Efficient collimation of light with optical wedge

• US 7,970,246 B2
• Filed: 09/15/2010
• Issued: 06/28/2011
• Est. Priority Date: 08/21/2009
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Emerton, Neil, Large, Timothy, Travis, Adrian, Bathiche, Steven
• Primary Examiner(s): Healy; Brian M
• Application Number:
  US12/883,077
• Publication Number:
  US 20110044579A1
• Time in Patent Office: 286 Days
• Field of Search: 385/31, 385/36, 385/14, 385/39, 385/42, 385/43, 385/129, 385/130, 385/131, 385/133, 385/146, 385/901, 385/27, 362/623, 362/621, 362/619, 362/611, 362/610, 362/600, 362/516, 362/296.1, 362/215, 362/626, 362/615, 362/97.1, 362/97.2, 359/641, 359/201.2, 345/84
• US Class Current: 385/43
• CPC Class Codes: G02B 27/30 Collimators
• CPC Class Codes: G02B 5/045 Prism arrays
• 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: Y10S 385/901 Illuminating or display apparatus

Abstract

Embodiments of optical collimators are disclosed. For example, one disclosed embodiment comprises an optical waveguide having a first end, a second end opposing the first end, a viewing surface extending at least partially between the first end and the second end, and a back surface opposing the viewing surface. The viewing surface comprises a first critical angle of internal reflection, and the back surface is configured to be reflective at the first critical angle of internal reflection. Further, a collimating end reflector comprising a faceted lens structure having a plurality of facets is disposed at the second end of the optical waveguide.

Claims

1. An optical collimator comprising:

an optical waveguide having

a first end comprising a first light interface;

a second end opposite the first end;

a viewing surface comprising a second light interface extending at least partially between the first end and the second end and having a first critical angle of internal reflection with respect to a normal of the viewing surface;

a back surface opposing the viewing surface, the back surface being configured to be reflective to internally incident light at the first critical angle of internal reflection; and

a collimating end reflector arranged at the second end of the optical waveguide, wherein the collimating end reflector comprises a faceted lens structure.

2. The optical collimator of claim 1, wherein the first end of the optical waveguide is a thin end and the second end of the optical waveguide is a thick end.

3. The optical collimator of claim 1, wherein the collimating end reflector is spherically curved.

4. The optical collimator of claim 1, wherein the faceted lens structure of the collimating end reflector includes a plurality of facets facing the viewing surface and a plurality of facets facing the back surface, each facet facing the viewing surface being positioned adjacent to a facet facing the back surface.

5. The optical collimator of claim 4, wherein each facet facing the viewing surface forms an angle relative to a normal of a surface of the end reflector of three-eighths of a difference between ninety degrees and the first critical angle.

6. The optical collimator of claim 4, wherein each facet facing the back surface forms an angle relative to a normal of a surface of the end reflector equal to three-eighths of a difference between ninety degrees and the first critical angle.

7. The optical collimator of claim 4, wherein each facet facing the viewing surface has a height of less than 500 microns and each facet facing the back surface has a height of less than 500 microns.

8. The optical collimator of claim 1, wherein the back surface includes a second critical angle of internal reflection with respect to a normal of the back surface, wherein the second critical angle of reflection is less than the first critical angle of reflection.

9. The optical collimator of claim 1, wherein the viewing surface of the optical waveguide includes a layer of cladding, and wherein the back surface of the optical waveguide includes a layer of cladding with a different refractive index than the layer of cladding of the viewing surface.

10. The optical collimator of claim 9, wherein the back surface of the optical waveguide includes a cladding and the viewing surface interfaces with air.

11. The optical collimator of claim 1, wherein the back surface of the optical waveguide includes a mirror.

12. The optical collimator of claim 1, wherein the optical waveguide further comprises a first reflective side and a second reflective side, the first reflective side opposite the second reflective side, each reflective side extending from the first end to the second end and from the viewing surface to the back surface.

13. An optical collimator comprising:

an optical wedge comprising

a thin end comprising a first light interface;

a thick end opposite the thin end;

a viewing surface comprising a second light interface extending at least partially between the thin end and the thick end and having a first critical angle of internal reflection with respect to a normal of the viewing surface;

a back surface opposing the viewing surface and having a second critical angle of internal reflection with respect to a normal of the back surface, wherein the second critical angle of reflection is less than the first critical angle of reflection; and

a collimating end reflector arranged at the thick end of the optical wedge, wherein the collimating end reflector comprises a faceted lens structure comprising a plurality of facets arranged at an angle relative to a surface of the thick end, the plurality of facets alternating between facets facing the viewing surface and facets facing the back surface, and the facets having an angle relative to a normal of a surface of the end reflector of three-eighths of a difference between ninety degrees and the first critical angle.

14. The optical collimator of claim 13, wherein the collimating end reflector of the optical wedge is spherically curved.

15. The optical collimator of claim 13, wherein the collimating end reflector of the optical wedge is cylindrically curved.

16. The optical collimator of claim 13, wherein each facet facing the viewing surface has a height of less than 500 microns and each facet facing the back surface has a height of less than 500 microns.

17. The optical collimator of claim 13, wherein the optical wedge further comprises a first reflective side and a second reflective side, the first reflective side opposite the second reflective side, each reflective side extending from the thin end to the thick end and from the viewing surface to the back surface.

18. A method of collimating light via an optical waveguide, the optical waveguide comprising a first end, a second end opposite the first end, a collimating end reflector, a viewing surface extending between the first end and the second end, and a back surface opposing the viewing surface, the method comprising:

injecting light into the first end of the optical waveguide;

delivering the light to the collimating end reflector via total internal reflection;

internally reflecting the light off of the collimating end reflector thereby forming collimated light;

emitting a first portion of collimated light from the viewing surface at a critical angle of reflection;

internally reflecting a second portion of collimated light from the back surface at an angle equal to the critical angle of reflection, and then emitting the second portion of collimated light from the viewing surface after internally reflecting the second portion of collimated light from the back surface.

19. The method of claim 18, wherein reflecting light off of the collimating end reflector comprises reflecting light from a first set of facets and a second set of facets formed in the collimating end reflector, wherein each facet of the first set of facets comprises a normal that points at least partially toward the viewing surface, and wherein each facet of the second set of facets comprises a normal that points at least partially toward the back surface.

20. The method of claim 19, wherein each of the first set of facets has an angle of three-eighths of a difference between ninety degrees and the critical angle of reflection and each of the second set of facets has an angle of three-eighths of the difference between ninety degrees and the critical angle of reflection.