HEAD-MOUNTED PROJECTION DISPLAY USING REFLECTIVE MICRODISPLAYS

• US 20110037951A1
• Filed: 01/21/2009
• Published: 02/17/2011
• Est. Priority Date: 01/22/2008
• Status: Active Grant

• Current Assignee: Arizona Board of Regents (University of Arizona)
• Original Assignee: Arizona Board of Regents (University of Arizona)
• Inventors: Zhang, Rui, Hua, Hong
• Granted Patent: US 8,511,827 B2
• Time in Patent Office: Days
• US Class Current: 353/20
• CPC Class Codes: G02B 13/004 having four lenses
• CPC Class Codes: G02B 13/0065 having a beam-folding prism or mirror
• CPC Class Codes: G02B 13/04 Reversed telephoto objectives
• CPC Class Codes: G02B 13/16 for use in conjunction with image converters or intensifiers , or for use with projectors, e.g. objectives for projection TV
• CPC Class Codes: G02B 13/22 Telecentric objectives or lens systems
• CPC Class Codes: G02B 2027/0118 comprising devices for improving the contrast of the display / brillance control visibility
• CPC Class Codes: G02B 2027/0123 comprising devices increasing the field of view
• CPC Class Codes: G02B 27/0172 characterised by optical features
• CPC Class Codes: G02B 27/286 for controlling or changing the state of polarisation, e.g. transforming one polarisation state into another G02B5/3083 takes precedence; light guide coupling means utilising polarising elements G02B6/34
• CPC Class Codes: G02B 5/30 Polarising elements light-modulating devices with active elements G02F1/00
• CPC Class Codes: G02B 5/3083 Birefringent or phase retarding elements G02B5/3008, G02B5/3016 take precedence; systems for polarisation control G02B27/286; manufacturing phase modulating patterns by lithographic processes G03F7/001
• CPC Class Codes: G02B 9/34 having four components only

Abstract

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.

Claims

1. A compact, telecentric projection lens for use in a head-mounted projection display system, comprising a plurality of lens elements configured to have an overall length that is no more than about two times the effective focal length of the projection lens and configured so that the projection lens is telecentric in image space.

2. The compact, telecentric projection lens according to claim 1, wherein the overall length is no more than about 85% larger than the effective focal length of the projection lens.

3. The compact, telecentric projection lens according to claim 1, wherein the back focal length is about 40% larger than the effective focal length of the projection lens.

4. The compact, telecentric projection lens according to claim 1, wherein the projection lens comprises a diffractive optical element.

5. The compact, telecentric projection lens according to claim 1, wherein the plurality of lens elements includes a final lens element closest to the image plane, the final lens element including a diffractive optical element disposed thereon.

6. The compact, telecentric projection lens according to claim 5, wherein the final lens element includes an aspheric surface.

7. The compact, telecentric projection lens according to claim 6, wherein the diffractive optical element is disposed on the aspheric surface.

8. The compact, telecentric projection lens according to claim 1, wherein at least two-thirds of the optical elements comprise plastic.

9. The compact, telecentric projection lens according to claim 1, wherein the ratio of the weight of the projection lens to the square of the F-number of the projection lens is less than about 2 to 1.

10. The compact, telecentric projection lens 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 of at least two orders of magnitude larger than the effective focal length of the projection lens.

11. A compact, telecentric projection lens, wherein the ratio of the weight of the projection lens to the square of the F-number of the projection lens is less than about 2 to 1.

12. A telecentric optical illumination system for use with a reflective microdisplay, comprising:

a source of optical radiation having a first polarization state;

a polarized beamsplitter disposed at a location to receive optical radiation from the optical radiation source and oriented relative to the source of optical radiation to reflect the received optical radiation;

an optical retarder disposed at a location relative to the beamsplitter to receive optical radiation reflected by the beamsplitter and oriented to convert the polarization state of the received optical radiation to be circularly polarized; and

a reflector having optical power disposed at a location to receive the circularly polarized optical radiation from the optical retarder and to reflect the received optical radiation back through the retarder and beamsplitter,

wherein the pupil of the illumination system is disposed at the source of optical radiation to provide an optical illumination system that is telecentric in image space.

13. The optical illumination system according to claim 12, wherein the reflector is disposed one reflector focal length away from the source of optical radiation.

14. The optical illumination system according to claim 12, wherein the reflector comprises a concave spherical surface.

15. The optical illumination system according to claim 12, wherein the retarder comprises a quarter-wave retarder placed between the reflector and beamsplitter with the fast axis of the retarder oriented at about 45 degrees to the polarization direction of the first polarization state.

16. The optical illumination system according to claim 12, wherein source of optical radiation comprises a LED.

17. The optical illumination system according to claim 12, comprising a tapered light pipe disposed proximate the source of optical radiation.

18. The optical illumination system according to claim 17, wherein the light pipe comprises a plurality of mirrors oriented in the shape of a truncated pyramid.

19. A head-mounted projection display system, comprising:

the optical illumination system according to claim 12;

a microdisplay disposed one reflector focal length away from the reflector for receiving optical radiation from the reflector; and

a projection lens, telecentric in image space, located so that the image plane is disposed proximate the microdisplay.

20. The head-mounted projection display system according to claim 19, comprising:

a polarized projection beamsplitter disposed at about a 45 degree angle relative to the optical axis and disposed at a location to receive optical radiation transmitted by the projection lens;

a projection system quarter-wave retarder disposed at a location to receive optical radiation reflected by the projection beamsplitter; and

a projection screen disposed at a location to receive optical radiation from the projection system quarter-wave retarder.

21. The head-mounted projection display system according to claim 19, wherein the overall length of the projection lens is no more than about 85% larger than the effective focal length of the projection lens.

22. The head-mounted projection display system according to claim 19, wherein the back focal length of the projection lens is about 40% larger than the effective focal length of the projection lens.

23. The head-mounted projection display system according to claim 19, wherein the projection lens comprises a diffractive optical element.

24. The head-mounted projection display system according to claim 19, 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.

25. The head-mounted projection display system according to claim 24, wherein the final lens element includes an aspheric surface.

26. The head-mounted projection display system according to claim 25, wherein the diffractive optical element is disposed on the aspheric surface.

27. The head-mounted projection display system according to claim 19, wherein the projection lens comprises a plurality of optical elements, and at least two-thirds of the optical elements comprise plastic.

28. The head-mounted projection display system according to claim 19, wherein the ratio of the weight of the projection lens to the square of the F-number of the projection lens is less than about 2 to 1.

29. The head-mounted projection display system according to claim 19, 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.

30. The head-mounted projection display system according to claim 19, wherein the projection lens comprises a plurality of lens elements configured to have an overall length that is no more than about two times the effective focal length of the projection lens and configured so that the projection lens is telecentric in image space.