Optical combiner with uniform illuminance throughput
An optical device includes a display configured to generate an image light; and a waveguide optically coupled with the display and configured to guide the image light to an exit pupil of the optical device. The waveguide includes an in-coupling element configured to couple the image light into the waveguide, and an out-coupling element configured to decouple the image light out of the waveguide. The out-coupling element includes a grating having a diffraction efficiency gradient along a predetermined direction at a plane of the grating.
1. An optical device, comprising:
a display configured to generate an image light; and
a waveguide optically coupled with the display and configured to guide the image light to an exit pupil of the optical device, the waveguide comprising:
an in-coupling element configured to couple the image light into the waveguide, and
an out-coupling element configured to decouple the image light out of the waveguide,
wherein the out-coupling element includes a grating having a diffraction efficiency gradient along a predetermined direction at a plane of the grating,
wherein the predetermined direction is a pupil-expanding direction,
wherein the grating includes a birefringent material, and
wherein a birefringence of the grating increases along the pupil-expanding direction.
2. The optical device according to claim 1 , wherein the diffraction efficiency increases along the pupil-expanding direction.
3. The optical device according to claim 1 , wherein the grating is a polarization volume hologram (PVH).
4. The optical device according to claim 3 , wherein the PVH includes a polymer with photo-cross-linked cinnamoyl side groups.
5. The optical device according to claim 4 , wherein the PVH includes a liquid crystalline polymer with photo-cross-linked cinnamoyl mesogenic side groups.
6. The optical device according to claim 1 , wherein a thickness of the grating varies along the pupil-expanding direction.
7. The optical device according to claim 6 , wherein the thickness of the grating increases along the pupil-expanding direction.
8. A waveguide, comprising:
an in-coupling element configured to couple a light into the waveguide; and
an out-coupling element configured to decouple the light out of the waveguide,
wherein the out-coupling element includes a grating having a diffraction efficiency gradient along a predetermined direction at a plane of the grating,
wherein the predetermined direction is a pupil-expanding direction,
wherein the grating includes a birefringent material, and
wherein a birefringence of the grating increases along the pupil-expanding direction.
9. The waveguide according to claim 8 , wherein the diffraction efficiency increases along the pupil-expanding direction.
10. The waveguide according to claim 8 , wherein the grating is a polarization volume hologram (PVH).
11. The waveguide according to claim 10 , wherein the PVH includes a polymer with photo-cross-linked cinnamoyl side groups.
12. The waveguide according to claim 11 , wherein the PVH includes a liquid crystalline polymer with photo-cross-linked cinnamoyl mesogenic side groups.
13. The waveguide according to claim 8 , wherein a thickness of the grating varies along the pupil-expanding direction.
14. The waveguide according to claim 13 , wherein the thickness of the grating increases along the pupil-expanding direction.