Cholesteric polarizer for liquid crystal display and overhead projector
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United States of America Patent
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Jun 28, 1994
Grant Date -
N/A
app pub date -
Dec 31, 1992
filing date -
Dec 31, 1992
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
A liquid crystal display (LCD) panel employs a cholesteric polarizer which passes light of a first circular polarization, but reflects light of a second circular polarization. The LCD panel may be monochrome or color; in the color embodiments, several different color filters are used, each having one or more cholesteric polarizers tuned to a specific bandwidth in the visible spectrum. These polarizers replace dyed (neutral or dichroic) polarizers of prior art LCD panels, and provide improved color purity. The invention may be enhanced by providing a light recycling scheme whereby the handedness of the circularly polarized light reflected by the polarizers is changed and redirected back to the polarizers. This recycling scheme may also be adapted to provide an overhead projector having a high output polarized light source, particularly useful in conjunction with an LCD panel.
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