Waveguide-Based Displays With Exit Pupil Expander

• US 20170299860A1
• Filed: 04/13/2016
• Published: 10/19/2017
• Est. Priority Date: 04/13/2016
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Inventors: Wall, Richard Andrew, Vallius, Tuomas, Juhola, Mikko
• Granted Patent: US 10,025,093 B2
• Time in Patent Office: Days
• CPC Class Codes: G02B 2027/0118 comprising devices for improving the contrast of the display / brillance control visibility
• CPC Class Codes: G02B 2027/0123 comprising devices increasing the field of view
• CPC Class Codes: G02B 2027/0125 Field-of-view increase by wavefront division
• CPC Class Codes: G02B 2027/0174 holographic
• CPC Class Codes: G02B 26/101 with both horizontal and vertical deflecting means, e.g. raster or XY scanners colour television using laser beams scanning a display screen H04N9/3129
• CPC Class Codes: G02B 27/0081 with means for altering, e.g. enlarging, the entrance or exit pupil
• CPC Class Codes: G02B 27/0172 characterised by optical features
• CPC Class Codes: G02B 3/0062 Stacked lens arrays, i.e. refractive surfaces arranged in at least two planes, without structurally separate optical elements in-between
• CPC Class Codes: G02B 3/04 with continuous faces that are rotationally symmetrical but deviate from a true sphere , e.g. so called "aspheric" lenses
• CPC Class Codes: G02B 6/0026 Wavelength selective element, sheet or layer, e.g. filter or grating
• CPC Class Codes: G02B 6/003 Lens or lenticular sheet or layer

Abstract

A near eye or heads up display system includes a scan beam projector engine, an optical waveguide, and an exit pupil expander (EPE) optically coupled between the scan beam projector engine and the optical waveguide. The EPE improves the optical performance of the display system. The EPE could include a diffusive optical element, diffractive optical element, micro-lens array (MLA), or relay of aspherical lenses. A dual MLA EPE may have cells that prevent cross-talk between adjacent pixels. A dual MLA EPE may have a non-periodic lens array. The optical power of one MLA may be different from the other MLA.

Claims

1. An apparatus, comprising:

a scan beam projector configured to project a light beam;

an optical waveguide including a bulk-substrate, an input-coupler an output-coupler, and a diffractive optical element between the input-coupler and the output-coupler; and

an exit pupil expander optically coupled between the scan beam projector and the optical waveguide, the exit pupil expander configured to couple the light beam from the scan beam projector into the input-coupler.

2. The apparatus of claim 1, wherein the exit pupil expander comprises a diffuser configured to expand an exit pupil associated with the scan beam projector.

3. The apparatus of claim 1, wherein the exit pupil expander comprises a diffractive optical element configured to expand an exit pupil associated with the scan beam projector.

4. The apparatus of claim 1, wherein the exit pupil expander comprises a dual microlens array configured to expand an exit pupil associated with the scan beam projector.

5. The apparatus of claim 4, wherein the dual microlens array comprises a first microlens array that is configured to receive the light beam in first lenses in a first plane and a second microlens array that is configured to output the light beam in second lenses in a second plane parallel to the first plane, wherein ones of the second lenses correspond to ones of the first lenses but are shifted relative to the first lenses in a direction parallel to the second plane.

6. The apparatus of claim 4, wherein the dual microlens array comprises a first microlens array that is configured to receive the light beam in first lenses in a first plane and a second microlens array that is configured to output the light beam in second lenses in a second plane parallel to the first plane, wherein the first lenses are periodic and the second lenses are non-periodic.

7. The apparatus of claim 4, wherein the dual microlens array comprises a first microlens array that is configured to receive the light beam and a second microlens array that is configured to output the light beam, wherein the second microlens array has a different optical power than the first microlens array.

8. The apparatus of claim 1, wherein the exit pupil expander comprises a series of aspherical refractive optical elements configured to expand an exit pupil of the scan beam projector.

9. The apparatus of claim 1, further comprising a series of refractive optical elements comprising a first set of lenses and a second set of lenses, wherein the exit pupil expander is optically coupled between the first and second sets of lenses, wherein the series of refractive optical elements correct for chromatic aberration.

10. The apparatus of claim 1, wherein the input-coupler comprises a diffractive optical element configured to diffract the light beam to the diffractive optical element, wherein the diffractive optical element is configured to diffract the light beam to the output-coupler, wherein the diffractive optical element is configured to expand a pupil of the light beam in at least one direction.

11. The apparatus of claim 1, further comprising an opacity filter aligned with the optical waveguide, the opacity filter is configured to selectively block natural light from passing through the optical waveguide.

12. A method comprising:

scanning a light beam using a scan beam projector;

expanding an exit pupil of the light beam from the scan beam projector using an exit pupil expander;

optically coupling the light beam from the exit pupil expander into an input-coupler of an optical waveguide;

diffracting the light beam from the input-coupler to an intermediate diffractive element in the optical waveguide;

diffracting the light beam from the intermediate diffractive element to an output-coupler in the optical waveguide; and

diffracting the light beam from the output-coupler to outside of the optical waveguide.

13. The method of claim 12, wherein expanding the exit pupil of the light beam from the scan beam projector using the exit pupil expander comprises:

channeling portions of the light beam that correspond to virtual pixels in the light beam through different physical sections of the exit pupil expander while preventing cross talk between adjacent virtual pixels.

14. The method of claim 12, wherein the exit pupil expander comprises a microlens array, wherein expanding the exit pupil of the light beam from the scan beam projector using the exit pupil expander comprises:

refracting the light beam from lenses in the microlens array at different angles depending on a spatial location of the lenses in the microlens array.

15. The method of claim 12, wherein expanding the exit pupil of the light beam from the scan beam projector using the exit pupil expander comprises:

applying a first optical power to the light beam at an input of the exit pupil expander; and

applying a second optical power to the light beam at an output of the exit pupil expander, the second optical power is not equal to the first optical power.

16. A see-through, near eye display system, comprising:

a light engine comprising a laser, a scanning mirror, and logic configured to scan a light beam from the laser with the scanning mirror;

a pupil replicator including a bulk-substrate, an input-coupler an output-coupler, and a diffractive optical element between the input-coupler and the output-coupler, the output-coupler configured to deliver the light beam to an eye of a wearer of the see-through, near eye display system; and

an exit pupil expander optically coupled between the light engine and the pupil replicator, the exit pupil expander configured to couple the light beam from the light engine into the input-coupler.

17. The see-through, near eye display system of claim 16, wherein the exit pupil expander comprises a dual microlens array configured to provide a spatially dependent refraction angle.

18. The see-through, near eye display system of claim 16, wherein the exit pupil expander comprises a dual microlens array having a first microlens array configured to receive the light beam in first lenses in a first plane and a second microlens array configured to output the light beam in second lenses in a second plane parallel to the first plane, wherein ones of the second lenses have a different numerical aperture from ones of the first lenses.

19. The see-through, near eye display system of claim 16, wherein the exit pupil expander comprises a dual microlens array having a body having a first side and a second side, a first microlens array having first lenses disposed on the first side, and a second microlens array having second lenses disposed on the second side, the body comprising cells configured to channel light from ones of the first lenses to corresponding ones of the second lenses, the cells configured to prevent cross-talk between adjacent cells.

20. The see-through, near eye display system of claim 16, wherein the exit pupil expander comprises a relay of aspherical lenses that expand an exit pupil of the light engine.