Polarization arrangement

• US 6,764,181 B2
• Filed: 05/16/2002
• Issued: 07/20/2004
• Est. Priority Date: 05/18/2001
• Status: Active Grant

• Current Assignee: Regents of The University of Minnesota (University of Minnesota)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Rudolph, John D., Magarill, Simon
• Primary Examiner(s): Adams, Russell
• Assistant Examiner(s): Cruz, Magda
• Application Number:
  US10/147,274
• Publication Number:
  US 20030058408A1
• Time in Patent Office: 796 Days
• Field of Search: 359/486, 359/489, 359/495, 359/483, 359/583, 353/20, 385/47
• US Class Current: 353/20
• CPC Class Codes: G02B 27/283 used for beam splitting or combining
• CPC Class Codes: G02B 5/3033 in the form of a thin sheet or foil, e.g. Polaroid
• CPC Class Codes: G02B 5/3058 comprising electrically conductive elements, e.g. wire grids, conductive particles
• 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: G02F 1/133528 Polarisers
• CPC Class Codes: H04N 5/7441 the modulator being an array of liquid crystal cells

Abstract

A tilted polarization splitter (13) for use with a projection lens (15) and a light modulating panel (11) is provided. The polarization splitter has an ultra thin substrate (14) whose thickness is chosen so that the depth of focus of the projection lens in imager space is greater than the astigmatism produced by the splitter at its tilted angle. The polarization splitter can be a wire grid polarizer, polarization coating, or birefringence film carried by or formed on the ultra thin, plane parallel plate substrate.

Claims

1. An optical system comprising:

(a) a light modulating panel comprising a plurality of pixels, said pixels having a pixel size which defines an acceptable blur at the panel;

(b) a projection lens for forming an image of the light modulating panel, said projection lens and said acceptable blur defining a depth of focus D in imager space; and

(c) a tilted polarization splitter located between the light modulating panel and the projection lens;

wherein the overall structure of said polarization splitter is suitable for mounting the splitter in the optical system and wherein the splitter comprises a substrate having a thickness T such that the astigmatism introduced by the splitter when mounted at its tilted angle using said overall structure is less than or equal to D.

2. The optical system of claim 1 wherein D is approximately 0.05 millimeters.

3. The optical system of claim 1 wherein T is approximately 0.15 millimeters.

4. The optical system of claim 1 wherein the polarization splitter is tilted at an angle of approximately 45°

.

5. The optical system of claim 1 wherein the polarization splitter is a wire grid polarizer.

6. The optical system of claim 1 wherein the polarization splitter comprises a polarization coating.

7. The optical system of claim 1 wherein the polarization splitter comprises a polarizing birefringence film.

8. The optical system of claim 1 wherein the light modulating panel is a reflective liquid crystal display.

9. The optical system of claim 1 wherein the light modulating panel is a liquid crystal on silicon panel.

10. An optical system comprising:

(a) an illumination system;

(b) a light modulating panel comprising a plurality of pixels, said pixels having a pixel size which defines an acceptable blur at the panel;

(c) a projection lens for forming an image of the light modulating panel, said projection lens and said acceptable blur defining a depth of focus D in imager space; and

(d) a tilted polarization splitter located between the illumination system and the light modulating panel and between the light modulating panel and the projection lens;

wherein the overall structure of said polarization splitter is suitable for mounting the splitter in the optical system and wherein the splitter comprises a substrate having a thickness T such that the astigmatism introduced by the splitter when mounted at its tilted angle using said overall structure is less than or equal to D.

11. The optical system of claim 10 wherein D is approximately 0.05 millimeters.

12. The optical system of claim 10 wherein T is approximately 0.15 millimeters.

13. The optical system of claim 10 wherein the polarization splitter is tilted at an angle of approximately 45°

.

14. The optical system of claim 10 wherein the polarization splitter is a wire grid polarizer.

15. The optical system of claim 10 wherein the polarization splitter comprises a polarization coating.

16. The optical system of claim 10 wherein the polarization splitter comprises a polarizing birefringence film.

17. The optical system of claim 10 wherein the light modulating panel is a reflective liquid crystal display.

18. The optical system of claim 10 wherein the light modulating panel is a liquid crystal on silicon panel.

19. The optical system of claim 10 further comprising a polarizer between the illumination system and the polarization splitter.

20. A polarization splitter comprising a substrate whose thickness is less than or equal to 0.15 millimeters, wherein the overall structure of said splitter is suitable for mounting the splitter in an optical system and, when mounted at 45 degrees in air using said overall structure and transmitting divergent light, the splitter generates less than 0.05 millimeters of astigmatism.

21. The polarization splitter of claim 20 wherein the splitter is a wire grid polarizer.