161 using laser light sources using laser beams scanning the display screen H04N9/3129

Abstract

Provided is a method for using a display system. The method, in one embodiment, includes directing a light beam from a light source to an array of individually addressable pixels of a spatial light modulator. The method further includes modulating the light beam into a first portion of light using a first addressable pixel, and a second portion of light using a second addressable pixel. Thereafter, the method includes directing the first portion of light having a first incident angle and the second portion of light having a second different incident angle toward an angle-selective retro-reflector, the angle-selective retro-reflector configured to transmit the first portion of light onto a display target, and reflect the second portion of light back toward the second addressable pixel. Additionally, the method includes recycling the reflected second portion of light to the pixels of the spatial light modulator.

Claims

1. A method for use in a display system that employs a spatial light modulator that comprises an array of individually addressable pixels, the method comprising:

directing a light beam from a light source to an array of individually addressable pixels of a spatial light modulator;

modulating the light beam into a first portion of light using a first addressable pixel, and a second portion of light using a second addressable pixel;

directing the first portion of light having a first incident angle and the second portion of light having a second different incident angle toward an angle-selective retro-reflector, the angle-selective retro-reflector configured to transmit the first portion of light onto a display target, and reflect the second portion of light back toward the second addressable pixel; and

recycling the reflected second portion of light to the pixels of the spatial light modulator.

2. The method of claim 1 wherein directing the first portion of light and the second portion of light toward an angle-selective retro-reflector includes directing toward a passive angle-selective retro-reflector.

3. The method of claim 2 wherein the passive angle-selective retro-reflector comprises a stack of wavelength tuned volume Bragg gratings, a stack of wavelength tuned holographic optical elements, or a z-chirped volume Bragg grating.

4. The method of claim 2 wherein the angle-selective retro-reflector is positioned on a front window of the spatial light modulator.

5. The method of claim 2 wherein the angle-selective retro-reflector is positioned on individual micromirrors or pixels of the spatial light modulator.

6. The method of claim 1 wherein directing the first portion of light and the second portion of light toward an angle-selective retro-reflector includes directing toward a switchable angle-selective retro-reflector.

7. The method of claim 1 wherein the switchable angle-selective retro-reflector comprises a single active acousto-optic Bragg grating, a phased array of active acousto-optic Bragg gratings, a single active polymer-dispersed liquid crystal grating, or multiple active polymer-dispersed liquid crystal gratings.

8. The method of claim 1 wherein a depth of focus of the light beam should be at least about twice a distance between the spatial light modulator and the angle-selective retro-reflector.

9. The method of claim 1 wherein recycling includes capturing the second portion of light using an optical integrator that comprises a substantially open end.

10. The method of claim 9 wherein the optical integrator is at a location such that an illumination field of the second portion of light at said open end of the optical integrator has an area that is substantially equal to or less than the area of said open end.

11. The method of claim 9 wherein the optical integrator comprises an opening formed on a side wall of the end of the optical integrator, and wherein the side wall has an interior surface that is covered by a reflective layer for reversing a propagation direction of the second portion of light inside the optical integrator.

12. The method of claim 9 wherein the optical integrator is positioned such that the opening in the side wall is aligned to the light beam from the light source.

13. The method of claim 1 wherein the spatial light modulator comprises a digital micromirror device having an array of individually addressable mirrors.

14. The method of claim 1 wherein the angle-selective retro-reflector is located in the spatial light modulator or on a front window of the spatial light modulator.

15. A display system, comprising:

a light source configured to provide a light beam;

a spatial light modulator located in optical communication with the light source and having an array of addressable pixels, wherein a first addressable pixel is configured to modulate the light beam into a first portion of light having a first incident angle, and a second addressable pixel is configured to modulate the light beam into a second portion of light having a second different incident angle;

an angle-selective retro-reflector located proximate the spatial light modulator and configured to receive the first portion and the second portion, wherein the angle-selective retro-reflector is configured to transmit the first portion of light onto a display target, and reflect the second portion of light back toward the second addressable pixel;

an OFF-state recycling mechanism placed in optical communication with the spatial light modulator, the recycling mechanism configured to capture the reflected second portion of light and redirect it back toward the spatial light modulator.

16. The system of claim 15 wherein the angle-selective retro-reflector is a passive angle-selective retro-reflector selected from the group consisting of:

a stack of wavelength tuned volume Bragg gratings;

a stack of wavelength tuned holographic optical elements; and

a z-chirped volume Bragg grating.

17. The system of claim 15 wherein the angle-selective retro-reflector is a switchable angle-selective retro-reflector selected from the group consisting of:

a single active acousto-optic Bragg grating;

a phased array of acousto-optic Bragg gratings;

a single active polymer-dispersed liquid crystal grating; and

multiple active polymer-dispersed liquid crystal gratings.

18. The system of claim 15 wherein a distance between the spatial light modulator and the angle-selective retro-reflector should be about one half or less of a depth of focus of the light beam.

19. The system of claim 15 wherein the OFF-state recycling mechanism comprises an optical integrator having a substantially open end.

20. The system of claim 19 wherein the optical integrator comprises an opening formed on a side wall of the end of the optical integrator, and wherein the side wall has an interior surface that is covered by a reflective layer for reversing a propagation direction of the second portion of light inside the optical integrator.

21. The system of claim 19 wherein the optical integrator is positioned such that the opening in the side wall is aligned to the light beam from the light source.

22. The system of claim 15 wherein the spatial light modulator comprises a digital micromirror device having an array of individually addressable mirrors.

23. The system of claim 15 wherein the first incident angle ranges from about zero to about 8 degrees from the surface normal of the angle-selective retro-reflector, and wherein the second different incident angle ranges from about 24.0 degrees to about 80.0 degrees as measured from the surface normal of the angle-selective retro-reflector.

24. The system of claim 15 wherein the light source comprises at least one laser light source.

25. The system of claim 15 wherein the spatial light modulator and the angle-selective retro-reflector are contained within a single package.

26. The system of claim 15 wherein the angle-selective retro-reflector is positioned on a front window of the spatial light modulator.

27. The system of claim 15 wherein the angle-selective retro-reflector is positioned on individual micromirrors or pixels of the spatial light modulator.