Waveguide combiners having arrangements for image uniformity
Embodiments described herein relate to waveguide combiners having arrangements for image uniformity. The waveguide combiners includes an input coupling grating (ICG) defined by a plurality of input structures, a pupil expansion grating (PEG) defined by a plurality of expansion structures, an output coupling grating (OCG) defined by a plurality of output structures The waveguide combiners includes at least one of a pixelated phase modulator is aligned with the PEG of the first side of the waveguide combiners, at least one of a Y expander and an X expander disposed on a second side of the waveguide combiners opposing the first side, or a pupil shifting mechanism operable to shift incident beams of light between a first position and a second position of the ICG.
1. A waveguide combiner, comprising:
an input coupling grating (ICG) defined by a plurality of input structures;
a pupil expansion grating (PEG) defined by a plurality of expansion structures disposed over a first side of the waveguide combiner;
an output coupling grating (OCG) defined by a plurality of output structures; and
a pixelated phase modulator disposed on a second side of the waveguide combiner opposing the first side of the waveguide combiner, the pixelated phase modulator aligned with the PEG of the first side of the waveguide combiner.
2. The waveguide combiner of claim 1 , wherein the pixelated phase modulator is a liquid crystal spatial light modulator (LC-SLM).
3. The waveguide combiner of claim 1 , wherein the PEG is operable to diffract and out-couple a beam interacting with the PEG as a first T−1 beam and a T−1 second beam with different local intensities and wherein the pixelated phase modulator is configured to tune the first and second T−1 beams from the PEG and out-couple them to the OCG with a uniform intensity for all angles.
4. The waveguide combiner of claim 3 , wherein the pixelated phase modulator is configured to tune a phase difference between the first T−1 beam and the second T−1 beam diffracted and out-coupled by the PEG.
5. The waveguide combiner of claim 1 , wherein the pixelated phase modulator comprises a plurality of pixels in a region where a Mach-Zehnder interference pattern by a beam interacting with the PEG could occur.
6. A waveguide combiner, comprising:
an input coupling grating (ICG) defined by a plurality of input structures disposed over a first side of the waveguide combiner;
a pupil expansion grating (PEG) defined by a plurality of expansion structures, the PEG having at least one of a Y expander and an X expander disposed on a second side of the waveguide combiner opposing the first side; and
an output coupling grating (OCG) defined by a plurality of output structures.
7. The waveguide combiner of claim 6 , wherein the Y expander has a second grating vector that is the same as a first grating vector of the ICG.
8. The waveguide combiner of claim 6 , wherein the X expander has a third grating vector that is orthogonal to a first grating vector of the ICG.
9. The waveguide combiner of claim 6 , wherein the X expander has a third grating vector with a first pitch that is the same as a second pitch of a first grating vector of the ICG.
10. The waveguide combiner of claim 6 , wherein the X expander has a third grating vector that is the same as a fourth grating vector of the OCG.
11. The waveguide combiner of claim 6 , wherein the Y expander and the X expander are on opposite sides of the waveguide combiner.
12. The waveguide combiner of claim 6 , wherein the at least one of the Y expander and the X expander disposed on the second side of the waveguide combiner is operable to provide a uniform out-coupled image from the OCG.
13. The waveguide combiner of claim 6 , wherein the at least one of the Y expander and the X expander disposed on the second side of the waveguide combiner is operable to avoid interference caused by splitting of beams interacting with the PEG.
14. A waveguide combiner, comprising:
an input coupling grating (ICG) defined by a plurality of input structures;
a pupil expansion grating (PEG) defined by a plurality of expansion structures;
an output coupling grating (OCG) defined by a plurality of output structures; and
a pupil shifting mechanism operable to shift incident beams of light between a first position and a second position of the ICG.
15. The waveguide combiner of claim 14 , wherein the pupil shifting mechanism comprises a first liquid crystal (LC) switch, a birefringent slab, and a second LC switch.
16. The waveguide combiner of claim 15 , wherein when no voltage is applied to the first and second LC switches, the pupil shifting mechanism is operable to diffract and displace incident beams of light to be incident of the first position.
17. The waveguide combiner of claim 15 , wherein when a voltage is applied to the first and second LC switches, the pupil shifting mechanism is operable to project incident beams of light through the birefringent slab to be incident of the second position.
18. The waveguide combiner of claim 15 , wherein the birefringent slab comprises an optical axis that is tilted with respect to a surface of the ICG.
19. The waveguide combiner of claim 15 , wherein the first and second LC switches comprise half wave plates with an optic axis that is oriented 45 degrees with respect to a linear polarization of incident beams of light.
20. The waveguide combiner of claim 14 , wherein the pupil shifting mechanism is operable to average intensity patterns of incident beams of light from each of the corresponding first and second positions to a user's eye at the OCG.