Diffractive optical elements with optical power

1. A head mounted display system configured to project light to an eye of a user to display augmented reality image content in a vision field of said user, said head-mounted display system comprising:

a frame configured to be supported on a head of the user;

an image projector configured to project images into the user's eye to display image content in the vision field of the user;

at least one camera;

at least one waveguide having a user side facing the user;

at least one coupling optical element configured to couple light from the eye of the user into said waveguide, said at least one coupling optical element comprising a diffractive optical element (i) having optical power, (ii) configured to couple light from the eye of the user directly into guided light in said waveguide, and (iii) disposed on the user side of the waveguide; and

at least one out-coupling element configured to couple the guided light in said waveguide out of said waveguide and direct said light to said camera, wherein said guided light propagates from the optical coupling element to the out-coupling element entirely by total internal reflection within said waveguide,

wherein the camera is disposed in an optical path with respect to said at least one out-coupling optical element to receive at least a portion of the light that is coupled into said waveguide via the coupling optical element and guided therein and that is coupled out from said waveguide by said out-coupling coupling element such that images may be captured by said camera.

2. The system of claim 1 , wherein said at least one coupling optical element is configured such that light reflected from the eye of the user wearing the head mounted display system is coupled into said at least one waveguide and guided therein such that images of said eye may be captured by said at least one camera.

3. The system of claim 1 , wherein said at least one coupling optical element is configured such that light reflected from an anterior portion of the eye of the user wearing the head mounted display system is coupled into said waveguide and guided therein such that images of said eye may be captured by said camera such that said at least one camera can capture images of said anterior portion of said eye.

4. The system of claim 1 , wherein said at least one coupling optical element is configured such that light reflected from a corneal surface of said eye of the user wearing the head mounted display system is coupled into said waveguide and guided therein such that images of said eye may be captured by said camera such that said at least one camera can capture images of said corneal surface of said eye.

5. The system of claim 1 , wherein the optical power of said coupling optical element is configured to increase collimation of light reflected from the eye that is coupled into the waveguide to be guided to the camera.

6. The system of claim 1 , wherein the optical power of said coupling optical element is configured to increase collimation of light reflected from an anterior portion of the eye that is coupled into the waveguide to be guided to the camera.

7. The system of claim 1 , wherein the optical power of said coupling optical element is configured to increase collimation of light reflected from the cornea of the eye that is coupled into the waveguide to be guided to the camera.

8. The system of claim 1 , wherein the optical power comprises positive optical power.

9. The system of claim 1 , further comprising an eyepiece disposed on the frame, said eyepiece configured to direct light into said user's eye to display augmented reality image content to the user's vision field, at least a portion of said eyepiece being transparent and disposed at a location in front of the user's eye when the user wears said head-mounted display such that said transparent portion transmits light from an environment in front of the user to the user's eye to provide a view of the environment in front of the user.

10. The system of claim 9 , wherein said eyepiece is configured to receive light from said image projector and to direct said light into said user's eye to display augmented reality image content to the user's vision field.

11. The system of claim 9 , wherein said eyepiece comprises said at least one waveguide.

12. The system of claim 9 , wherein said image projector is configured to direct light into an edge of said eyepiece.

13. The system of claim 1 , further comprising at least one in-coupling optical element configured to in-couple light from said image projector into said at least one waveguide so as to guide light from said image projector for providing said image content to said user's eye.

14. The system of claim 1 , further comprising at least one image content out-coupling optical element configured to couple light from said image projector guided within said waveguide out of said at least one waveguide such that image content can be viewed by the user's eye.

15. The system of claim 14 , wherein said at least one coupling optical element is configured such that light is coupled into a first waveguide and guided therein to said camera, and said at least one image content out-coupling optical element is configured to couple light from said image projector guided within a second waveguide out of said second waveguide.

16. The system of claim 1 , wherein said at least one coupling optical element faces the eye of the user wearing the head mounted imaging system to receive light from said eye.

17. The system of claim 1 , wherein said at least one coupling optical element is configured such that light from the environment in front of the user wearing the head mounted imaging system is coupled into said at least one waveguide and guided therein such that images of said environment may be captured by said camera.

18. The system of claim 1 , wherein said at least one coupling optical element faces the environment in front of the user wearing the head mounted imaging system to receive light from said environment.

19. The system of claim 1 , wherein said at least one coupling optical element is configured such that light is coupled into a first waveguide and guided therein to said camera, and said image projector is configured to couple light into a second waveguide to provide image content to said eye.

20. The system of claim 1 , wherein the head mounted display system is further configured to image light from a world side of the head mounted display to the camera.

21. The system of claim 1 , wherein both the at least one coupling optical element and said out-coupling element are located on the user side of said waveguide.