Reducing light leakage and improving contrast ratio performance in FTIR display devices

• US 20070047887A1
• Filed: 08/30/2005
• Published: 03/01/2007
• Est. Priority Date: 08/30/2005
• Status: Active Grant

• Current Assignee: Rambus Delaware
• Original Assignee: Uni-Pixel Displays Incorporated (Uni-Pixel Incorporated)
• Inventors: Selbrede, Martin
• Granted Patent: US 8,509,582 B2
• Time in Patent Office: Days
• US Class Current: 385/129
• CPC Class Codes: G02B 6/0023 provided by one optical element, or plurality thereof, placed between the light guide and the light source, or around the light source

Abstract

An optical noise reduction mechanism for reducing undesired frustration of total internal reflected light. Such optical noise may stem from defects in waveguide construction. Such optical noise may also stem from the difference in refractive index between any cladding layers disposed onto the planar waveguide and the refractive index of the medium (e.g., air) between the light sources and the light insertion surface of the planar waveguide. By interposing a material of appropriate refractive index, either as a thin layer onto the light insertion surface of the waveguide or filling the space between the waveguide and the light source, the planar waveguide becomes more tolerant of geometry errors and cladding layer properties because a safe operating area is established between the unadjusted critical angle of the system and the actual range of ray angles allowed admittance into the waveguide.

Claims

1. A noise reduction mechanism comprising:

a planar waveguide;

a cladding layer disposed onto said planar waveguide; and

a light source separated from said planar waveguide by a noise reduction layer in contact with a side of said planar waveguide, wherein a material of said noise reduction layer in contact with said side of said planar waveguide bears a refractive index selected to optimize noise reduction.

2. The noise reduction mechanism as recited in claim 1, wherein said cladding layer comprises sol-gel.

3. The noise reduction mechanism as recited in claim 1, wherein said cladding layer comprises aerogel.

4. The noise reduction mechanism as recited in claim 1, wherein said refractive index of said noise reduction layer in contact with said side of said planar waveguide matches a refractive index of said cladding layer.

5. The noise reduction mechanism as recited in claim 4, where said noise reduction layer in contact with said side of said planar waveguide comprises aerogel.

6. The noise reduction mechanism as recited in claim 4, where said noise reduction layer in contact with said side of said planar waveguide comprises sol-gel.

7. The noise reduction mechanism as recited in claim 1, wherein said refractive index of said noise reduction layer in contact with said side of said planar waveguide exceeds a refractive index of said cladding layer.

8. The noise reduction mechanism as recited in claim 7, where said noise reduction layer in contact with said side of said planar waveguide comprises aerogel.

9. The noise reduction mechanism as recited in claim 7, where said noise reduction layer in contact with said side of said planar waveguide comprises sol-gel.

10. The noise reduction mechanism as recited in claim 1, wherein said noise reduction layer in contact with said side of said planar waveguide extends from said side of said planar waveguide to said light source such that a light emitted from said light source describes a trajectory that is wholly embedded within said material as said light passes from said light source into said planar waveguide.

11. The noise reduction mechanism as recited in claim 1, wherein said cladding layer includes a plurality of voids, wherein areas of said cladding layer without voids are used to keep other layers superadded on top of said cladding layer at a fixed distance from said planar waveguide.

12. The noise reduction mechanism as recited in claim 11, wherein areas of said cladding layer without voids allow a degree of motional freedom to said superadded layers to move towards and away from said planar waveguide within said plurality of voids.

23. The display system as recited in claim 1, wherein said cladding layer includes a plurality of voids, wherein areas of said cladding layer without voids are used to keep other layers superadded on top of said cladding layer at a fixed distance from said planar waveguide.

24. The display system as recited in claim 23, wherein areas of said cladding layer without voids allow a degree of motional freedom to said superadded layers to move towards and away from said planar waveguide within said plurality of voids.

13. A display system, comprising:

a plurality of pixels on a display, wherein each of said plurality of pixels comprises;

a planar waveguide; and

a cladding layer disposed onto said planar waveguide; and

a light source separated from said planar waveguide by a noise reduction layer in contact with a side of said planar waveguide, wherein a material of said noise reduction layer in contact with said side of said planar waveguide bears a refractive index selected to optimize noise reduction.

14. The display system as recited in claim 13, wherein said cladding layer comprises sol-gel.

15. The display system as recited in claim 13, wherein said cladding layer comprises aerogel.

16. The display system as recited in claim 13, wherein said refractive index of said noise reduction layer in contact with said side of said planar waveguide matches a refractive index of said cladding layer.

17. The display system as recited in claim 16, where said noise reduction layer in contact with said side of said planar waveguide comprises aerogel.

18. The display system as recited in claim 16, where said noise reduction layer in contact with said side of said planar waveguide comprises sol-gel.

19. The display system as recited in claim 13, wherein said refractive index of said noise reduction layer in contact with said side of said planar waveguide exceeds a refractive index of said cladding layer.

20. The display system as recited in claim 19, where said noise reduction layer in contact with said side of said planar waveguide comprises aerogel.

21. The display system as recited in claim 19, where said noise reduction layer in contact with said side of said planar waveguide comprises sol-gel.

22. The display system as recited in claim 13, wherein said noise reduction layer in contact with said side of said planar waveguide extends from said side of said planar waveguide to said light source such that a light emitted from said light source describes a trajectory that is wholly embedded within said material as said light passes from said light source into said planar waveguide.