Liquid crystal color shutters that include reflective polarizers that pass color components of light of a first polarization and that reflect a majority of color components of light of a second polarization

• US 6,204,901 B1
• Filed: 07/07/1998
• Issued: 03/20/2001
• Est. Priority Date: 07/31/1997
• Status: Expired due to Fees

• Current Assignee: Duke University
• Original Assignee: Duke University
• Inventors: Knox, Richard M.
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): CHOWDHURY, TARIFUR RASHID
• Application Number:
  US09/110,652
• Time in Patent Office: 987 Days
• Field of Search: 349/96, 349/117, 349/119, 349/100, 349/97, 349/98, 349/80, 252/299.01, 348/72, 348/751
• US Class Current: 349/96
• CPC Class Codes: G02F 1/133536 Reflective polarizers G02F1/13362 takes precedence
• CPC Class Codes: G02F 1/133545 Dielectric stack polarisers
• CPC Class Codes: G02F 1/13473 for wavelength filtering or for colour display without the use of colour mosaic filters

Abstract

Color shutters that include reflecting linear polarizers can be used in projection display applications. The reflecting linear polarizers are used to reflect the light that would have been absorbed by prior art color shutters. The use of reflecting linear polarizers can resolve overheating and degradation problems of prior art system and projection display systems using sequential color operation can be built and operate reliably.

Claims

1. An apparatus comprising:

a liquid crystal color shutter that sequentially filters different color components of light, the liquid crystal color shutter including a reflecting polarizer that passes first color components of light having a first polarization to provide the first color components to an image surface that is spaced apart from the liquid crystal color shutter and that reflects a majority of second color components of light having a second polarization that is different than the first polarization.

2. The apparatus of claim 1, wherein the reflecting polarizer comprises a reflecting linear polarizer.

3. The apparatus of claim 1, wherein the color shutter further comprises an active retarder that retards the first color components of light in a first operating state and that retards the second components of light in a second operating state.

4. The apparatus of claim 1, wherein the color shutter further comprises a clean-up polarizer.

5. The apparatus of claim 1, wherein the reflecting polarizer comprises an entrance polarizer and the color shutter further comprises an exit reflecting polarizer.

6. The apparatus of claim 5, wherein the exit reflecting polarizer comprises a clean-up polarizer.

7. The apparatus of claim 1, wherein the reflecting polarizer comprises multilayer optical film.

8. The apparatus of claim 1, wherein the color shutter comprises a plurality of reflecting polarizers adapted to retard light passing through the color shutter.

9. The apparatus of claim 1, wherein the reflecting polarizer comprises a substantially nonabsorbing reflecting polarizer.

10. The apparatus of claim 1, wherein the reflecting polarizer passes light through the liquid crystal color shutter to distrubute thermal energy.

11. The apparatus of claim 1, wherein the reflecting polarizer reflects light from the liquid crystal color shutter.

12. The apparatus of claim 1, wherein the color shutter is comprised in a tunable optical filter.

13. The apparatus of claim 1, wherein the color shutter further comprises stages including a reflecting polarizer stage.

14. The apparatus of claim 1, wherein the color shutter further comprises part of a field sequential color display system.

15. A liquid crystal color shutter that sequentially filters different color components of light, comprising:

a reflecting polarizer, positioned in the liquid crystal color shutter, that sequentially passes first color components of light having a first polarization to provide the first color components to an image surface that is spaced apart from the liquid crystal color shutter and that reflects a majority of second color components of light having a second polarization that is different than the first polarization; and

an active retarder, positioned in the liquid crystal color shutter, that retards the first color components of light in a first operating state and retards the second color components of light in a second operating state.

16. The color shutter of claim 15, wherein the color shutter further comprises a passive retarder adapted to impart a fixed retardation on one of light of the polarization and light retarded by the active retarder.

17. The color shutter of claim 16, wherein the passive retarder comprises a birefringent element.

18. The color shutter of claim 15, wherein the reflecting polarizer comprises a reflecting linear polarizer.

19. The color shutter of claim 15, wherein the reflecting polarizer comprises multilayer optical film.

20. The color shutter of claim 15, wherein the active retarder comprises ferroelectric liquid crystals.

21. The color shutter of claim 15, wherein the different operating states of the active retarder comprise discrete operating states.

22. The color shutter of claim 15, wherein the different operating states of the active retarder comprise continuous operating states.

23. The color shutter of claim 15, wherein the reflecting polarizer comprises a nonabsorbing polarizer.

24. The color shutter of claim 15, wherein the reflecting polarizer comprises a substantially nonabsorbing polarizer.

25. The color shutter of claim 15, further comprising a clean-up polarizer adapted to work with the reflecting polarizer.

26. The color shutter of claim 25, wherein the clean-up polarizer comprises an absorptive linear polarizer.

27. The color shutter of claim 15, further comprising stages, wherein each stage is defined by a plurality of reflecting polarizers and each stages comprises a plurality of active retarders.

28. The color shutter of claim 15, wherein the reflecting polarizer and the active retarder comprise part of a field sequential color display system.

29. The projection system of claim 15, wherein the reflecting polarizer comprises multiplayer optical film.