DIFFUSER FOR LIGHT FROM LIGHT SOURCE ARRAY AND DISPLAYS INCORPORATING SAME

• US 20070268461A1
• Filed: 07/31/2007
• Published: 11/22/2007
• Est. Priority Date: 07/27/2004
• Status: Active Grant

• Current Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Original Assignee: Dolby Laboratories Incorporated
• Inventors: WHITEHEAD, Lorne
• Granted Patent: US 7,973,878 B2
• Time in Patent Office: Days
• US Class Current: 353/53
• CPC Class Codes: G02F 1/133603 with LEDs
• CPC Class Codes: G02F 1/133607 the light controlling member including light directing or refracting elements, e.g. prisms or lenses
• CPC Class Codes: G02F 1/13362 providing polarized light, e.g. by converting a polarisation component into another one
• CPC Class Codes: G09F 13/0409 Arrangements for homogeneous illumination of the display surface, e.g. using a layer having a non-uniform transparency arrangements of reflectors G09F13/14
• CPC Class Codes: G09F 9/35 being liquid crystals G09F9/302 takes precedence; liquid crystal materials C09K19/00; liquid crystal panels comprising a number of electrodes in a single cell per se G02F1/13

Abstract

An optical structure placeable between a backlight array of point light sources and a planar display. The structure distributes light emitted by the point light sources to uniformly illuminate the plane of the display, without introducing significant viewing parallax. The emitted light is partially collimated within a preferred angular viewing range, maximizing the display'"'"'s luminance when viewed from the normal direction. The structure is highly reflective, such that a substantial portion of any non-emitted light rays are internally reflected by the structure, increasing the likelihood that those rays will be subsequently emitted by the structure.

Claims

1. A projector comprising:

a mirrored backplate;

a light source comprising a plurality of LEDs of multiple colors in a pattern distribution across the mirrored backplate;

an LED controller configured to send brightness control signals to each LED according to image data;

a dimming modulator configured to modulate light from the light source; and

,

an optical system configured to project an image defined by the brightness controlled LEDs and the dimming modulator onto a screen.

2. A projector according to claim 1 wherein the dimming modulator comprises a dimming controller configured to control an amount of dimming performed by a portion of the dimming modulator based on an estimate of an amount of light projected from the light source onto the portion of the dimming modulator.

3. A projector according to claim 1 wherein the pattern comprises a multiple row by multiple column array of elements.

4. A projector according to claim 3 wherein the elements comprise a subset of the plurality of multiple colored LEDs.

5. A projector according to claim 1 wherein the projector is part of a front-projection system.

6. A projector according to claim 1 wherein the projector is part of a rear projection system and the screen comprises a saw shaped Fresnel lens.

7. A projector according to claim 1 wherein the dimming modulator comprises a set of individually controllable transmissive elements.

8. A projector according to claim 7 wherein the transmissive elements comprise liquid crystals.

9. An optical structure for distributing light emitted by light sources of a plurality of point light sources, the structure comprising:

a reflector having an array of apertures for passing light from the point light sources into the structure; and

a light diffuser for diffusing light which passes through the apertures, the light diffuser anisotropically scattering light that interacts with the light diffuser.

10. An optical structure according to claim 9 comprising an angularly selective light transmitter for partially collimating, within a preferred angular viewing range, light which passes through the light diffuser.

11. An optical structure according to claim 10 comprising a reflective polarizer for polarizing light which passes from the light diffuser to the angularly selective light transmitter.

12. An optical structure according to claim 10 wherein the angularly selective light transmitter selectively emits partially collimated light rays in a direction substantially normal to the planar light distribution structure, and rearwardly reflects a substantial portion of any non-emitted light rays.

13. An optical structure according to claim 9 wherein each of the apertures is sized, shaped and aligned to match the size, shape and alignment of a corresponding one of the point light sources.

14. An optical structure according to claim 9 wherein the reflector comprises a highly reflective outward surface.

15. An optical structure according to claim 14 wherein the outward surface of the reflector is at least partially specularly reflective.

16. An optical structure according to claim 9 wherein the light diffuser has an anisotropic scattering coefficient such that light rays which are substantially parallel to a direction normal to the planar light distribution structure are more intensely scattered than light rays which are substantially perpendicular to a direction normal to the planar light distribution structure.

17. An optical structure according to claim 9 comprising a plurality of layers of a thin, weakly light-scattering sheet material within the diffuser.

18. An optical structure according to claim 11 wherein the reflective polarizer polarizes light rays to match the polarization of a display panel oriented parallel to the angularly selective light transmitter.

19. A display comprising an array of point light sources, a display panel, and an optical structure according to claim 9 disposed between the point light sources and the display panel.

20. A display according to claim 19 wherein the display panel comprises an LCD display panel.