LIGHT GUIDES AND BACKLIGHT SYSTEMS INCORPORATING PRISMATIC STRUCTURES AND LIGHT REDIRECTORS

• US 20110205756A1
• Filed: 02/17/2011
• Published: 08/25/2011
• Est. Priority Date: 02/19/2010
• Status: Abandoned Application

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Pixtronix, Incorporated (Qualcomm, Inc.)
• Inventors: Gandhi, Jignesh, Kim, Je Hong
• Application Number:
  US13/029,945
• Publication Number:
  US 20110205756A1
• Time in Patent Office: Days
• US Class Current: 362/607
• CPC Class Codes: G02B 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer
• CPC Class Codes: G02B 6/0061 to provide homogeneous light output intensity

Abstract

Apparatus and method for collecting and directing light from a source via a light guide and modulated display assembly in an efficient manner through the design and use of prismatic optical structures, diffusers and/or light redirectors. The prismatic optical structures may include a plurality of rear-facing prisms and/or front-facing prisms, each with an associated prism apex angle. The prism apex angle for each of the prisms may be selected such that on-axis brightness intensity and/or total optical power extraction of the display are improved.

Claims

1. A display apparatus comprising;

an array of light modulators defining a display surface;

a light guide having front and rear surfaces and a plurality of geometric light redirectors;

a rear-facing plurality of prisms,

a front-facing plurality of prisms, wherein each of the rear-facing and front-facing plurality of prisms is located between the light guide and the display surface, and wherein an apex angle of one of the rear-facing plurality of prisms and the front-facing plurality of prisms is less than or equal to about 75 degrees or greater than or equal to about 105 degrees.

2. The display of claim 1, wherein the front-facing plurality of prisms form a front-facing prism sheet, and the rear-facing plurality of prisms form a rear-facing prism sheet.

3. The display of claim 2, wherein the apex angles of one of the rear-facing prisms and the front-facing prisms are constant across the respective prism sheet.

4. The display of claim 2, wherein the apex angles of one of the rear-facing prisms and the front-facing prisms vary across the respective prism sheet.

5. The display of claim 2, wherein the apex angles of one of the rear-facing prisms and the front-facing prisms are symmetric across the respective prism sheet.

6. The display of claim 2, wherein the apex angles of one of the rear-facing prisms and the front-facing prisms are asymmetric across the respective prism sheet.

7. The display of claim 2, further comprising a diffuser located between the rear-facing and front-facing prism sheets.

8. The display of claim 1, wherein the plurality of front-facing prisms and the plurality of rear-facing prisms form opposing sides of a single prism sheet.

9. The display of claim 1, wherein the front and rear facing prisms are contained entirely within an optical cavity.

10. The display of claim 1, wherein the apex angle of the rear-facing plurality of prisms is between about 105 and 130 degrees.

11. The display of claim 1, wherein the apex angle of the rear-facing plurality of prisms is between about 60 and 75 degrees.

12. The display of claim 1, wherein the apex angle of the front-facing plurality of prisms is between about 105 and 130 degrees.

13. The display of claim 1, wherein the apex angle of the front-facing plurality of prisms is between about 60 and 75 degrees.

14. The display of claim 1, wherein the apex angle of the front-facing plurality of prisms is greater than about 130 degrees.

15. The display of claim 1, wherein the apex angle of the rear-facing plurality of prisms is less than about 60 degrees.

16. The display of claim 1, wherein the light modulators are MEMS light modulators.

17. The display of claim 1, wherein the light modulators are shutter-based light modulators.

18. The display of claim 1, wherein the light modulators are liquid crystal light modulators.

19. The display of claim 1, further comprising a lamp for injecting light into the light guide.

20. The display of claim 1, wherein the apex angle of the rear-facing plurality of prisms is substantially the same as the apex angle of the front-facing plurality of prisms.

21. A method of forming an image using a display apparatus comprising:

providing an array of light modulators, which defines a display surface, in proximity to an illumination system including

a front-facing plurality of prisms,

a rear-facing plurality of prisms, wherein an apex angle of one of the rear-facing plurality of prisms and the front-facing plurality of prisms is less than or equal to about 75 degrees or greater than or equal to about 105 degrees, and

a light guide positioned behind the rear-facing plurality of prisms, the light guide having front and rear surfaces and a plurality of geometric light redirectors formed therein;

providing one or more light sources configured to illuminate the light redirectors,

reflecting light off the plurality of light redirectors to within a useful range of angles about a display axis perpendicular to the display surface; and

redirecting the light reflected into the useful range of angles by the light redirectors towards the display surface, by both of the front-facing plurality of prisms and rear-facing plurality of prisms, such that the reflected light remains within the same useful range of angles.

22. The method of claim 21, wherein the front-facing plurality of prisms form a front-facing prism sheet, and the rear-facing plurality of prisms form a rear-facing prism sheet.