Wedge combiner for eye-tracking

1. An optical system comprising:

a first optical element having at least a first optical surface, a second optical surface, and a third optical surface, wherein the first optical surface, the second optical surface, and the third optical surface are non-parallel to one another; and

a plurality of optical elements positioned adjacent to the second optical surface of the first optical element, wherein:

a respective optical element of the plurality of optical elements is configured for at least one of the following:

receiving light transmitted through the first optical surface at a first angle with respect to the second optical surface and directing the light back to the first optical surface at a second angle, that is distinct from the first angle, with respect to the second optical surface; or

receiving light guided through the first optical element at a third angle with respect to the second optical surface and directing the light to the first optical surface at a fourth angle, that is distinct from the third angle, with respect to the second optical surface.

2. The optical system of claim 1 , wherein the respective optical element of the plurality of optical elements is selected from a group consisting of a reflector or a diffraction element.

3. The optical system of claim 1 , wherein light guided through the first optical element is from a light source and enters the first optical element through a third optical surface of the first optical element, the light directed to the first optical surface at the fourth angle with respect to the second optical surface exits the first optical element through the first optical surface of the first optical element to illuminate an object.

4. The optical system of claim 3 , wherein a first portion of the light exits the first optical element at a first location on the second optical surface to a respective optical element of the plurality of optical elements, and a second portion of the light exits the first optical element at a second location on the second optical surface, the first location on the second optical surface being spatially separated from the second location on the second optical surface.

5. The optical system of claim 3 , wherein light received at the third optical surface is separated into a plurality of portions and respective portions of the plurality of portions are transmitted through the first optical surface of the first optical element at discrete locations to illuminate one or more portions of the object.

6. The optical system of claim 3 , wherein object light from the object enters the first optical element through the first optical surface and exits the first optical element through the third optical surface to form an image on an image plane.

7. The optical system of claim 6 , wherein the object light from the object is light derived from the light source.

8. The optical system of claim 3 , wherein the second optical surface is orthogonal to the third optical surface, and the third optical surface intersects the first optical surface at a first acute angle.

9. The optical system of claim 8 , wherein the first optical surface intersects the second optical surface at a second acute angle.

10. The optical system of claim 1 , wherein the first optical element has a shape of a wedge and the third optical surface has a surface area that is smaller than both a surface area of the first optical surface and a surface area of the second optical surface.

11. The optical system of claim 1 , wherein the light transmitted through the first optical surface at the first angle with respect to the second optical surface comprises object light from an object and the object light, after being directed back to the first optical surface at the second angle, with respect to the second optical surface, by the respective optical element of the plurality of optical elements, exits through a third optical surface of the first optical element to form an image of the object on an image plane.

12. The optical system of claim 1 , wherein the first optical element further comprises a first reflective element disposed on the first optical surface.

13. The optical system of claim 12 , wherein the first optical surface comprises regions that are not covered by any reflective element.

14. The optical system of claim 1 , further comprising a second optical element, the second optical element having i) a first optical surface that is parallel to the first optical surface of the first optical element, and ii) a second optical surface that is parallel to the second optical surface of the first optical element, wherein the first optical surface of the second optical element is adjacent to the first optical surface of the first optical element and the second optical element is separated from the first optical element.

15. The optical system of claim 1 , wherein the respective optical element of the plurality of optical elements directs light having a first wavelength and transmits light having a second wavelength, the first wavelength being longer than 750 nm, and the second wavelength being shorter than 750 nm.

16. The optical system of claim 15 , further comprising:

a substrate located adjacent to the second optical surface of the first optical element, wherein:

the plurality of optical elements is coupled with the substrate; and

the respective optical element of the plurality of optical elements has a curved reflective surface.

17. The optical system of claim 15 , further comprising:

a substrate located adjacent to the second optical surface of the first optical element, wherein:

the plurality of optical elements is coupled with the substrate; and

the respective optical element of the plurality of optical elements has a flat reflective surface.

18. The optical system of claim 1 , wherein at least one of the following is satisfied:

the directing the light back to the first optical surface at the second angle includes directing back light of a first wavelength longer than 750 nm while transmitting light of a second wavelength shorter than 750 nm with a transmittance greater than 90%; or

the directing the light back to the first optical surface at the fourth angle includes directing back light of the first wavelength longer than 750 nm while transmitting light of the second wavelength shorter than 750 nm with a transmittance greater than 90%.

19. The optical system of claim 1 , wherein at least one of the plurality of optical elements has a flat surface that is positioned parallel to the second optical surface of the first optical element.

20. An optical system, comprising:

a first optical element having at least a first optical surface, a second optical surface, and a third optical surface, wherein the first optical surface, the second optical surface, and the third optical surface are non-parallel to one another; and

a plurality of optical elements positioned adjacent to the second optical surface of the first optical element, wherein:

a respective optical element of the plurality of optical elements is configured for at least one of the following:

receiving light transmitted through the first optical surface at a first angle with respect to the second optical surface and directing the light back toward the first optical surface at a second angle, that is distinct from the first angle, with respect to the second optical surface; or

receiving light guided through the first optical element at a third angle with respect to the second optical surface and directing the light toward the first optical surface at a fourth angle, that is distinct from the third angle, with respect to the second optical surface; and

the respective optical element has a spatially varying refractive index profile.