Optical waveguide beam splitter for directional illumination of display

1. An optical device, comprising:

a light source configured to provide illumination light;

a waveguide having:

an input surface;

an output surface distinct from and non-parallel to the input surface; and

an output coupler, wherein:

the waveguide is configured to:

receive, at the input surface, the illumination light provided by the light source;

propagate the illumination light via total internal reflection; and

redirect, by the output coupler, the illumination light so that the illumination light is output from the output surface for illuminating a spatial light modulator; and

the output coupler is configured to:

receive the illumination light at a first location on the output coupler;

redirect from the first location on the output coupler a first portion of the illumination light in a first direction and redirect from the first location on the output coupler a second portion of the illumination light that is mutually exclusive to the first portion of the illumination light in a second direction that is distinct from the first direction;

receive the second portion of the illumination light at a second location on the output coupler distinct and separate from the first location on the output coupler; and

redirect from the second location on the output coupler a third portion of the illumination light that is a subset of the second portion of the illumination light in the first direction and redirect from the second location on the output coupler a fourth portion of the illumination light that is a subset of the second portion of the illumination light and mutually exclusive to the third portion of the illumination light in the second direction;

a reflective polarizer disposed on a first side of the waveguide and configured to transmit light having a first polarization and reflect light having a second polarization different from the first polarization;

a flat reflector disposed on a second side of the waveguide, that is opposite to the first side of the waveguide, to receive the light reflected by the reflective polarizer and reflect the received light toward the reflective polarizer; and

an optical retarder disposed between the reflective polarizer and the flat reflector.

2. The optical device of claim 1 , further comprising:

the spatial light modulator positioned to:

receive the illumination light output from the output surface of the waveguide;

modulate an amplitude or phase of at least a portion of the illumination light; and

output modulated light.

3. The optical device of claim 1 , wherein the output coupler is disposed adjacent to the output surface.

4. The optical device of claim 3 , wherein:

the output coupler includes a turning film configured to redirect the illumination light propagating in the waveguide so that at least a portion of the illumination light is output from the output surface of the waveguide in a first direction.

5. The optical device of claim 4 , wherein:

the turning film has a first refractive index and the waveguide has a second refractive index that is substantially same as the first refractive index.

6. The optical device of claim 4 , wherein:

the first direction is non-parallel and non-perpendicular with a reference plane defined by the waveguide.

7. The optical device of claim 1 , wherein:

the output coupler is a holographic film that is configured to redirect light in a direction based on an angle of incidence of the light upon the holographic film; and

the illumination light is incident upon the holographic film at a first range of incident angles.

8. The optical device of claim 1 , further comprising:

a tapered waveguide positioned between the waveguide and the light source, the tapered waveguide configured to receive the illumination light provided by the light source and steer the illumination light into the waveguide.

9. The optical device of claim 1 , wherein:

the output coupler includes a plurality of optical elements;

the plurality of optical elements is coupled to the output surface of the waveguide; and

the plurality of optical elements is configured to redirect the illumination light so that the illumination light is output from the output surface of the waveguide.

10. The optical device of claim 1 , wherein:

the waveguide includes an optical surface opposite to the output surface and distinct from the input surface and the output surface;

the output coupler includes a plurality of optical elements;

the plurality of optical elements is coupled to the optical surface of the waveguide; and

the plurality of optical elements is configured to redirect the illumination light so that the illumination light is output from the output surface of the waveguide.

11. The optical device of claim 1 , wherein the optical retarder is disposed on the second side of the waveguide.

12. A method of providing illumination light, the method comprising:

providing, from a light source, illumination light;

receiving, at an input surface of a waveguide, the illumination light provided by the light source, wherein the waveguide further includes:

an output surface that is distinct from and non-parallel to the input surface; and

an output coupler;

propagating, in the waveguide, the illumination light via total internal reflection;

redirecting, by the output coupler, the illumination light so that the illumination light is output from the output surface of the waveguide for illuminating a spatial light modulator including:

receiving the illumination light at a first location on the output coupler;

redirecting from the first location on the output coupler a first portion of the illumination light in a first direction and redirecting from the first location on the output coupler a second portion of the illumination light that is mutually exclusive to the first portion of the illumination light in a second direction that is distinct from the first direction;

receiving the second portion of the illumination light at a second location on the output coupler distinct and separate from the first location on the output coupler; and

redirecting from the second location on the output coupler a third portion of the illumination light that is a subset of the second portion of the illumination light in the first direction and redirecting from the second location on the output coupler a fourth portion of the illumination light that is a subset of the second portion of the illumination light and mutually exclusive to the third portion of the illumination light in the second direction;

transmitting, through a reflective polarizer disposed on a first side of the waveguide, light having a first polarization and reflecting, with the reflective polarizer, light having a second polarization different from the first polarization; and

receiving, with a flat reflector disposed on a second side of the waveguide, that is opposite to the first side of the waveguide, the light reflected by the reflective polarizer and reflecting the received light toward the reflective polarizer, wherein an optical retarder is disposed between the reflective polarizer and the flat reflector.

13. The method of claim 12 , further comprising:

receiving, at the spatial light modulator, the illumination light output from the output surface of the waveguide;

modulating, at the spatial light modulator, an amplitude or phase of at least a portion of the illumination light; and

outputting modulated light from the spatial light modulator.

14. The method of claim 12 , wherein:

the output coupler is disposed adjacent to the output surface of the waveguide.

15. The method of claim 14 , wherein:

the output coupler is a turning film and the method further comprises:

redirecting, by the turning film, the illumination light propagating in the waveguide so that at least a portion of the illumination light is output from the output surface of the waveguide in a first direction.

16. The method of claim 12 , wherein:

the output coupler is a holographic film;

the illumination light is incident upon the holographic film at a first range of incident angles; and

the method further comprises:

redirecting, by the holographic film, the illumination light in a first direction based on the first range of incident angles.

17. The method of claim 12 , further comprising:

receiving, by a tapered waveguide positioned between the waveguide and the light source, the illumination light provided by the light source; and

steering the illumination light into the waveguide.

18. The method of claim 12 , wherein:

the output coupler includes a plurality of optical elements, the plurality of optical elements coupled to the output surface of the waveguide, and the method further includes:

redirecting, by the plurality of optical elements, the illumination light so that the illumination light is output from the output surface of the waveguide.

19. The method of claim 12 , wherein:

the output coupler includes a plurality of optical elements, the plurality of optical elements coupled to an optical surface opposite to, and distinct from, the output surface of the waveguide, and the method further comprises:

redirecting, by the plurality of optical elements, the illumination light so that the illumination light is output from the output surface of the waveguide.