US 6,636,276 B1Granted

Projection display system with at least two reflective light valves

AssigneeInternational Business Machines Corporation

InventorAlan Edward Rosenbluth

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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.

Claims40

Dependent claims

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.

5 more elements

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.

9 more elements

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.

5 more elements

Dependencies are inferred from the claim text.