Head-mounted projection display using reflective microdisplays
The present invention relates generally to a head-mounted projection display, and more particularly, but not exclusively to a polarized head-mounted projection display including a light engine and a compact, high-performance projection lens for use with reflective microdisplays.
1. An optical illumination system for use with a reflective microdisplay of a headmounted display, comprising:
a microdisplay;
a telecentric projection lens disposed in optical communication with the microdisplay, the microdisplay located at a back focal length of the projection lens; and
a reflector having a reflector focal length associated therewith and disposed one reflector focal length away from the microdisplay.
2. The optical illumination system according to claim 1 , wherein the reflector comprises a concave spherical surface.
3. The head-mounted projection display system according to claim 1 , wherein the overall length of the projection lens is no more than 85% larger than the effective focal length of the projection lens.
4. The head-mounted projection display system according to claim 1 , wherein the back focal length of the projection lens is 40% larger than the effective focal length of the projection lens.
5. The head-mounted projection display system according to claim 1 , wherein the projection lens comprises a diffractive optical element.
6. The head-mounted projection display system according to claim 1 , wherein the projection lens comprises a final lens element disposed closest to the image plane, the final lens element comprising a diffractive optical element disposed thereon.
7. The head-mounted projection display system according to claim 6 , wherein the final lens element includes an aspheric surface.
8. The head-mounted projection display system according to claim 7 , wherein the diffractive optical element is disposed on the aspheric surface.
9. The head-mounted projection display system according to claim 1 , wherein the projection lens comprises a plurality of optical elements, and at least two-thirds of the optical elements comprise plastic.
10. The head-mounted projection display system according to claim 1 , wherein the projection lens comprises a lens group disposed on the object side of the stop of the projection lens, the lens group having an effective focal length two orders of magnitude larger than the effective focal length of the projection lens.
11. The head-mounted projection display system according to claim 1 , wherein the projection lens comprises a plurality of lens elements configured to have an overall length that is no more than two times the effective focal length of the projection lens.