Minnesota Mining and Manufacturing Company

Gary L Tritle

James K Kennedy

Michael C Sweaton

Stephen J Willett

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.

Cholesteric polarizer for liquid crystal display and overhead projector

An overhead projector (OHP) presentation system uses a liquid crystal display (LCD) panel to project electronically stored graphic images. The OHP preferably includes an integrated computer having a plurality of output ports for connection to various peripheral devices. A novel interface card is also used to provide electrical connections between the computer and the LCD panel, providing the further benefit of aligning the transmissive portion of the panel with the stage of the OHP. The LCD panel may be designed to swing horizontally into the optical path. This may be accomplished by providing a sliding drawer which inserts the panel within the body of the OHP, or by pivotally attaching the panel to the stage of the OHP.

Overhead projector for LCD panel

An overhead projector (OHP) presentation system uses a liquid crystal display (LCD) panel to project electronically stored graphic images. The OHP preferably includes an integrated computer having a plurality of output ports for connection to various peripheral devices. A novel interface card is also used to provide electrical connections between the computer and the LCD panel, providing the further benefit of aligning the transmissive portion of the panel with the stage of the overhead projector.

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Lakeway, TX, United States of America

Gary L Tritle