DIRECTIONAL BACKLIGHTING FOR DISPLAY PANELS

• US 20120200802A1
• Filed: 02/04/2011
• Published: 08/09/2012
• Est. Priority Date: 02/04/2011
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Large, Timothy
• Granted Patent: US 9,201,185 B2
• Time in Patent Office: Days
• US Class Current: 349/62
• CPC Class Codes: G02B 6/0046 Tapered light guide, e.g. wedge-shaped light guide
• 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]

Abstract

Various embodiments are disclosed that relate to display panel backlight systems that output light with a narrower angular intensity distribution than a diffuse backlight. For example, one disclosed embodiment provides a backlight system comprising a wedge-shaped light guide comprising a thin end and a thick end, the thick end of the wedge-shaped light guide comprising a linear reflector with plurality of facets, and wherein the backlight system also comprises a plurality of light sources arranged along the thin end of the wedge-shaped light guide.

Claims

1. A backlight system for a display panel, the backlight system comprising:

a wedge-shaped light guide comprising a thin end and a thick end, the thick end of the wedge-shaped light guide comprising a linear reflector with plurality of facets; and

a plurality of light sources arranged along the thin end of the wedge-shaped light guide.

2. The backlight system of claim 1, wherein the plurality of light sources are configured to be illuminated together.

3. The backlight system of claim 1, wherein the thin end and the thick end of the wedge-shaped light guide have a thickness ratio of 0.8:

1.8.

4. The backlight system of claim 3, wherein the plurality of facets have a height of 0.225 mm and an angle of 17.0 degrees with respect to a plane of the reflector.

5. The backlight system of claim 1, further comprising a plurality of concentrators, wherein each concentrator is disposed optically between a corresponding light source and the wedge-shaped light guide.

6. The backlight system of claim 5, wherein each light source of a first subset of light sources is configured to output light having a narrower emitter angle, and wherein each light source of a second subset of light sources is configured to output light having a wider emitter angle, and further comprising a controller configured to switch between operating the backlight system in a narrow angle mode in which the first subset of light sources are in an on state and operating the backlight system in a wide angle mode in which the second subset of light sources are in an on state.

7. The backlight system of claim 1, further comprising a diffraction grating configured to separate light emitted from the optical wedge into separate colors, and also further comprising a lens array configured to direct diffracted light through color filters of a liquid crystal display panel.

8. The backlight system of claim 5, wherein one or more concentrators each comprises a cylindrical lens.

9. The backlight system of claim 1, further comprising a turning structure disposed on an exit surface of the wedge-shaped light guide and comprising a plurality of facets, wherein angles of the facets vary as a function of facet position.

10. The light guide of claim 1, wherein the wedge-shaped light guide comprises a non-planar exit surface.

17. The display device of claim 2, wherein the plurality of light sources are configured to emit light from the light sources having an angular distribution with a full-width half-maximum of between 40 and 80 degrees.

19. The method of claim 3, further comprising directing light from each light source through a concentrator before injecting the light into the wedge-shaped light guide.

20. The method of claim 19, wherein the plurality of light sources is a first plurality of light sources, and wherein the method further comprises switching the first plurality of light sources off and switching on a second plurality of light sources on upon occurrence of a triggering event, wherein light from each of the second plurality of light sources is injected to the wedge-shaped light guide with a wider angular intensity distribution than light from each of the first plurality of light sources.

11. A display device, comprising:

a modulating image display panel; and

a backlight system configured to backlight the modulating image display panel, the backlight system comprising;

a wedge-shaped light guide comprising a thin end and a thick end, the thick end of the wedge-shaped light guide comprising a linear reflector with plurality of facets;

a plurality of light sources arranged along the thin end of the backlight system and configured to be illuminated together; and

a turning structure disposed on an exit surface of the wedge-shaped light guide to redirect light emitted from the exit surface of the wedge-shaped light guide, the turning structure comprising a plurality of facets each having an angle with respect to a turning structure surface normal, wherein the angles of the facets vary as a function of facet position on the turning structure.

12. The display device of claim 11, wherein the thin end and the thick end of the wedge-shaped light guide have a thickness ratio of 0.8:

1.8.

13. The display device of claim 12, wherein the plurality of facets have a height of 0.225 mm and an angle of 17.0 degrees with respect to a plane of the reflector.

14. The display device of claim 11, further comprising a plurality of concentrators, wherein each concentrator is disposed optically between a corresponding light source and the wedge-shaped light guide.

15. The display device of claim 14, wherein each light source of a first subset of light sources has a corresponding concentrator configured to emit light at a narrower emitter angle, and wherein each light source of a second subset of light sources is configured to emit light at a wider emitter angle.

16. The display device of claim 15, further comprising a controller configured to switch between operating the backlight system in a narrow angle mode in which the first subset of light sources are in an on state and operating the backlight system in a wide angle mode in which the second set of light sources are in an on state.

18. A method of operating a backlit display device, comprising:

illuminating a plurality of light sources to inject light into a thin end of an wedge-shaped light guide at multiple locations along a length of the thin end of the wedge-shaped light guide;

internally reflecting the light via a linear reflector disposed at a thick end of the wedge-shaped light guide;

emitting the light from the wedge-shaped light guide; and

directing the light emitted from the light guide through a modulating display panel to produce a displayed image.