Optical systems with scanning mirror input couplers

1. An electronic device comprising:

a projector configured to produces light;

a waveguide having a lateral surface;

an input coupler configured to couple the light into the waveguide, wherein the waveguide is configured to propagate the light via total internal reflection and wherein the input coupler comprises:

a prism mounted to the lateral surface of the waveguide and having a tilted surface that is oriented at a non-parallel angle with respect to the lateral surface of the waveguide, and

a scanning mirror overlapping the tilted surface of the prism and separated from the tilted surface of the prism by a non-zero distance, wherein the scanning mirror is configured to receive the light through the waveguide and the prism and wherein the scanning mirror is configured to be rotated over a set of orientations while reflecting the light into the waveguide through the prism; and

an output coupler on the waveguide and configured to couple the image light out of the waveguide.

2. The electronic device of claim 1 , wherein the scanning mirror comprises a one-dimensional (1D) scanning mirror.

3. The electronic device of claim 1 , wherein the scanning mirror comprises a two-dimensional (2D) scanning mirror.

4. The electronic device of claim 1 , wherein the scanning mirror comprises a microelectromechanical systems (MEMS) mirror.

5. The electronic device of claim 1 , wherein the scanning mirror comprises a piezoelectric mirror.

6. The electronic device of claim 1 , further comprising an antireflective coating on the tilted surface of the prism.

7. The electronic device of claim 1 , further comprising:

an optical wedge, wherein the waveguide is interposed between the optical wedge and the prism, the optical wedge has a first surface facing the waveguide and a second surface opposite the first surface, the second surface is oriented at a non-parallel angle with respect to the lateral surface of the waveguide, and the optical wedge is configured to transmit the light to the waveguide.

8. The electronic device of claim 1 , wherein the output coupler comprises an optical element selected from the group consisting of: a louvered mirror in the waveguide and a set of volume holograms in the waveguide.

9. The electronic device of claim 1 , further comprising:

one or more processors configured to control the projector to include an image frame in the light and configured to provide the image frame to an eye box by scanning the scanning mirror over each orientation in the set of orientations.

10. The electronic device of claim 1 , further comprising:

sensor circuitry configured to generate gaze tracking data, the scanning mirror being configured to rotate based on a gaze location identified by the gaze tracking data.

11. A method of operating a display system having a projector, one or more processors, a waveguide, an input coupler scanning mirror, and an output coupler on the waveguide, the method comprising:

with the projector, producing image light;

with the input coupler scanning mirror, while in a first orientation, reflecting the light into the waveguide, wherein the display system has an input coupling prism mounted to the waveguide, the waveguide being interposed between the projector and the input coupling prism, wherein the input coupling prism is interposed between the waveguide and the input coupler scanning mirror;

with the output coupler, coupling, out of the waveguide, the light reflected into the waveguide while the input coupler scanning mirror is in the first orientation;

with the input coupler scanning mirror, while in a second orientation different from the first orientation, reflecting the light into the waveguide; and

with the output coupler, coupling, out of the waveguide, the light reflected into the waveguide while the input coupler scanning mirror is in the second orientation.

12. The method of claim 11 , wherein the light includes an image frame, the method further comprising:

with the output coupler, filling a first portion of a field of view of the eye box with the light while the input coupler scanning mirror is in the first orientation, wherein the first portion of the field of view corresponds to a first portion of the image frame; and

with the output coupler, filling a second portion of a field of view of the eye box with the light while the input coupler scanning mirror is in the second orientation, wherein the second portion of the field of view corresponds to a second portion of the image frame that is different from the first portion of the image frame.

13. The method of claim 11 , further comprising sensor circuitry, the method further comprising:

with the sensor circuitry, capturing gaze tracking data; and

with one or more processors, placing the input coupler scanning mirror in the second orientation in response to a change in gaze direction identified by the captured gaze tracking data.

14. The method of claim 13 , further comprising:

with the waveguide, transmitting real world light through the output coupler.

15. The method of claim 11 , wherein the input coupler scanning mirror is configured to perform a two-dimensional rotation to transition from the first orientation to the second orientation.

16. The method of claim 11 , wherein the input coupler scanning mirror is configured to perform a one-dimensional rotation to transition from the first orientation to the second orientation.

17. The method of claim 11 , wherein the input coupler scanning mirror is separated from the input coupling prism by a non-zero distance, and wherein the method further comprises:

with the input coupling prism, transmitting the light produced by the projector to the input coupler scanning mirror; and

with the input coupling prism, transmitting the light reflected by the input coupler scanning mirror into the waveguide.

18. An electronic device comprising:

a projector configured to produce light;

a waveguide having a lateral surface;

an input coupler configured to couple the light into the waveguide, wherein the waveguide is configured to propagate the light coupled into the waveguide by the input coupler via total internal reflection and wherein the input coupler comprises:

a prism mounted to the lateral surface of the waveguide and having a tilted surface that is oriented at a non-parallel angle with respect to the lateral surface of the waveguide, and

a transmissive liquid crystal steering element overlapping the tilted surface of the prism and separated from the tilted surface of the prism by a non-zero distance, wherein the transmissive liquid crystal steering element is configured to transmit the light into the waveguide through the prism while being rotated over a plurality of orientations; and

an output coupler on the waveguide and configured to couple the light out of the waveguide.

19. The electronic device of claim 18 , further comprising:

one or more processors configured to control the projector to include an image frame in the light and configured to provide the image frame to the eye box by scanning the transmissive liquid crystal steering element over each orientation in the plurality of orientations.

20. The electronic device of claim 18 , further comprising:

sensing circuitry configured to gather gaze tracking data associated with the eye box; and

one or more processors is configured to rotate the transmissive liquid crystal steering element based on a gaze location identified by the gathered gaze tracking data.