Optical microstructures for light extraction and control

• US 20070172171A1
• Filed: 01/24/2006
• Published: 07/26/2007
• Est. Priority Date: 01/24/2006
• Status: Active Grant

• Current Assignee: Rambus Delaware
• Original Assignee: Uni-Pixel Displays Incorporated (Uni-Pixel Incorporated)
• Inventors: King, Carey, Van Ostrand, Dan, Gobeli, Garth
• Granted Patent: US 7,486,854 B2
• Time in Patent Office: Days
• US Class Current: 385/31
• CPC Class Codes: G02B 6/00 Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
• CPC Class Codes: G02B 6/122 Basic optical elements, e.g. light-guiding paths
• CPC Class Codes: G02B 6/125 Bends, branchings or intersections
• CPC Class Codes: G02B 6/2852 using tapping light guides arranged sidewardly, e.g. in a non-parallel relationship with respect to the bus light guides (light extraction or launching through cladding, with or without surface discontinuities, bent structures)
• CPC Class Codes: G02B 6/351 involving stationary waveguides with moving interposed optical elements G02B6/3538 takes precedence; interposed waveguides G02B6/3502
• CPC Class Codes: G09G 3/3473 based on light coupled out of a light guide, e.g. due to scattering, by contracting the light guide with external means

Abstract

The application of microstructures which improve the quality of light available to the viewer of an optical display system, or any display which works on the concept of moving one surface into direct contact or close proximity of a light guide to extract light through frustrated total internal reflection. Optical microstructures are introduced on one or both of the surfaces of the active layer to enhance its performance. Since the active layer has both an input and an output function, means for enhancing both are presented. The input function to the active layer occurs on the internal surface, so this is where the present invention adds a collector-coupler, a means for facilitating the migration of light from the waveguide into the active layer. The output function occurs on the external surface, where the present invention adds a collimator, a means for both increasing the probability that a light wave will be released from the active layer, and improving the apparent intensity by redirecting light waves so that more of them reach the viewer. Compound microlenses on the internal surface of the active layer can serve as both collector-couplers and collimators, substantially improving light extraction from the light guide and light distribution to the viewer. Depositing a reflective or colored material in the interstitial spaces between these compound microlenses improves the contrast ratio and mitigate pixel cross-talk. The opaque material can be conductive for use in actuating the display.

Claims

1. A pixel, comprising:

a light guide;

an active layer; and

a first set of collector-coupler features on said internal surface of said active layer, wherein said first set of collector-coupler features is configured to interact with light waves that approach a vicinity of said light guide in order to increase a probability of light waves exiting said light guide and entering said active layer.

2. A pixel as recited in claim 1, further comprising:

a second set of collector-coupler features on said internal surface of said active layer interspersed with said first set of collector-coupler features, wherein each of said second set of collector-coupler features is longer than each of said first set of collector-coupler features.

3. The pixel as recited in claim 2, wherein when a surface of one of said second set of collector-coupler features comes in contact with said light guide, said surface of said one of said second set collector-coupler features is compressed.

4. The pixel as recited in claim 2, further comprising:

a layer of highly compliant material under said first set of collector-coupler features, wherein said layer of highly compliant material provides a restorative force to overcome stiction between said first set of collector-coupler features and said light guide.

5. The pixel as recited in claim 1, wherein said first set of collector-coupler features are angled.

6. The pixel as recited in claim 2, wherein said first set of collector-coupler features comes into contact with said light guide, said first set of collector-coupler features are elastically deformed in such a manner as to build potential energy.

7. The pixel as recited in claim 2, wherein upon entering an off state after completion of said on state, said first set of collector-coupler features release said potential energy.

8. The pixel as recited in claim 1, further comprising:

collimator features on an external surface of said active layer, wherein said collimator features are configured to interact with light waves that approach a vicinity of an interface between said active layer'"'"'s external surface and said collimator features in order to increase a probability of light waves exiting said external surface of said active layer and entering said collimator features.

9. The pixel as recited in claim 1, wherein optical properties of said collimator features are selected so as to redirect waves that would otherwise leave said active layer'"'"'s external surface to leave said collimator features'"'"'external surface more nearly in a direction perpendicular to said external surface.

10. The pixel as recited in claim 1, wherein optical properties of each collector-coupler of said set of collector-coupler features are selected such that light entering the collector-coupler from the light guide will contact a side boundary of the collector-coupler under conditions sufficient for total internal reflection within the collector-coupler before said light contacts a boundary between said collector-coupler and said active layer.

11. The pixel as recited in claim 1, wherein a material is disposed interstitially between the collector-coupler features of said first set of collector-coupler features, and wherein said material is color absorbing or reflective.

12. The pixel as recited in claim 11, wherein said material comprises an electrical conductor.

27. The pixel as recited in claim 1, wherein the first set of collector-coupler features comprises a plurality of compound microlens.

28. The pixel as recited in claim 1, wherein a shape of the compound microlens is configured so that light coupled into a first end of the compound microlens will contact an internal side of the compound microlens under conditions sufficient for total internal reflection within the compound microlens before it exits from a second end of the compound microlens that is parallel to and opposite of the first end of the compound microlens.

29. The pixel as recited in claim 27, wherein the compound microlens comprises a pyramidal frustrum.

30. The pixel as recited in claim 27, wherein the compound microlens comprises a conical frustrum.

31. The pixel as recited in claim 27, wherein the compound microlens comprises a compound frustrum.

37. The display as recited in claim 1, wherein the active layer is configured to physically move towards the light guide, when the pixel is activated to emit light, in a manner so that at least some of the first set of collector-coupler features contact the light guide.

39. The pixel as recited in claim 37, wherein, when the pixel is inactivated to emit light, the active layer is positioned so that the first set of collector-coupler features are not in contact with the light guide.

13. A display system, comprising:

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

a light guide;

an active layer; and

a first set of collector-coupler features on said internal surface of said active layer, wherein said first set of collector-coupler features is configured to interact with light waves that approach a vicinity of said light guide in order to increase a probability of light waves exiting said light guide and entering said active layer.

14. The display system as recited in claim 13, wherein each of said plurality of pixels comprising:

a second set of collector-coupler features on said internal surface of said active layer interspersed with said first set of collector-coupler features, wherein each of said second set of collector-coupler features is longer that each of said first set of collector-coupler features.

15. The display system as recited in claim 13, wherein when a surface of one of said second set of collector-coupler features comes in contact with said light guide, said surface of said one of said second set of collector-coupler features is compressed.

16. The display system as recited in claim 14, wherein each of said plurality of pixels comprises:

a layer of compliant material under said first and said second set of collector-coupler features, wherein said layer of compliant material provides a restorative force to overcome stiction.

17. The display system as recited in claim 13, wherein said first set of collector-coupler features are angled at their ends.

18. The display system as recited in claim 17, wherein when said first set of collector-coupler features comes into contact with said light guide, said first set of collector-coupler features are elastically deformed in such a manner as to build potential energy.

19. The display system as recited in claim 18, wherein upon entering an off state after completion of said on state, said first set of collector-coupler features release said potential energy.

20. The display system as recited in claim 13, wherein each of said plurality of pixels comprises:

collimator features on an external surface of said active layer, wherein said collimator features are configured to interact with light waves that approach a vicinity of an interface between said active layer'"'"'s external surface and said collimator features in order to increase a probability of light waves exiting said external surface of said active layer and entering said collimator feature.

21. The display system as recited in claim 13, wherein optical properties of each collector-couple of said first set of collector-coupler features are selected such that light entering the collector-couple from the light guide will contact a side boundary of the collector-couple under conditions sufficient for total internal reflection within the collector-couple before said light contacts a boundary between said collector-couple and said active layer.

22. The display system as recited in claim 21, wherein a material is disposed interstitially between the collector-couple features of said first set of collector-couple features, and wherein said material is color absorbing or reflective.

23. The display system as recited in claim 22, wherein said opaque material comprises an electrical conductor.

32. The display system as recited in claim 13, wherein the first set of collector-coupler features comprises a plurality of compound microlens.

33. The display system as recited in claim 13, wherein a shape of the compound microlens is configured so that light coupled into a first end of the compound microlens will contact an internal side of the compound microlens under conditions sufficient for total internal reflection within the compound microlens before it exits from a second end of the compound microlens that is parallel to and opposite of the first end of the compound microlens.

34. The display system as recited in claim 13, wherein compound microlens comprises a pyramidal frustrum.

35. The display system as recited in claim 13, wherein compound microlens comprises a conical frustrum.

36. The display system as recited in claim 13, wherein compound microlens comprises a compound frustrum.

38. The display system as recited in claim 13, wherein the active layer is configured to physically move towards the light guide, when the pixel is activated to emit light, in a manner so that at least some of the first set of collector-coupler features contact the light guide.

40. The display system as recited in claim 38, wherein, when the pixel is inactivated to emit light, the active layer is positioned so that the first set of collector-coupler features are not in contact with the light guide.

24. A pixel, comprising:

a light guide;

an active layer; and

collimator features on an external surface of said active layer, wherein said collimator features are configured to interact with light waves that approach a vicinity of an interface between said active layer'"'"'s external surface and said collimator features in order to increase a probability of light waves exiting said external surface of said active layer and entering said collimator features.

25. The display as recited in claim 24, wherein optical properties of said collimator features are selected so as to redirect light waves that would otherwise leave said active layer'"'"'s external surface to leave said collimator features'"'"' external surface more nearly in a direction perpendicular to said external surface.

26. A display system, comprising:

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

a light guide;

an active layer; and

collimator features on an external surface of said active layer, wherein said collimator features are configured to interact with light waves that approach a vicinity of an interface between said active layer'"'"'s external surface and said collimator features in order to increase a probability of light waves exiting said external surface of said active layer and entering said collimator features.