High efficiency optical tank for three color liquid crystal light valve image projection with color selective prepolarization

• US 4,461,542 A
• Filed: 12/28/1981
• Issued: 07/24/1984
• Est. Priority Date: 12/28/1981
• Status: Expired due to Term

• Current Assignee: JVC Americas Corporation (JVC Kenwood Corporation)
• Original Assignee: Hughes Aircraft Company (Rtx Corporation)
• Inventors: Gagnon, Ralph J.
• Primary Examiner(s): Corbin, John K.
• Assistant Examiner(s): Lewis, David
• Application Number:
  US06/334,680
• Time in Patent Office: 939 Days
• Field of Search: 350/342, 350/345, 350/331 R, 350/401, 350/403, 350/408, 353/31, 353/34, 353/37, 358/60, 358/61
• US Class Current: 349/8
• CPC Class Codes: H04N 9/3167 for polarizing the light beam polarizing optical systems per se G02B27/28

Abstract

A first color selective beam splitter is provided for splitting light from a source into first and second beams, the first beam being blue and the second beam having red and green color components.

A second beam splitter is provided for directing light of the first beam to a blue liquid crystal light valve. The light valve modulates the polarization of the light in the first beam and returns it to the second beam splitter which converts the modulations of polarization to modulations of intensity in the conventional manner and reflects it to a first projection lens.

A third beam splitter is provided for splitting the second beam into third and fourth beams having first and second polarization states, respectively. The third beam is reflected to a red filter. The fourth beam is transmitted through a green filter.

The output of each filter is a substantially monochromatic beam of a single polarization state. The filter outputs are recombined into a single beam which illuminates a fourth beam splitter. The fourth beam splitter is a main polarizing prism. It reflects light of the first polarization state to the green light valve and transmits light of the second polarization state to the red light valve. The light valves modulate the polarization state of incident light in the conventional manner and return it to the main prism. The main prism recombines the light from the first and second light valves into a single beam which is directed to a second projection lens.

Claims

1. A unitary optical arrangement comprising:

a first beamsplitter which splits incident light passing through a first surface into first and second beams, said first beam having a first color component and said second beam having second and third color components, respectively;

a second beamsplitter mounted in optical alignment with said first beamsplitter which directs light of said first color to a second surface and modulated light from said second surface to a third surface;

a third beamsplitter in optical alignment with said first beamsplitter which splits said second beam into third and fourth beams having first and second polarization states, respectively;

a first filter which transmits light of the second color in the third beam to provide an output beam having the second color and the first polarization state;

a second filter which transmits light of the third color in said fourth beam to provide an output beam having the second polarization state and the third color;

means for combining the outputs of said first and second filters into a fifth beam; and

a fourth beamsplitter which directs light in the fifth beam of the first polarization state a fourth surface, light of the second polarization state to a fifth surface and modulated light from said fourth and fifth surfaces to a sixth surface.

2. A multi-color image projection system comprising:

first means for providing a source of light energy;

first, second and third liquid crystal light valves;

first, second and third means for providing an optical input signal for use in combination with said first, second and third liquid crystal light valves;

first and second projection lens; and

a unitary optical arrangement including;

a first beamsplitter which splits incident light from said source into first and second beams, said first beam having a first color component and said second beam having second and third color components, respectively;

a second beamsplitter mounted in optical alignment with said first beamsplitter which directs light of said first color to said first light valve and modulated light from said first light valve to said first projection lens;

a third beamsplitter in optical alignment with said first beamsplitter which splits said second beam into third and fourth beams having first and second polarization states respectively;

a first dichroic filter which transmits light of the second color in the third beam to provide an output beam having the second color and the first polarization state;

a second dichroic filter which transmits light of the third color in the fourth beam to provide an output beam having the second polarization state and the third color;

means for combining the outputs of said first and second dichroic filters into a fifth beam;

a fourth beamsplitter which directs light in the fifth beam of the first polarization state to the second light valve, light of the second polarization state to the third light valve and modulated light from said second and third light valves to the second projection lens.

3. The optical arrangement of claim 2 wherein the first and third beamsplitters have parallel transverse axes relative to which the transverse axes of the second and fourth beamsplitters are oriented at an angle of 90°

.

4. The optical arrangement of claim 3 wherein the beamsplitters, separators and means for combining are coupled through oil.

5. The optical arrangement of claim 2 wherein said means for providing an optical input signal include cathode ray tubes.