Liquid crystal light valve projector with improved contrast ratio and with 0.27 wavelength compensation for birefringence in the liquid crystal light valve
First Claim
1. 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,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 liquid crystal light valve means and back through said compensator means to said polarization means wherein said compensator means has shifted the polarization of said reflected light so that said reflected light has a phase shift in its polarization of approximately 180°
; 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.
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Accused Products
Abstract
In a liquid crystal light valve projector, a quarter-wave compensator plate is disposed between a polarization plate and a liquid crystal light valve to compensate for polarization irregularities induced by the off-incident reflections in the cone of light projected onto the LCLV. The quarter-wave compensation plate reverses the phase of the P component of said illumination light with respect to said compensator plate by 180° thereby eliminating P-polarization leakage during the dark state of an LCLV projector. The invention also combines the compensator plate with a heat shield and a low stress-optical coefficient counter electrode substrate to reduce the birefringence of the LCLV thereby also minimizing leakage of P-polarized light onto the projection screen during the dark state of the projector.
245 Citations
16 Claims
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1. A polarization based projection system comprising:
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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, 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 liquid crystal light valve means and back through said compensator means to said polarization means wherein said compensator means has shifted the polarization of said reflected light so that said reflected light has a phase shift in its polarization of approximately 180°
; andwherein 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. - View Dependent Claims (2)
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3. A polarization based projection system comprising:
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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°
; andwherein 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. - View Dependent Claims (4)
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5. A polarization based projection system comprising:
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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. - View Dependent Claims (6, 7, 8, 9, 10, 11)
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12. A polarization based projection system comprising:
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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. - View Dependent Claims (13, 14, 15, 16)
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Specification