Reflective LCD projection system using wide-angle Cartesian polarizing beam splitter

• US 6,486,997 B1
• Filed: 05/17/1999
• Issued: 11/26/2002
• Est. Priority Date: 10/28/1997
• Status: Expired due to Fees

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Boyd, Gary T., Bruzzone, Charles L., Weber, Michael F., Eckhardt, Stephen K., Strharsky, Roger J., Aastuen, David J. W.
• Primary Examiner(s): Shafer, Ricky D.
• Application Number:
  US09/312,917
• Time in Patent Office: 1,289 Days
• Field of Search: 359/247, 359/250, 359/252, 359/253, 359/256, 359/486, 359/487, 359/495, 359/497, 359/498, 359/500, 349/5, 349/9, 353/20, 353/81
• US Class Current: 359/247
• CPC Class Codes: B29C 55/023 using multilayered plates or sheets
• CPC Class Codes: B29D 11/00 Producing optical elements, e.g. lenses or prisms grinding or polishing of optical elements B24B; constructional form of optical elements G02B; optical parts of spectacles G02C7/00
• CPC Class Codes: B29K 2995/003 Reflective
• CPC Class Codes: B29K 2995/0034 Polarising
• CPC Class Codes: B32B 27/36 comprising polyesters
• CPC Class Codes: G02B 27/1026 for use with reflective spatial light modulators
• CPC Class Codes: G02B 27/123 The splitting element being a lens or a system of lenses, including arrays and surfaces with refractive power
• CPC Class Codes: G02B 27/143 using macroscopically faceted or segmented reflective surfaces
• CPC Class Codes: G02B 27/145 having sequential partially reflecting surfaces
• CPC Class Codes: G02B 27/149 using crossed beamsplitting surfaces, e.g. cross-dichroic cubes or X-cubes
• CPC Class Codes: G02B 27/283 used for beam splitting or combining
• CPC Class Codes: G02B 5/305 including organic materials, e.g. polymeric layers
• 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: H04N 9/3105 for displaying all colours simultaneously, e.g. by using two or more electronic spatial light modulators simultaneous projection in colour photography G03B33/10; beam splitting or combining systems per se G02B27/10
• CPC Class Codes: H04N 9/3167 for polarizing the light beam polarizing optical systems per se G02B27/28

Abstract

An optical imaging system including a wide-angle Cartesian polarizing beam splitter, light valve illumination optics having an f/#≦2.5, and at least one reflective light valve. The Cartesian polarizing beam splitter (PBS) has a structural orientation defining fixed polarization axes. The use of a Cartesian PBS allows the development of systems using curved PBS that provide higher light output and/or replace or augment other optical components. By recognizing and advantageously applying properties of wide-angle Cartesian polarizers, the present invention discloses a high-efficiency optical imaging system capable of functioning at f/#'"'"'s equal to or below f/2.5 while maintaining a contrast ratio of at least 100 to 1, or, more preferably, 150 to 1 in a projection system configuration.

Claims

1. An optical imaging system comprising:

a) a wide-angle Cartesian polarizing beam splitter, the polarizing beam splitter having a structural orientation defining fixed axes of polarization;

b) at least one reflective light valve, wherein the polarizing beam splitter splits incident light into a first and a second substantially polarized beam having polarization states referenced to the fixed coordinate system and wherein the polarizing beam splitter directs the first polarized beam onto the reflective light valve; and

c) light valve illumination optics illuminating the at least one reflective light valve via the polarizing beam splitter with light having an f/# equal to or less than 2.5 and wherein the optical imaging system has a dynamic range of at least 100 to 1 over projected color bands in the visible light range.

2. The optical imaging system of claim 1, wherein the system has a minimum acceptance cone angle of about 12 degrees.

3. The optical imaging system of claim 1, wherein the dynamic range exceeds 150 to 1.

4. The optical imaging system of claim 1, the light valve illumination optics having an f/# of at most 2.0.

5. The optical imaging system of claim 4, wherein the dynamic range exceeds 150 to 1.

6. The optical imaging system of claim 1, wherein the light valve is a polarization modulating light valve.

7. The optical imaging system of claim 1, wherein the reflective light valve is a smectic liquid crystal light valve.

8. The optical imaging system of claim 7, wherein the reflective light valve is an FLCD.

9. The optical imaging system of claim 1, wherein the reflective light valve is a nematic liquid crystal light valve.

10. The optical imaging system of claim 1, further comprising a quarter-wave compensator located optically between the Cartesian polarizing beam splitter and the reflective light valve.

11. The optical imaging system of claim 1, further comprising a pre-polarizer, wherein the pre-polarizer polarizes input light into pre-polarized light, wherein the pre-polarized light comprises the incident light on the polarizing beam splitter.

12. The optical imaging system of claim 1, further comprising a color separation and recombination prism and a plurality of reflective light valves, wherein the prism receives the polarized light from the polarizing beam splitter, color separates the polarized light and directs polarized color beams to each light valve.

13. The optical imaging system of claim 1, wherein the reflective light valve reflects at least a portion of the first polarized beam back to the Cartesian polarizing beam splitter.

14. The optical imaging system of claim 1, wherein the first polarized beam has a principal ray and the light valve has reflective surface defining a reflective plane, wherein the principal ray is normal to the reflective plane.

15. The optical imaging system of claim 1, further comprising a second Cartesian polarizing beam splitter, wherein the reflective light valve reflects at least a portion of the first polarized beam to the second beam splitter.

16. The optical imaging system of claim 1, wherein the Cartesian polarizing beam splitter comprises a multi-layer birefringent film.

17. The optical imaging system of claim 1, wherein the polarizing beam splitter comprises a multi-layer polymeric film.

18. The optical imaging system of claim 1, wherein the polarizing beam splitter comprises a wire grid polarizer.

19. The optical imaging of claim 1, the illumination optics having an f/# equal or less than 1.8.

20. The optical imaging system of claim 1, the Cartesian polarizing beam splitter having a rotation axis and a Material Axis along which light reflected by the Cartesian polarizing beam splitter is substantially polarized, wherein the rotation axis is oriented parallel to the Material Axis.

21. The optical imaging system of claim 1, wherein the Cartesian polarizing beam splitter is curved along at least one axis.

22. The optical imaging system of claim 1, wherein the principal ray of the incident light is incident on the Cartesian polarizing beam splitter at an angle between 40°

and 50°

.

23. An optical imaging system as recited in claim 1, wherein the wide angle, Cartesian polarizing beamsplitter maintains the dynamic range of at least 100 to 1 in each projected color band for a cone of incident light defining the f/# of 2.5 or less.

24. An optical system comprising:

at least one reflective light valve for reflecting a two dimensional image;

light valve illumination optics producing an illuminating beam of light incident on the at least one reflective light valve with an f/# of no more than 2.5; and

a wide angle, Cartesian polarizing beamsplitter disposed between the at least one light valve and the light valve illumination optics so that the illuminating beam passes to the at least one light valve via the wide angle Cartesian polarizing beamsplitter in a first polarization state;

wherein image light modulated by the at least one light valve is passed via the wide angle Cartesian polarizing beamsplitter in a second polarization state orthogonal to the first polarization state, and has a dynamic range of at least 100;

1 in each projected color band.

25. An optical system as recited in claim 24, wherein the wide angle, Cartesian polarizing beamsplitter reflects light in a cone having the f/# of no more than 2.5 while maintaining the dynamic range of at least 100:

1 in each projected color band.