Optical devices including reflective spatial light modulators for projecting augmented reality content

1. An optical device, comprising:

a first waveguide having a first side and an opposing second side;

a projector positioned to project illumination light toward the first side of the first waveguide;

a reflective display positioned to receive the illumination light and to output image light toward the second side of the first waveguide; and

a first in-coupler positioned to:

receive the image light output by the reflective display; and

redirect a first portion of the image light so that the first portion of the image light undergoes total internal reflection inside the first waveguide, wherein:

the projector is positioned to project the illumination light toward the reflective display at least partially through the first in-coupler;

the reflective display has a first optical axis perpendicular to the first waveguide;

the projector has a second optical axis non-perpendicular to the first waveguide so that the illumination light impinges on the first waveguide at an oblique angle, the second optical axis forming an angle with the first optical axis; and

the first in-coupler is an incident angle-selective optical element configured to transmit the illumination light impinging on the first in-coupler at a first incident angle range while redirecting the first portion of the image light impinging on the first in-coupler at a second incident angle range distinct from the first incident angle range.

2. The optical device of claim 1 , wherein the first in-coupler is selected from the group consisting of: a liquid crystal based polarization selective element, a polarization selective element including a metasurface, a polarization selective element including a resonant structured surface, a polarization selective element including a continuous chiral layer, and a polarization selective element including a birefringent material.

3. The optical device of claim 2 , wherein the liquid crystal based polarization selective element is a polarization volume grating.

4. The optical device of claim 2 , wherein the first in-coupler is a transmission grating disposed adjacent the second side of the first waveguide and is configured to redirect the first portion of the image light such that the first portion of the image light is transmitted toward the first side of the first waveguide at an incident angle that is greater than a critical angle associated with the first waveguide.

5. The optical device of claim 2 , wherein the first in-coupler is a reflective polarization volume grating disposed adjacent the first side of the first waveguide and is configured to redirect the first portion of the image light such that the first portion of the image light is deflected toward the second side of the first waveguide at an incident angle that is greater than a critical angle associated with the first waveguide.

6. The optical device of claim 1 , further comprising one or more lenses disposed between the first in-coupler and the reflective display, wherein the one or more lenses is configured to focus the image light from the reflective display.

7. The optical device of claim 1 , wherein:

the reflective display is a spatial light modulator including a reflective surface and a plurality of pixels, a respective pixel in the plurality of pixels having respective modulating elements; and

the respective modulating elements are configured to modulate an amount of the illumination light that reaches the reflective surface so that the image light corresponds to one or more images to be displayed by the optical device.

8. The optical device of claim 1 , wherein:

the first in-coupler is configured to transmit a second portion of the image light, and

the first portion of the image light has a first wavelength range and the second portion of the image light has a second wavelength range distinct from the first wavelength range.

9. The optical device of claim 8 , further including:

a second waveguide disposed between the projector and the first waveguide; and

a second in-coupler configured to:

receive the second portion of the image light transmitted by the first in-coupler; and

redirect a third portion of the image light so that the third portion of the image light undergoes total internal reflection inside the second waveguide, the third portion of the image light including at least a portion of the second portion of the image light.

10. The optical device of claim 1 , wherein the first in-coupler is further positioned to transmit the illumination light projected by the projector toward the reflective display while retaining its polarization.

11. The optical device of claim 1 , wherein:

the projector includes a light source disposed on the second side of the first waveguide and configured to output source light, and

the optical device further includes a reflector configured to reflect the source light toward the first side of the first waveguide as the illumination light.

12. The optical device of claim 11 , wherein the light source has a third optical axis that forms an angle with the first optical axis of the reflective display.

13. The optical device of claim 11 , wherein the reflector has a curved reflective surface configured to focus the source light from the light source such that the illumination light is more collimated than the source light output from the light source.

14. A head-mounted display device, comprising:

the optical device of claim 1 ; and

one or more output couplers positioned at a distance from the first in-coupler, wherein

the one or more output couplers are positioned to receive and redirect the first portion of the image light out of the first waveguide.

15. The head-mounted display device of claim 14 , wherein:

the image light output by the reflective display corresponds to one or more images; and

the first waveguide is further configured to transmit light from one or more objects outside the head-mounted display device such that the one or more images are perceived by a user of the head-mounted display device together with the one or more objects.

16. The head-mounted display device of claim 15 , wherein:

the first in-coupler is configured to transmit a second portion of the image light, and

the first portion of the image light has a first wavelength range and the second portion of the image light has a second wavelength range distinct from the first wavelength range;

the head-mounted display device further comprising:

a second waveguide disposed between the projector and the first waveguide; and

a second in-coupler configured to:

receive the second portion of the image light transmitted by the first in-coupler; and

redirect a third portion of the image light so that the third portion of the image light undergoes total internal reflection inside the second waveguide, the third portion of the image light including at least a portion of the second portion of the image light.

17. The optical device of claim 1 , wherein the projector includes a light source configured to output the illumination light in a first range of directions corresponding to a first divergence and the first waveguide is positioned to receive the illumination light in the first range of directions corresponding to the first divergence.

18. An optical device, comprising:

a first waveguide having a first side and an opposing second side;

a projector positioned to project illumination light toward the first side of the first waveguide;

a reflective display positioned to receive the illumination light and to output image light toward the second side of the first waveguide;

a first in-coupler positioned to:

receive the image light output by the reflective display; and

redirect a first portion of the image light so that the first portion of the image light undergoes total internal reflection inside the first waveguide, wherein:

the projector is positioned to project the illumination light toward the reflective display at least partially through the first in-coupler;

the first in-coupler is further positioned to transmit the illumination light projected by the projector toward the reflective display while retaining its polarization; and

the reflective display has a first optical axis and the projector has a second optical axis that forms an angle with the first optical axis; and

a transmissive optical element disposed between the first waveguide and the reflective display, wherein the projector is configured to project the illumination light having a first polarization toward the transmissive optical element such that the illumination light impinges on the transmissive optical element with incident angles in a first incident angle range, and wherein the transmissive optical element is configured to:

redirect the illumination light toward the reflective display while converting its polarization from the first polarization to a second polarization distinct from the first polarization,

receive, from the reflective display, the image light with incident angles in a second incident angle range distinct from the first incident angle range, the image light having the first polarization, and

transmit the image light received from the reflective display while retaining its polarization.

19. A method comprising:

projecting, by a projector, illumination light toward a first side of a first waveguide;

receiving the illumination light at a reflective display facing a second side of the first waveguide, wherein:

the illumination light received by the reflective display is at least partially projected through a first in-coupler;

the reflective display has a first optical axis perpendicular to the first waveguide; and

the projector has a second optical axis non-perpendicular to the first waveguide so that the illumination light impinges on the first waveguide at an oblique angle, the second optical axis forming an angle with the first optical axis;

in response to receiving the illumination light, outputting image light from the reflective display toward a second side of the first waveguide;

receiving, by the first in-coupler, the image light output by the reflective display;

redirecting, by the first in-coupler, at least a first portion of the image light so that the at least a first portion of the image light undergoes total internal reflection inside the first waveguide; and

transmitting, with the first in-coupler that is an incident angle-selective optical element, the illumination light impinging on the first in-coupler at a first incident angle range while redirecting the first portion of the image light impinging on the first in-coupler at a second incident angle range distinct from the first incident angle range.