Diffractive optical elements with optical power
A head mounted display system can include a camera, at least one waveguide, at least one coupling optical element that is configured such that light is coupled into said waveguide and guided therein, and at least one out-coupling element. The at least one out-coupling element can be configured to couple light that is guided within said waveguide out of said waveguide and direct said light to said camera. The at least one coupling element may comprise a diffractive optical element having optical power.
1. A head-mounted display system comprising:
an image projector;
a camera; and
an eyepiece configured, during operation of the system, to receive light from the image projector and direct the light along a first optical path to a user's eye, and to direct light reflected from the user's eye along a second optical path to the camera located on a world side of the eyepiece, the eyepiece comprising:
a waveguide having a first surface facing the user's eye;
a first in-coupling optical element on the first surface in the first optical path configured to in-couple light from the image projector into the waveguide;
a second in-coupling optical element on the first surface in the second optical path configured to in-couple light reflected from the user's eye into the waveguide such that the in-coupled light that reflected from the user's eye travels via total internal reflection within the waveguide;
an out-coupling optical element on the first surface in the second optical path configured to out-couple the light reflected from the user's eye and guided within the waveguide out of the waveguide and direct the out-coupled light to the camera;
a light source located on a user side of the eyepiece opposite the camera and arranged to illuminate the user's eye with infrared light, the user side being opposite the world side;
a first lens having optical power disposed on the user side of the eyepiece in the second optical path; and
a second lens having optical power disposed on the world side of the eyepiece.
2. The system of claim 1 , wherein the first lens has positive optical power.
3. The system of claim 1 , wherein the camera comprises a detector array and imaging optics.
4. The system of claim 3 , wherein the imaging optics is configured to image the user's eye onto the detector array.
5. The system of claim 1 , wherein the waveguide comprises a material that is transparent to visible light having a refractive index sufficient for the waveguide to guide light in the waveguide by total internal reflection.
6. The system of claim 1 , further comprising additional waveguides, wherein the waveguide and the additional waveguides form a stack of waveguides.
7. The system of claim 6 , wherein different waveguides of the stack of waveguides are configured to output light with different wavefront divergence corresponding to image points different distances from the user's eye.
8. The system of claim 6 , wherein different waveguides of the stack of waveguides are configured to output light with different colors.
9. The system of claim 6 , wherein different waveguides of the stack of waveguides comprise a first waveguide for red light, a second waveguide for green light, and a third waveguide for blue light.
10. The system of any of claim 1 , wherein the second in-coupling optical element comprises a diffractive optical element.
11. The system of any of claim 1 , wherein the out-coupling optical element comprises a diffractive optical element.
12. The system of claim 1 , wherein the first in-coupling optical element is configured to increase a dimension of an eyebox along at least one axis relative to a dimension of the in-coupled light.
13. The system of claim 12 , further comprising an orthogonal pupil expander comprising at least one light redirecting element in or on the waveguide that is configured to increase a dimension of the eyebox along an axis that is orthogonal to the at least one axis relative to the dimension of the in-coupled light.
14. The system of claim 13 , wherein the at least one light redirecting element comprises a diffractive optical element.
15. The system of claim 1 , wherein the first lens has a first optical power, the second lens has a second optical power, and the first and second optical powers are of a same magnitude and opposite sign.
16. The system of claim 1 , wherein the second lens has positive optical power.
17. The system of claim 1 , wherein at least one of the first and second lenses is a variable focus lens.
18. The system of claim 1 , wherein at least one of the first and second lenses comprises a liquid crystal material.
19. The system of claim 1 , wherein at least one of the first and second lenses comprise a Fresnel lens.