Polarization conversion system and method for stereoscopic projection

• US 20090128780A1
• Filed: 05/09/2008
• Published: 05/21/2009
• Est. Priority Date: 05/09/2007
• Status: Active Grant

• Current Assignee: RealD Incorporated
• Original Assignee: Real D
• Inventors: Robinson, Michael G., Schuck, Miller H., Sharp, Gary D.
• Granted Patent: US 8,727,536 B2
• Time in Patent Office: Days
• US Class Current: 353/20
• CPC Class Codes: G02B 13/00 Optical objectives specially designed for the purposes specified below with variable magnification in general G02B15/00
• CPC Class Codes: G02B 26/008 in the form of devices for effecting sequential colour changes, e.g. colour wheels
• CPC Class Codes: G02B 30/24 involving temporal multiplexing, e.g. using sequentially activated left and right shutters
• CPC Class Codes: G02B 30/25 using polarisation techniques
• CPC Class Codes: H04N 13/337 using polarisation multiplexing
• CPC Class Codes: H04N 13/341 using temporal multiplexing

Abstract

A polarization conversion system separates light from an unpolarized image source into a first state of polarization (SOP) and an orthogonal second SOP, and directs the polarized light on first and second light paths. The SOP of light on only one of the light paths is transformed to an orthogonal state such that both light paths have the same SOP. A polarization modulator temporally modulates the light on the first and second light paths to first and second output states of polarization. First and second projection lenses direct light on the first and second light paths toward a projection screen to form substantially overlapping polarization encoded images. The polarization modulator may be located before or after the projection lenses. The polarization-encoded images may be viewed using eyewear with appropriate polarization filters.

Claims

1. A polarization conversion system for transmitting polarization encoded imagery to a projection screen, comprising:

a first projection lens;

a second projection lens;

a polarization beam splitter operable to transmit light of a first polarization state toward the first projection lens on a first light path, and operable to reflect light of a second polarization state toward a second light path;

a reflecting element located on the second light path operable to reflect light toward the second projection lens; and

a polarization modulator located on the first and second light paths,

wherein the first and second projection lenses are operable to direct the polarization encoded images toward the projection screen.

2. The polarization conversion system of claim 1, further comprising a half wave plate located on one of the first and second light paths, and located ahead of the polarization modulator.

3. The polarization conversion system of claim 2, wherein the polarization modulator comprises:

a first polarization switch located on the first light path and after the first projections lens; and

a second polarization switch located on the second light path and after the second projections lens.

4. The polarization conversion system of claim 3, wherein the first and second polarization switches temporally modulate polarized light in synchronization.

5. The polarization conversion system of claim 2, wherein the polarization modulator comprises:

a first polarization switch located on the first light path and between the polarization beam splitter and the first projections lens; and

a second polarization switch located on the second light path and between the polarization beam splitter and the second projections lens.

6. The polarization conversion system of claim 1, wherein the polarization modulator comprises a single polarization switch.

7. The polarization conversion system of claim 2, wherein the polarization modulator comprises a liquid crystal based modulator.

8. The polarization conversion system of claim 1, wherein the polarization modulator comprises a rotating segmented polarizer wheel.

9. The polarization conversion system of claim 8, wherein the rotating segmented polarizer wheel comprises:

an isotropic segment; and

a rotator segment,

wherein the spinning wheel is operable to convert a polarized input to a set of temporally alternating orthogonally polarized output states.

10. The polarization conversion system of claim 1, further comprising an initial relay lens operable to direct unpolarized light from an image source toward the polarization beam splitter.

11. The polarization conversion system of claim 1, further comprising a first relay lens located on the first light path and operable to direct light toward the first projection lens, and a second relay lens located on the second light path and operable to direct light toward the second projection lens.

12. The polarization conversion system of claim 2, further comprising a pre-polarizer located before the polarization modulator.

13. The polarization conversion system of claim 1, wherein the reflecting element comprises one of a glass prism, a mirror, and a second polarization beam splitter.

14. A method for projecting polarization-encoded images, comprising:

receiving unpolarized image source light at a polarization beam splitter;

transmitting image source light of a first polarization state at the polarization beam splitter toward a projection lens located on a first light path;

reflecting image light of a second polarization state at the polarization beam splitter toward a second light path;

reflecting light on the second light path toward a second projection lens;