Single-path color video projection systems employing reflective liquid crystal display devices

• US 20030214617A1
• Filed: 05/17/2002
• Published: 11/20/2003
• Est. Priority Date: 05/17/2002
• Status: Active Grant

• Current Assignee: Straight Signals LLC (Intellectual Ventures LLC)
• Original Assignee: Straight Signals LLC (Intellectual Ventures LLC)
• Inventors: Bierhuizen, Serge, Gianola, Lawrence J., Svardal, Benny S.
• Granted Patent: US 6,839,095 B2
• Time in Patent Office: Days
• US Class Current: 349/113
• CPC Class Codes: G03B 21/006 using LCD's

Abstract

A multimedia projector (100) includes a single-path frame-sequential color optical system in which light rays emitted by a light source (14) propagate through a color wheel (102) and an optical integrator (16, 120, 122), and are directed toward a transflective polarizing beam splitter (40) that separates them into P-polarized components (76) and S-polarized components (78). The P-polarized components are transmitted toward a reflective LCD (26) in which pixels in a dark state reflect the light rays without a polarization change and return them through the transflective polarizing beam splitter, whereas pixels in a bright state reflect the light rays with a 90° polarization change as S-polarized light rays (112), which are reflected by the transflective polarizing beam splitter toward a projection lens (27).

Claims

1. A frame-sequential color (“

FSC”

) video display system, comprising;

a light source from which polychromatic light propagates;

a color modulation device receiving the polychromatic light and propagating FSC light;

a plate-type transflective polarizing beam splitter receiving the FSC light, transmitting rays of the FSC light polarized in a first polarization direction, and reflecting rays of the FSC light polarized in a second polarization direction; and

a reflective liquid crystal light valve receiving the FSC light polarized in the first polarization direction, the reflective liquid crystal light valve including pixels selectively switchable between first and second states such that pixels switched to the first state reflect the FSC light in the first polarization direction back through the transflective polarizing beam splitter, and pixels switched to the second state reflect the FSC light in the second polarization direction for reflection off the transflective polarizing beam splitter as image bearing light.

2. The apparatus of claim 1, in which the display system comprises a projection display that further includes a projection lens through which the image bearing light propagates.

3. The apparatus of claim 2, further including a light polarizing filter disposed between the transflective polarizing beam splitter and the projection lens to correct for non-ideal light transmission and reflection responses of the transflective polarizing beam splitter.

4. The apparatus of claim 1, in which the plate-type transflective polarizing beam splitter includes at least one of a wire grid device, a multi-layer thin film device, a cholesteric polymer liquid crystal device, and a laminated polymer sheet device.

5. The apparatus of claim 1, further including a polarization conversion device that polarizes the FSC light to substantially the first polarization direction.

6. The apparatus of claim 5, in which the polarization conversion device includes at least one of a polarization conversion prism assembly and a polarization conversation assembly.

7. The apparatus of claim 1, further including at least one of an optical integrator and a flyseye lens array.

8. The apparatus of claim 7, in which the light source includes a collimating reflector that is positioned close to the flyseye lens array.

9. The apparatus of claim 1, in which the color modulation device includes one of a color wheel and a liquid crystal-based color-switching device.

10. The apparatus of 9, in which the polychromatic light is focused through the color wheel by an aspherical corrector lens and the FSC light emerging from the color wheel is collimated with an aspherical lens for propagation through a light homogenizing flyseye lens array.

11. The apparatus of claim 10, in which the reflective liquid crystal light valve has an aspect ratio, and in which the FSC light propagated through the light homogenizing flyseye lens array further has a cross-sectional aspect ratio that substantially matches the aspect ratio of the reflective liquid crystal light valve.

12. A frame-sequential color (“

FSC”

) video display apparatus, comprising;

a reflector having first and second focal points;

an arc lamp having an arc generating light rays emanating from the first focal point;

a compound parabolic concentrator (“

CPC”

) receiving the light rays at the second focal point;

a color modulation device receiving the light rays from the CPC and propagating FSC light;

a polarizing beam splitter receiving the FSC light, transmitting rays of the FSC light polarized in a first polarization direction, and reflecting rays of the FSC light polarized in a second polarization direction; and

reflective liquid crystal light valve receiving the FSC light polarized in the first polarization direction, the reflective liquid crystal light valve including pixels selectively switchable between first and second states such that pixels switched to the first state reflect the FSC light in the first polarization direction back through the polarizing beam splitter, and pixels switched to the second state reflect the FSC light in the second polarization direction for reflection off the polarizing beam splitter as image bearing light.

13. The apparatus of claim 12 in which the polarizing beam splitter includes a plate-type transflective polarizing beam splitter.

14. The apparatus of claim 12 in which the polarizing beam splitter includes a polarizing beam splitting prism.

15. The apparatus of claim 12, in which the arc lamp further includes a mirror coating on a surface facing away from the reflector to reflect light rays back through the arc to join with and further intensify the light rays emanating from the first focal point.

16. The apparatus of claim 12, in which the reflector is a double- paraboloid reflector.

17. The apparatus of claim 12 in which the light rays enter the CPC over a wide range of acceptance angles and exit the CPC at a substantially smaller exit angle, thereby establishing an É

tendue less than about 7 mm²•

st.

18. The apparatus of claim 12, in which the reflector has a light collecting efficiency greater than about 40 percent.