Reflective LCD projection system using wide- angle Cartesian polarizing beam splitter and color separation and recombination prisms

• US 20060098284A1
• Filed: 12/22/2005
• Published: 05/11/2006
• Est. Priority Date: 10/28/1997
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Bruzzone, Charles L., Aastuen, David J.W.
• Granted Patent: US 7,652,820 B2
• Time in Patent Office: Days
• US Class Current: 359/485.02
• CPC Class Codes: G02B 27/1026 for use with reflective spatial light modulators
• CPC Class Codes: G02B 27/145 having sequential partially reflecting surfaces
• 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: 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 an illumination system, a Cartesian PBS, and a prism assembly. The illumination system provides a beam of light, the illumination system having an f/# less than or equal to 2.5. The Cartesian polarizing beam splitter has a first tilt axis, oriented to receive the beam of light. A first polarized beam of light having one polarization direction is folded by the Cartesian polarizing beam splitter and a second polarized beam of light having a second polarization direction is transmitted by the Cartesian polarizing beam splitter. The Cartesian polarizing beam splitter nominally polarizes the beam of light with respect to the Cartesian beam splitter to yield the first polarized beam in the first polarization direction. The color separation and recombination prism is optically aligned to receive the first polarized beam. The prism has a second tilt axis, a plurality of color separating surfaces, and a plurality of exit surfaces. The second tilt axis may be oriented perpendicularly to the first tilt axis of the Cartesian polarizing beam splitter so that the polarized beam is nominally polarization rotated into the second polarization direction with respect to the color separating surfaces and a respective beam of colored light exits through each of the exit surfaces. Each imager is placed at one of the exit surface of the color separating and recombining prism to receive one of the respective beams of colored light, wherein each imager can separately modulate the polarization state of the beam of colored light.

Claims

1. A projection system comprising:

a) a Cartesian polarizing beam splitter, the Cartesian polarizing beam splitter defining a first tilt axis;

b) a color separation prism assembly, the prism assembly having a second tilt axis;

c) wherein the Cartesian polarizing beam splitter and the prism assembly are arranged such that the first and the second tilt axes are perpendicular to each other.

2. The projection system of claim 1, further comprising an illumination system providing a beam of light, the illumination system having an f/# less than or equal to 2.5.

3. The projection system of claim 1, wherein the projection system is a front projection system.

4. The projection system of claim 1, wherein the system is a rear projection system.

5. The projection system of claim 1, wherein the color separation prism assembly includes a Philips prism.

6. The projection system of claim 1, wherein the Cartesian polarizing beam splitter includes a multilayer optical film.

7. The projection system of claim 1, wherein the Cartesian polarizing beamsplitter is disposed so that illumination light reaching the color separation prism assembly via the Cartesian polarizing beamsplitter is in substantially the same polarization state across all color bands.

8. A projection system comprising:

a polarizing beam splitter, the polarizing beam splitter defining a first tilt axis; and

a color prism assembly, the color prism assembly having a second tilt axis, the polarizing beam splitter and the prism assembly being arranged so that the first tilt axis is perpendicular to the second tilt axis.

9. A system as recited in claim 8, wherein the polarizing beam splitter comprises a Cartesian polarizing beam splitter.

10. A system as recited in claim 8, further comprising an illumination system capable of providing a beam of light incident at the polarizing beamsplitter, the illumination system having an f-number less than or equal to 2.5.

11. The system of claim 8, wherein the projection system is a front projection system.

12. The system of claim 8, wherein the system is a rear projection system.

13. The system of claim 8, wherein the prism assembly comprises a Philips prism.

14. The system of claim 8, wherein the polarizing beam splitter comprises a multilayer optical film disposed between two prisms.

15. The system claim 8, further comprising a plurality of imagers, the color prism assembly having a plurality of transmissive surfaces and each imager of the plurality of imagers being aligned with respect to a corresponding transmissive surface of the prism assembly.

16. The system of claim 8, wherein the first tilt axis is perpendicular to a first reflection plane defined by a light ray incident at the polarizing beam splitter and a normal to a reflecting surface of the polarizing beamsplitter and the second tilt axis is perpendicular to a second reflection plane defined by a light ray incident at the color prism assembly a normal to a reflection surface of the color prism assembly.