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

Claim 2

An image projection system characterized by a substantially unitary three-color light valve optical system with prepolarization.

Claim 3

The image projection system of Claim 1 further characterized by: a unitary optical arrangement comprising: a first color selective polarizing beamsplitter for splitting light from a source into first and second beams, said first beam consisting essentially of a first color and a first polarization state and said second beam consisting of second and third colors having the first polarization state and the first, second and third colors having the second polarization state; a second color selective polarizing beamsplitter for splitting said second beam into said third and fourth beams, said third beam consisting of essentially light of the first polarization state and said fourth beam consisting essentially of light of the second and third colors and the second polarization state; a first dichroic separator for filtering said third beam, extracting said first color component and directing it to said first light valve; and a second dichroic separator for filtering said fourth beam and directing said second ·color component to said second light valve and directing said third color component to said third light valve. 3. The image projection system of Claim 1 further characterized by: a source of light energy, three light valves, three cathode ray tubes, a projection lens, and a unitary optical arrangement; said arrangement comprising: a first color selective polarizing beamsplitter for splitting light from a source into first and second beams, said first beam consisting essentially of a first color and a first polarization state and said second beam consisting of second and third colors having the first polarization state and the first, second and third colors having the second polarization state; a second color selective polarizing beamsplitter for splitting said second beam into third and fourth beam, said third beam : consisting essentially of light of the first polarization state and said fourth beam consisting essentially of light of the second and third colors and the second polarization state; a first dichroic separator for filtering said third beam, extracting said first color component and directing it to said first light valve; a second dichroic separator for filtering said fourth beam and directing said second color component to said second light valve and directing said third color component to said third light valve, whereby first, second, and third substantially monochromatic polarization modulated beams are returned from said light valves and said first and second dichroic separators, respectively, to said second beamsplitter for recombination into a signal fifth beam which is directed thereby to said projection lens.

Claim 4

The optical arrangement of Claim 2 or 3 further characterized in that the first and second polarizing beamsplitters have transverse axes and each is mounted so that the beamsplitter transverse axes are oriented at a relative 90° angle.

Claim 5

The image projection system of Claim 1 further characterized by: a unitary optical arrangement comprising: a first beamsplitter for splitting incident light passing through a first aperture 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 for directing light of said first color to a second aperture and modulated light from said second aperture to a third aperture; a third beamsplitter in optical alignment with said first beamsplitter for splitting .said second beam into third and fourth beams having first and second polarization states, respectively; a first filter for transmitting 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 for transmitting light of the third color in said fourth beam to provide an output beam having the second polarization state and the third color; a beam combiner for combining the outputs of said first and second filters into a fifth beam; and a fourth beamsplitter for directing light in the fifth beam of the first polarization state, a fourth aperture, light of the second polarization state to a fifth aperture and modulated light from said fourth and fifth apertures to a sixth aperture.

Claim 6

In the image projection system of Claim 1 having a source of light energy; first, second and third liquid crystal light valves; first, second and third cathode ray tubes for use in combination with said first, second and third liquid crystal light valves; and first and second projection lens; 1 a unitary optical arrangement including: - a first beamsplitter for splitting 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 for directing 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 for splitting said second beam into third and fourth beams having first and second polarization states, respectively; a first dichroic filter for transmitting 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 for transmitting light of the third color in the fourth beam to provide an output beam having the second polarization state and the third color; a beam combiner for combining the outputs of said first and second dichroic filters · into a fifth beam; and a fourth beamsplitter for directing 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.

Claim 7

The optical arrangement of Claim 5 or 6 further characterized in that 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°.

Claim 8

The image projection system of the above claims further characterized in that the beamsplitters, separators and means for combining are coupled through oil.