Eye-imaging apparatus using diffractive optical elements
Examples of eye-imaging apparatus using diffractive optical elements are provided. For example, an optical device comprises a substrate having a proximal surface and a distal surface, a first coupling optical element disposed on one of the proximal and distal surfaces of the substrate, and a second coupling optical element disposed on one of the proximal and distal surfaces of the substrate and offset from the first coupling optical element. The first coupling optical element can be configured to deflect light at an angle to totally internally reflect (TIR) the light between the proximal and distal surfaces and toward the second coupling optical element, and the second coupling optical element can be configured to deflect at an angle out of the substrate. The eye-imaging apparatus can be used in a head-mounted display such as an augmented or virtual reality display.
1. A head mounted display system, comprising:
a transparent eyepiece for projecting images from a light projector system to an eye of a user during operation of the head mounted display, the transparent eyepiece comprising a substrate configured to direct light from the light projector system to the user's eye;
a camera; and
an imaging assembly defining an object plane and an axis normal to the object plane at a central point of an object field of the imaging assembly, the imaging assembly configured to image the user's eye to the camera when the user's eye is positioned in the object field,
the imaging assembly comprising a reflective optical element arranged on an opposite side of the eyepiece from the user's eye, the reflective optical element being arranged to reflect light from the user's eye transmitted by the eyepiece towards the camera, the reflective optical element being positioned away from the axis.
2. The head mounted display system of claim 1 , wherein a surface of the reflective optical element facing the substrate is concave.
3. The head mounted display system of claim 1 , further comprising an optical component with an index of refraction different from an index of refraction of the substrate, wherein the optical component is configured to refract light from the user's eye into the substrate.
4. The head mounted display system of claim 3 , wherein the optical component comprises an optical cover glass or a prescription glass.
5. The head mounted display system of claim 3 , wherein the optical component contacts the substrate.
6. The head mounted display system of claim 1 , wherein an axis of the reflective optical element is nonparallel to the axis of the of the imaging assembly.
7. The head mounted display system of claim 1 , wherein the reflective optical element comprises a prism disposed on a world-side of the substrate.
8. The head mounted display system of claim 7 , wherein the reflective optical element has zero optical power.
9. The head mounted display system of claim 8 , wherein the reflective surface of the reflective optical element is angled at an acute angle relative to the axis.
10. The head mounted display system of claim 7 , further comprising an optical component with an index of refraction different from an index of refraction of the substrate, wherein the optical component is configured to refract light from the user's eye into the substrate.
11. The head mounted display system of claim 10 , wherein the optical component comprises exit pupil expanders.
12. The head mounted display system of claim 10 , wherein the optical component comprises an optical cover glass or a prescription glass.
13. The head mounted display system of claim 1 , wherein the substrate is a transparent waveguide.
14. The head mounted display system of claim 13 , wherein the transparent waveguide comprises a polymer plastic material.
15. The head mounted display system of claim 1 , wherein a surface of the reflective optical element facing the substrate is reflective in the infrared spectrum and transmissive in the visible spectrum.
16. The head mounted display system of claim 1 , further comprising a light source configured to illuminate the user's eye.
17. The head mounted display system of claim 16 , wherein the light source emits infrared light.