Liquid crystal light valve projector with improved contrast ratio and with 0.27 wavelength compensation for birefringence in the liquid crystal light valve

A polarization based projection system comprising:

• an illumination source for providing illumination light,
• polarization means disposed adjacent to said illumination means for directing polarized light from said illumination source,
• liquid crystal light valve means disposed adjacent to said polarization means for receiving polarized light reflected from said polarization means, said liquid crystal light valve being capable of altering the polarization state of the polarized illumination light reflected from said polarization means,
• projection lens for projecting light transferred from said liquid crystal light valve means through said polarization means to said projection lens for projecting an image on a screen,
• said liquid crystal light valve means having a counter electrode means having low thermally induced stress birefringence and a low stress-optical coefficient,
• compensator means disposed between said polarization means and said liquid crystal light valve means for changing the phase angle of the polarized light reflected from said polarization means through said compensator means to said polarization means wherein said compensator means has shifted the P-polarization of said reflected light so that said reflected light has a phase shift in its P-polarization of approximately 180.degree.;
• and
• wherein said compensator means has a total retardance of greater than 0.25, wherein the additional retardance above 0.25 compensates for birefringence in the liquid crystal light valve means.

A polarization based projection system comprising:

• an illumination source for providing illumination light,
• polarization means disposed adjacent to said illumination means for directing polarized light from said illumination source,
• liquid crystal light valve means disposed adjacent to said polarization means for receiving polarized light reflected from said polarization means, said liquid crystal light valve being capable of altering the polarization state of the polarized illumination light reflected from said polarization means,
• projection lens for projecting light transferred from said liquid crystal light valve means through said polarization means to said projection lens for projecting an image on a screen,
• heat shield means located between said polarization means and said liquid crystal light valve means including an outer portion defining a first opening, said first opening for transmitting light to said light valve and said outer portion for absorbing stray light to reduce the temperature transferred to the liquid crystal light valve means thereby reducing the birefringence of said liquid crystal light valve means.

A polarization based projection system comprising:

• a source of light;
• polarization means for receiving said light and for producing polarized light therefrom;
• a light valve located adjacent said polarization means for modulating said polarized light;
• and
• a heat shield, located between said light valve and said polarization means and including an outer portion defining a first opening, said first opening for transmitting light to said light valve and said outer portion for absorbing stray light to reduce the temperature and birefringence of said light valve.