Immersed hot mirrors for illumination in eye tracking

1. An illuminator for eye tracking comprising:

a light source;

a substrate configured to be placed in front of an eye of a user, the substrate comprising a first surface facing the eye; and

a plurality of reflectors fixed within the substrate,

wherein:

the light source is configured to emit light in a first wavelength range to impinge on the first surface from outside of the substrate, thereby illuminating each reflector of the plurality of reflectors;

each reflector of the plurality of reflectors is configured to reflect the impinging light in the first wavelength range to the eye of the user such that each reflector of the plurality of reflectors forms a corresponding image of the light source, wherein different images of the light source formed by different reflectors of the plurality of reflectors are disposed at different locations in front of the eye, and to transmit light in a second wavelength range different from the first wavelength range;

the substrate is transparent to both the light in the first wavelength range and the light in the second wavelength range; and

each reflector of the plurality of reflectors is different in size and surface curvature from other reflectors of the plurality of reflectors.

2. The illuminator of claim 1 , wherein:

the first wavelength range is a near infrared range;

the second wavelength range is a visible range for a human eye; and

the plurality of reflectors comprises at least one hot mirror, the at least one hot mirror configured to reflect light in the near infrared range and transmit light in the visible range.

3. The illuminator of claim 1 , wherein:

each reflector of the plurality of reflectors comprises a reflecting surface; and

the light source is configured to directly illuminate the reflecting surface of each reflector from outside of the substrate.

4. The illuminator of claim 3 , wherein the reflecting surface comprises a flat surface, a concave surface, a convex surface, a cylindrical surface, an aspherical surface, or a freeform surface.

5. The illuminator of claim 3 , wherein the plurality of reflectors comprises a plurality of dielectric layers, a diffractive optical element, or a reflective material layer at the reflecting surface.

6. The illuminator of claim 1 , wherein each reflector of the plurality of reflectors is configured to reflect the light in the first wavelength range from the light source to a different area of the eye.

7. The illuminator of claim 2 , wherein:

each reflector of the plurality of reflectors comprises a reflecting surface; and

the reflecting surface of each reflector of the plurality of reflectors is configured such that a virtual image of the light source formed by the reflecting surface of each reflector of the plurality of reflectors is at a different location in front of the eye of the user.

8. The illuminator of claim 1 , wherein the substrate comprises a curved surface.

9. The illuminator of claim 1 , wherein the substrate comprises at least one of a glass, quartz, plastic, polymer, ceramic, or crystal.

10. The illuminator of claim 1 , wherein the light source comprises a laser, a light-emitting diode, or a lamp.

11. An eye-tracking unit for a near-eye display device, the eye-tracking unit comprising:

a light source;

a camera;

a substrate configured to be placed in front of an eye of a user; and

a plurality of reflectors fixed within the substrate,

wherein:

the light source is configured to emit light in a first wavelength range to impinge on the first surface from outside of the substrate, thereby illuminating each reflector of the plurality of reflectors;

each reflector of the plurality of reflectors is configured to reflect the impinging light in the first wavelength range to the eye of the user such that each reflector of the plurality of reflectors forms a corresponding image of the light source, wherein different images of the light source formed by different reflectors of the plurality of reflectors are disposed at different locations in front of the eye, and to transmit light in a second wavelength range from a display panel of the near-eye display device to the eye of the user;

the camera is configured to receive light in the first wavelength range and reflected by the eye of the user;

the substrate is transparent to both the light in the first wavelength range and the light in the second wavelength range; and

each reflector of the plurality of reflectors is different in size and surface curvature from other reflectors of the plurality of reflectors.

12. The eye-tracking unit of claim 11 , wherein the light source and the camera are coupled to or embedded in a body of the near-eye display device.

13. The eye-tracking unit of claim 11 , wherein the substrate is a part of the display panel of the near-eye display device.

14. The eye-tracking unit of claim 11 , wherein:

the light source is configured to directly illuminate the plurality of reflectors with the light in the first wavelength range from outside of the substrate; and

each reflector of the plurality of reflectors is configured to reflect the light in the first wavelength range from the light source to a different area of the eye.

15. The eye-tracking unit of claim 11 , further comprising an imaging reflector located within the substrate, the imaging reflector configured to:

receive light in the first wavelength range reflected by the eye of the user;

reflect the light in the first wavelength range reflected by the eye of the user to the camera; and

transmit the light in the second wavelength range from the display panel of the near-eye display device to the eye of the user.

16. A method of tracking an eye of a user of a near-eye display, the method comprising:

illuminating, by light in a first wavelength range emitted by a light source, a plurality of reflectors fixed within a substrate in front of the eye of the user, wherein the light in the first wavelength range illuminates a first surface of the substrate facing the eye from outside of the substrate, thereby illuminating each reflector of the plurality of reflectors comprising a first reflector;

reflecting, by each reflector of the plurality of reflectors, the light in the first wavelength range towards the eye of the user at a different angle for each reflector, such that each reflector of the plurality of reflectors forms a corresponding image of the light source, wherein different images of the light source formed by different reflectors of the plurality of reflectors are disposed at different locations in front of the eye; and

transmitting light in a second wavelength range from a display panel of the near-eye display through the substrate and the plurality of reflectors and to the eye of the user;

wherein each reflector of the plurality of reflectors is different in size and surface curvature from other reflectors of the plurality of reflectors.

17. The method of claim 16 , further comprising:

receiving, by a camera, light in the first wavelength range reflected by the eye of the user; and

generating, by the camera using the received light in the first wavelength range reflected by the eye of the user, an image frame comprising a plurality of images of the light source reflected by the eye of the user, each image corresponding to a different reflector of the plurality of reflectors.

18. The method of claim 16 , further comprising:

receiving, by a second reflector within the substrate, light in the first wavelength range reflected by the eye of the user;

reflecting, by the second reflector, the received light in the first wavelength range reflected by the eye of the user, to a camera; and

transmitting the light in the second wavelength range from the display panel of the near-eye display through the substrate and the second reflector and to the eye of the user.

19. The method of claim 16 , further comprising:

directly illuminating, by the light in the first wavelength range emitted from the light source, a third reflector of the plurality of reflectors within the substrate, wherein the first reflector reflects light to a first area of the eye of the user;

reflecting, by the third reflector, the light in the first wavelength range to a second, different area of the eye of the user; and

transmitting the light in the second wavelength range from the display panel of the near-eye display through the substrate and the third reflector to the eye of the user.