Projection display system with at least two reflective light valves

• US 6,636,276 B1
• Filed: 09/09/1999
• Issued: 10/21/2003
• Est. Priority Date: 09/09/1999
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Rosenbluth, Alan Edward
• Primary Examiner(s): Kim, Robert H.
• Assistant Examiner(s): SCHECHTER, ANDREW M
• Application Number:
  US09/392,957
• Time in Patent Office: 1,503 Days
• Field of Search: 349/5, 349/8, 349/9, 353/39, 353/33, 353/20
• US Class Current: 349/8
• CPC Class Codes: H04N 9/3117 by using a sequential colour filter producing two or more colours simultaneously, e.g. by creating scrolling colour bands

Abstract

A projection display system includes a light source, wavelength-selective retarder device, first and second reflective light valves (LVs), a polarizing beam splitter (PBS), and a wavelength-selective filtering device. The wavelength-selective retarder device receives a uniformly polarized light from the light source and produces a first dark-state light having a first polarization state at a first set of wavelengths and a second dark-state light having a second polarization state at a second set of wavelengths. The first LV receives the first dark-state light and produces a first bright-state light by rotating the polarization from the first polarization state to the second polarization state. The second LV receives the second dark-state light and produces a second bright-state light by rotating the polarization from the second polarization state to the first polarization state. The PBS, positioned between the wavelength-selective retarder device and the first and second LVs, directs the first and second dark-state lights to the first and second LVs respectively, and also directs the first and second bright-state lights to a screen. A wavelength-selective filtering device receives the first and second bright-state lights from the PBS and substantially reduces a residual dark-state light.

Claims

1. A projection display system comprising:

a light source adapted to supply an illumination light having common polarization at first and second sets of wavelengths;

a wavelength-selective retarder device positioned to receive said illumination light from said light source and to produce a first dark-state light having a first polarization state at said first set of wavelengths and a second dark-state light having a second polarization state at said second set of wavelengths;

a first reflective light valve device, comprising one or more light valves, adapted to receive said first dark-state light and to produce a first bright-state light by rotating the polarization from said first polarization state to said second polarization state;

a second reflective light valve device, comprising one or more light valves, adapted to receive said second dark-state light and to produce a second bright-state light by rotating the polarization from said second polarization state to said first polarization state;

wherein the assignment of said first and second sets of wavelengths to said first and second reflective light valve devices is switched sequentially in time;

a light splitting and combining device positioned between said wavelength-selective retarder device and said first and second reflective light valve devices, said light splitting and combining device adapted to receive said first and second dark-state lights from said wavelength-selective retarder device and to direct said first and second dark-state lights to said first and second reflective light valve devices respectively, and adapted to receive said first and second bright-state lights reflected from said first and second reflective light valve devices respectively and to direct said first and second bright-state lights as a combined beam to a screen; and

a wavelength-selective filtering device positioned to receive said combined beam containing said first and second bright-state lights from said light splitting and combining device and to substantially eliminate a residual dark-state light from said first and second light valve devices, wherein the wavelength-selective filtering device passes a beam containing all of red, blue and green primary color components of a color image which is projected onto the screen with improved contrast.

2. The projection display system of claim 1, said wavelength-selective retarder device comprising a wavelength-selective retarder adapted to rotate the polarization of said illumination light at either said first or second sets of wavelengths by 90 degrees.

3. The projection display system of claim 1, said wavelength-selective filtering device comprising:

a wavelength-selective retarder adapted to rotate the polarization of either said first or second bright-state light by 90 degrees so that the said first and second bright-state lights have a common polarization, and a

a linear polarizer following said wavelength-selective retarder and adapted to substantially eliminate a light having a polarization orthogonal to the common polarization.

4. The projection display system of claim 1, said wavelength-selective filtering device comprising a first wavelength-selective polarizer adapted to block a light having said second polarization state at said second set of wavelengths while passing other lights having a polarization different from said second polarization or having a wavelength out of said second set of wavelengths.

5. The projection display system of claim 4, said wavelength-selective filtering device further comprising a second wavelength-selective polarizer adapted to a block a light having said first polarization state at said first set of wavelengths while passing other lights having a polarization different from said first polarization or having a wavelength out of said first set of wavelengths.

6. The projection display system of claim 1, wherein said wavelength-selective retarder device comprises a retarder stack adapted to rotate the polarization of said illumination light at either said first or second sets of wavelengths by 90 degrees, said retarder stack being followed by a wavelength-selective polarizer adapted to block a light having said second polarization at said first set of wavelengths, and said wavelength-selective filtering device comprises a wavelength-selective linear polarizer adapted to block a light having said second polarization at said second set of wavelengths, said wavelength-selective polarizer being followed by a combination of a dichroic retarder adapted to rotate the polarization of either said first or second bright-state light by 90 degrees so that said first and second bright-state lights have a common polarization, and a linear polarizer adapted to substantially eliminate a light having a polarization orthogonal to the common polarization.

7. The projection display system of claim 1, further comprising:

a first color filter positioned between said light splitting and combining device and said first reflective light valve device, said first color filter adapted to absorb a light having a wavelength within said second set of wavelengths while passing a light having a wavelength within said first set of wavelengths, and

a second color filter positioned between said light splitting and combining device and said second reflective light valve device, said second filter adapted to absorb a light having a wavelength within said first set of wavelengths while passing a light having a wavelength within said second set of wavelengths.

8. The projection display system of claim 1, wherein said light splitting and combining device includes:

a first face adapted to receive said illumination light from said light source;

a second face adapted to output said first and second bright-state lights;

a third face adapted to output said-first dark-state light directed to said first reflective light valve device and to receive said first bright-state light reflected from said first reflective light valve device, and

a fourth face adapted to output said second dark-state light directed to said second reflective light valve device and to receive said first bright-state light reflected from said second reflective light valve device.

9. The projection display system of claim 1, wherein said light source further comprises a time-sequential separation device to alternatively supply light in said first and second color bands in said first set of wavelengths to said light splitting and combining device.

10. The projection display system of claim 1, wherein said first and second reflective light valve devices each contain a single-illuminated light valve and comprise all light valves in the projection display system illuminated by said illumination light.

11. The projection display system of claim 1, wherein said wavelength-selective retarder device and said wavelength-selective filtering device are both positioned externally to said light splitting and combining device.

12. The projection display system of claim 1, wherein said light splitting and combining device combines said first and second bright-state lights using a combining element that reflects visible light in said second polarization state that is in said first set of wavelengths, and that reflects visible light in said first polarization state that is not in said first set of wavelengths, and that transmits light in said second polarization state that is not in said first set of wavelengths.

13. The projection display system of claim 1, wherein the projection display system comprises a maximum of one light splitting and combining device.

14. The projection display system of claim 1, wherein the projection display system comprises a maximum of three light splitting and combining devices.

15. A projection display system comprising:

a light source adapted to supply an illumination light having common polarization at first and second sets of wavelengths;

a wavelength-selective retarder device positioned to receive said illumination light from said light source and to produce a first dark-state light having a first polarization state at said first set of wavelengths and a second dark-state light having a second polarization state at said second set of wavelengths;

said wavelength-selective retarder device comprising

a tilted dichroic mirror,

a tilted quarterwave retarder stacked over said tilted dichroic mirror,

a tilted mirror stacked over said tilted quarterwave retarder,

an untilted wavelength-selective linear polarizer positioned between said tilted dichroic mirror and said light splitting and combining device;

a first reflective light valve device, comprising one or more light valves, adapted to receive said first dark-state light and to produce a first bright-state light by rotating the polarization from said first polarization state to said second polarization state;

a second reflective light valve device, comprising one or more light valves, adapted to receive said second dark-state light and to produce a second bright-state light by rotating the polarization from said second polarization state to said first polarization state;

a light splitting and combining device positioned between said wavelength-selective retarder device and said first and second reflective light valve devices, said light splitting and combining device adapted to receive said first and second dark-state lights from said wavelength-selective retarder device and to direct said first and second dark-state lights to said first and second reflective light valve devices respectively, and adapted to receive said first and second bright-state lights reflected from said first and second reflective light valve devices respectively and to direct said first and second bright-state lights as a combined beam to a screen; and

a wavelength-selective filtering device positioned to receive said combined beam containing said first and second bright-state lights from said light splitting and combining device and to substantially eliminate a residual dark-state light from said first and second light valve devices, wherein the wavelength-selective filtering device passes a beam containing all of red, blue and green primary color components of a color image which is projected onto the screen with improved contrast.

16. The projection display system of claim 15, said wavelength-selective filtering device comprising:

a wavelength-selective retarder adapted to rotate the polarization of either said first or second bright-state light by 90 degrees so that the said first and second bright-state lights have a common polarization, and

a linear polarizer following said wavelength-selective retarder and adapted to substantially eliminate a light having a polarization orthogonal to the common polarization.

17. The projection display system of claim 15, said wavelength-selective filtering device comprising a first wavelength-selective polarizer adapted to block a light having said second polarization state at said second set of wavelengths while passing other lights having a polarization different from said second polarization or having a wavelength out of said second set of wavelengths.

18. The projection display system of claim 15, said wavelength-selective filtering device further comprising a second wavelength-selective polarizer adapted to block light having said first polarization state at said first set of wavelengths while passing other lights having a polarization different from said first polarization or having a wavelength out of said first set of wavelengths.

19. The projection display system of claim 15, further comprising:

a first color filter positioned between said light splitting and combining device and said first reflective light valve device, said first color filter adapted to absorb a light having a wavelength within said second set of wavelengths while passing a light having a wavelength within said first set of wavelengths, and

a second color filter positioned between said light splitting and combining device and said second reflective light valve device, said second filter adapted to absorb a light having a wavelength within said first set of wavelengths while passing a light having a wavelength within said second set of wavelengths.

20. The projection display system of claim 15, wherein said light splitting and combining device includes:

a first face adapted to receive said illumination light from said light source;

a second face adapted to output said first and second bright-state lights;

a third face adapted to output said first dark-state light directed to said first reflective light valve device and to receive said first bright-state light reflected from said first reflective light valve device, and

a fourth face adapted to output said second dark-state light directed to said second reflective light valve device and to receive said first bright-state light reflected from said second reflective light valve device.

21. The projection display of claim 15, wherein at least either one of said first and second reflective light valve devices includes a plurality of reflective light valves.

22. The projection display system of claim 15, wherein said first set of wavelengths of said first dark-state light includes first and second color bands and said second set of wavelengths of said second dark-state includes a third color band.

23. The projection display system of claim 15, wherein said first and second reflective light valve devices each contain a single illuminated light valve and comprise all light valves in the projection display system illuminated by said illumination light.

24. The projection display system of claim 15, wherein said wavelength-selective retarder device and said wavelength-selective filtering device are both positioned externally to said light splitting and combining device.

25. The projection system of claim 15, wherein said combining device is a cube combiner comprising two cemented right angle prisms with combining coatings on each side of the cemented hypotenuse.

26. The projection display system of claim 15, wherein the projection display system comprises a maximum of one light splitting and combining device.

27. The projection display system of claim 15, wherein the projection display system comprises a maximum of three light splitting and combining devices.

28. A projection display system comprising:

a light source adapted to supply an illumination light having common polarization at first and second sets of wavelengths;

a wavelength-selective retarder device positioned to receive said illumination light from said light source and to produce a first dark-state light having a first polarization state-at said first set of wavelengths and a second dark-state light having a second polarization state at said second set of wavelengths;

a first reflective light valve device, comprising one or more light valves, adapted to receive said first dark-state light and to produce a first bright-state light by rotating the polarization from said first polarization state to said second polarization state;

a second reflective light valve device, comprising one or more light valves, adapted to receive said second dark-state light and to produce a second bright-state light by rotating the polarization from said second polarization state to said first polarization state;

a light splitting and combining device positioned between said wavelength-selective retarder device and said first and second reflective light valve devices, said light splitting and combining device adapted to receive said first and second dark-state lights from said wavelength-selective retarder device and to direct said first and second dark-state lights to said first and second reflective light valve devices respectively, and adapted to receive said first and second bright-state lights reflected from said first and second reflective light valve devices respectively and to direct said first and second bright-state lights as a combined beam to a screen; and

wherein said light splitting and combining device combines said first and second bright-state lights using a combining element that reflects visible light in said second polarization state that is in said first set of wavelengths, and that reflects visible light in said first polarization state that is not in said first set of wavelengths, and that transmits light in said second polarization state that is not in said first set of wavelengths;

a wavelength-selective filtering device positioned to receive said combined beam containing said first and second bright-state lights from said light splitting and combining device and to substantially eliminate a residual dark-state light from said first and second light valve devices, wherein the wavelength-selective filtering device passes a beam containing all of red, blue and green primary color components of a color image which is projected onto the screen with improved contrast.

29. The projection display system of claim 28, said wavelength-selective retarder device comprising a wavelength-selective retarder adapted to rotate the polarization of said illumination light at either said first or second sets of wavelengths by 90 degrees.

30. The projection display system of claim 28, said wavelength-selective filtering device comprising:

a wavelength-selective retarder adapted to rotate the polarization of either said first or second bright-state light by 90 degrees so that the said first and second bright-state lights have a common polarization, and

a linear polarizer following said wavelength-selective retarder and adapted to substantially eliminate a light having a polarization orthogonal to the common polarization.

31. The projection display system of claim 28, wherein said wavelength-selective retarder device comprises a retarder stack adapted to rotate the polarization of said illumination light at either said first or second sets of wavelengths by 90 degrees, said retarder stack being followed by a wavelength-selective polarizer adapted to block a light having said second polarization at said first set of wavelengths, and said wavelength-selective filtering device comprises a wavelength-selective linear polarizer adapted to block a light having said second polarization at said second set of wavelengths, said wavelength-selective polarizer being followed by a combination of a dichroic retarder adapted to rotate the polarization of either said first or second bright-state light by 90 degrees so that said first and second bright-state light by 90 degrees so that said first and second bright light-state lights have a common polarization, and a linear polarizer adapted to substantially eliminate a light having a polarization orthogonal to the common polarization.

32. The projection display system of claim 28, further comprising:

a first color filter positioned between said light splitting and combining device and said first reflective light valve device, said first color filter adapted to absorb a light having a wavelength within said second set of wavelengths while passing a light having a wavelength within said first set of wavelengths, and

a second color filter positioned between said light splitting and combining device and said second reflective light valve device, said second filter adapted to absorb a light having a wavelength within said first set of wavelengths while passing a light having a wavelength within said second set of wavelengths.

33. The projection display system of claim 28, wherein said light splitting and combining device includes:

a first face adapted to receive said illumination light from said light source;

a second face adapted to output said first and second bright-state lights;

a third face adapted to output said first dark-state light directed to said first reflective light valve device and to receive said first bright-state light reflected from said first reflective light valve device, and

a fourth face adapted to output said second dark-state light directed to said second reflective light valve device and to receive said first bright-state light reflected from said second reflective light valve device.

34. The projection display of claim 28, wherein at least either one of said first and second reflective light valve devices includes a plurality of reflective light valves.

35. The projection display system of claim 28, wherein said first set of wavelengths of said first dark-state light includes first and second color bands and said second set of wavelengths of said second dark-state includes a third color band.

36. The projection display system of claim 28, wherein said first and second reflective light valve devices each contain a single illuminated light valve and comprise all light valves in the projection display system illuminated by said illumination light.

37. The projection display system of claim 28, wherein said wavelength-selective retarder device and said wavelength-selective filtering device are both positioned externally to said light splitting and combining device.

38. The projection system of claim 28, wherein said combining device is a cube combiner comprising two cemented right angle prisms with combining coatings on each side of the cemented hypotenuse.

39. The projection display system of claim 28, wherein the projection display system comprises a maximum of one light splitting and combining device.

40. The projection display system of claim 28, wherein the projection display system comprises a maximum of three light splitting and combining devices.