Two color liquid crystal light valve image projection system with single prepolarizer

• US 4,500,172 A
• Filed: 12/28/1981
• Issued: 02/19/1985
• Est. Priority Date: 12/28/1981
• Status: Expired due to Term

• Current Assignee: Victor Company of Japan Limited (JVC Kenwood Corporation)
• Original Assignee: Hughes Aircraft Company (Rtx Corporation)
• Inventors: Gagnon, Ralph J., Cedarstrom, Roy A.
• Primary Examiner(s): Corbin, John K.
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US06/334,679
• Time in Patent Office: 1,149 Days
• Field of Search: 350/331 R, 350/342, 350/345, 350/401, 350/403, 350/408, 353/31, 353/34, 353/37
• US Class Current: 349/9
• CPC Class Codes: H04N 9/31 Projection devices for colour picture display , e.g. using electronic spatial light modulators [ESLM]
• CPC Class Codes: H04N 9/3167 for polarizing the light beam polarizing optical systems per se G02B27/28

Abstract

An optical arrangement is disclosed which provides color selective prepolarization of the light incident upon two or more light valves. This is accomplished by the use of a prepolarizing prism which acts on light from a light source to direct light of a first polarization to a first dichroic separator and light of a second polarization to a second dichroic separator. Each separator transmits an output beam having substantially a single color and a single polarization state. The two resulting beams are recombined by a dichroic adder prior to being applied to a second polarizing prism. The second polarizing prism directs light of a first color and polarization to a first light valve and light a second color and polarization to a second light valve. The result is that one light valve sees light of a first color and a first polarization and the other light valve sees light of a second color and second polarization. Each light valve modulates the polarization state of incident light in accordance with the input or writing light. Where the writing light is present, the polarization state is changed from the first to the second or vice versa depending upon the light valve. The output of each light valve is applied to a second or main polarizing prism which converts the modulations of polarization into modulations of brightness. The output of the main polarizing prism is then applied to a projection lens in a conventional manner.

Claims

1. A two-color image projection system with prepolarization comprising:

a light source for providing light energy;

a prepolarizing beamsplitter for splitting and prepolarizing the light from the source into first and second beams having first and second polarization states respectively;

a first dichroic separator for extracting light of a first color from said first beam;

a second dichroic separator for extracting light of a second color from said second beam;

a dichroic adder for combining the first and second beams into a single beam;

a polarizer for splitting the single beam and reflecting light of the first color and polarization and transmitting light of the second color and polarization;

a first liquid crystal light valve for selectively modulating the polarization state of the light reflected by said polarizer from the first polarization state to the second polarization state;

a second liquid crystal light valve for selectively modulating the polarization state of the light transmitted by said polarizer from the second polarization state to the first polarization state; and

means for projecting light modulated by said first and second light valves.

2. The two-color image projection system of claim 1 wherein said prepolarizing beamsplitter is a bi-prism type polarizing beamsplitter.

3. A color selective prepolarizing system for liquid crystal light valve projectors comprising:

a prepolarizing beamsplitter for splitting and prepolarizing light from a source into first and second beams having first and second polarization states respectively;

first means for extracting light of a first color from said first beam;

second means for extracting light of a second color from said second beam; and

means for combining the first and second beams into a single beam having substantially two components, the first component having essentially light of a first color and first polarization state and the second component having essentially light of a second color and a second polarization state.

4. The color selective prepolarizing system of claim 3 wherein said first and second means includes dichroic separators.

5. The color selective prepolarizing system of claim 4 wherein said means for combining the first and second beams into a single beam includes a dichroic adder.