Patent ID: 6972810

Claim:
An optical system for use with a projection lens and an illumination system that produces randomly polarized light, said randomly polarized light comprising first, second, and third spectral portions, said optical system comprising: (a) a first polarization separator arranged to receive light from the illumination system and to separate that light into a first polarized component having a first polarization and a second polarized component having a second polarization, said second polarization being orthogonal to said first polarization; (b) a second polarization separator arranged to receive the first polarized component from the first polarization separator; (c) a first filter between the first polarization separator and the second polarization separator, said filter transmitting substantially only light of the first spectral portion to the second polarization separator; (d) a reflective liquid crystal device arranged to receive light of the first spectral portion from the second polarization separator, to modulate the polarization of said light on a pixel-by-pixel basis, and to reflect said light back to the second polarization separator; (e) a third polarization separator arranged to receive the second polarized component from the first polarization separator; (f) a second filter between the first polarization separator and the third polarization separator, said filter transmitting substantially only light of the second and third spectral portions to the third polarization separator; (g) a first polarization converting filter between the first polarization separator and the third polarization separator, said first polarization converting filter rotating the polarization of the second spectral portion by 90 degrees; (h) a reflective liquid crystal device arranged to receive light of the second spectral portion from the third polarization separator, to modulate the polarization of said light on a pixel-by-pixel basis, and to reflect said light back to the third polarization separator; (i) a reflective liquid crystal device arranged to receive light of the third spectral portion from the third polarization separator, to modulate the polarization of said light on a pixel-by-pixel basis, and to reflect said light back to the third polarization separator; (j) a fourth polarization separator arranged to: (A) receive polarization modulated light of the first spectral portion from the second polarization separator and polarization modulated light of the second and third spectral portions from the third polarization separator, and (B) provide said received polarization modulated light of the first, second, and third spectral portions to the projection lens; and (k) a second polarization converting filter between the third polarization separator and the fourth polarization separator, said polarization converting filter rotating the polarization of the second spectral portion by 90 degrees.