Image waveguide with mirror arrays

• US 8,446,675 B1
• Filed: 04/26/2012
• Issued: 05/21/2013
• Est. Priority Date: 04/01/2011
• Status: Active Grant

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Google Inc. (Alphabet Inc.)
• Inventors: Wang, Chia-Jean, Amirparviz, Babak
• Primary Examiner(s): CHOI, WILLIAM C
• Application Number:
  US13/457,151
• Time in Patent Office: 390 Days
• Field of Search: 359/13, 359/629, 359/630, 359/633, 348/115
• US Class Current: 359/633
• CPC Class Codes: G02B 2027/0178 Eyeglass type eyeglass details G02C
• CPC Class Codes: G02B 27/0172 characterised by optical features
• CPC Class Codes: G02B 6/0016 Grooves, prisms, gratings, scattering particles or rough surfaces
• CPC Class Codes: G02B 6/0036 2-D arrangement of prisms, protrusions, indentations or roughened surfaces
• CPC Class Codes: G02B 6/34 utilising prism or grating G02B6/293 takes precedence

Abstract

An image waveguide includes an in-coupling region for receiving input light into the image waveguide and an out-coupling region for emitting output light from the image waveguide. The in-coupling region includes at least one in-coupling structure orientated to direct the input light into the waveguide for propagation towards the out-coupling region as guided light. The out-coupling region includes a two dimensional array of out-coupling mirror structures orientated to reflect the guided light out of the waveguide as the output light.

Claims

1. An optical apparatus, comprising:

a waveguide including first and second surfaces, the waveguide including an in-coupling region for receiving input light into the waveguide and an out-coupling region for emitting output light from the waveguide out the second surface;

at least one in-coupling structure disposed in or on the waveguide at the in-coupling region of the waveguide and orientated to direct the input light for propagation within the waveguide towards the out-coupling region as guided light; and

a two dimensional (“

2D”

) array of out-coupling minor structures disposed in or on the waveguide at the out-coupling region of the waveguide and orientated to reflect the guided light out of the waveguide as the output light.

2. The optical apparatus of claim 1, further comprising a one dimensional (“

1D”

) array of in-coupling mirror structures, including the at least one in-coupling structure, disposed in or on the waveguide at the in-coupling region.

3. The optical apparatus of claim 2,

wherein the 1D and 2D arrays both comprise raised minor structures that are disposed on and rise from the first surface of the waveguide opposite to the second surface of the waveguide through which the input light is incident and the output light is emitted,

wherein the raised mirror structures of the 1D array are laterally offset from each other along the first surface in a first dimension to each reflect a different portion of the input light, and

wherein the raised mirror structures of the 2D array are laterally offset from each other along the first surface in the first dimension and a second dimension.

4. The optical apparatus of claim 3, wherein each of the raised minor structures of at least one of the 1D array or the 2D array comprises:

a first reflective surface orientated obliquely to the second surface; and

a second reflective surface orientated substantially parallel to the second surface.

5. The optical apparatus of claim 4, wherein at least one of the first or second reflective surfaces comprises a metallic layer disposed on the raised mirror structures of the at least one of the 1D or 2D arrays.

6. The optical apparatus of claim 3, further comprising a planarization layer fitted over the 1D and 2D arrays and the first surface of the waveguide, wherein the planarization layer comprises a molded element having a complementary surface that fits to the raised mirror structures of the 1D and 2D arrays.

7. The optical apparatus of claim 2, wherein the in-coupling mirror structures of the 1D array are disposed in columns substantially without interstitial gaps along a plane.

8. The optical apparatus of claim 1, wherein the out-coupling minor structures have a variable spacing between adjacent ones of the out-coupling minor structures along a first axis of the 2D array.

9. The optical apparatus of claim 8, wherein the out-coupling minor structures have a fixed spacing between adjacent ones of the out-coupling minor structures along a second axis of the 2D array.

10. The optical apparatus of claim 8, wherein the out-coupling minor structures have an aperiodic spacing between adjacent ones of the out-coupling minor structures along the first axis of the 2D array.

11. The optical apparatus of claim 1, wherein each of the out-coupling minor structures of the 2D array comprises:

a first reflective surface that is non-optically transmissive and orientated to reflect the guided light as the output light for emission from the out-coupling region; and

a second reflective surface that is non-optically transmissive and orientated to reflect the guided light for propagation further along the out-coupling region of the waveguide prior to emission from the waveguide,

wherein the first reflective surface is orientated to form an oblique angle with the second surface of the waveguide where the output light emerges from the out-coupling region,

wherein the second reflective surface is orientated substantially parallel to the second surface of the waveguide where the output light emerges.

12. The optical apparatus of claim 1, wherein the out-coupling mirror structures of the 2D array comprise metal reflective structures offset from one another with interstitial gaps such that the out-coupling region is partially transparent and permits external light to pass through the out-coupling region in the interstitial gaps between the out-coupling mirror structures.

13. The optical apparatus of claim 1, wherein each of the in-coupling structure has an elongated height along a first axis that is substantially equivalent to an overall height of the 2D array along the first axis.

14. The optical apparatus of claim 1, wherein the waveguide includes an intermediate region disposed between the in-coupling region and the out-coupling region for guiding the guided light between the in-coupling region and the out-coupling region via total internal reflection.

15. The optical apparatus of claim 1, wherein the waveguide further includes:

an intermediate region disposed between the in-coupling region and the out-coupling region for guiding the guided light between the in-coupling region and the out-coupling region; and

at least one metallic reflective layer disposed along a side of the intermediate region, wherein the intermediate region guides the guided light at least partially by reflection off of the metallic reflective layer.

16. The optical apparatus of claim 1, further comprising at least one of a light absorbing surface, an anti-reflective surface, or a light scattering surface disposed on an end region of the waveguide adjacent to the out-coupling region to inhibit the guided light from reflecting back down the waveguide towards the in-coupling region.

17. The optical apparatus of claim 1, wherein the waveguide comprises a single piece injection molded polymer element.

18. A head mounted display, comprising:

a waveguide including;

first and second surfaces;

an in-coupling region for receiving input light into the waveguide and an out-coupling region for emitting output light out of the waveguide;

at least one in-coupling structure disposed at the in-coupling region and orientated to direct the input light towards the out-coupling region as guided light guided along within the waveguide; and

a two dimensional (“

2D”

) array of out-coupling structures disposed at the out-coupling region and orientated to direct the guided light out of the waveguide through the second surface to an eye of the user as the output light;

an image source positioned to launch a computer generated image into the in-coupling region of the waveguide; and

a frame assembly to support the waveguide and the image source for wearing on a head of the user.

19. The head mounted display of claim 18, wherein the waveguide further includes a one dimensional (“

1D”

) array of in-coupling mirror structures, including the at least one in-coupling structure, disposed at the in-coupling region.

20. The head mounted display of claim 19, wherein the 1D and 2D arrays both comprise raised mirror structures that are disposed on and rise from the first surface of the waveguide opposite to the second surface of the waveguide through which the input light is incident and the output light is emitted.

21. The head mounted display of claim 20, wherein each of the raised minor structures of at least one of the 1D array or the 2D array comprises:

a first reflective surface orientated obliquely to the second surface; and

a second reflective surface orientated substantially parallel to the second surface.

22. The head mounted display of claim 18,

wherein the out-coupling structures have a variable spacing between adjacent ones of the out-coupling structures along a first axis of the 2D array, and

wherein the out-coupling structures have a fixed spacing between adjacent ones of the out-coupling structures along a second axis of the 2D array.