Importance

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Abstract

This light modulating device comprises three subsystems: an electron gun which produces a scanning constant intensity electron beam, a liquid crystal cell, and an appropriate optical system to deliver light to and from the modulating effects of the liquid crystal cell. The modulation is accomplished by utilizing a scanning constant intensity electron beam to deposit electrical charge through a secondary emission process on the dark side of a dielectric mirror within the liquid crystal cell, the amount of charge deposited being dependent upon the video voltage at the transparent electrode of the cell which is applied in synchronism with the scanning electron beam. In this manner a charge distribution is written on the back of the dielectric mirror which now contains all of the information within the video signal. The electrical field arising from this charge distribution in turn modulates the birefringence across the nematic phase liquid crystal. Under appropriate electrical field conditions, the 'twisted' nematic phase liquid crystal cell will reflect incident plane polarized light as eliptically polarized light constituting an 'ON' state. This elliptically polarized light is then projected through an appropriate analyzer and on through further relay optics. In the 'OFF' state incident plane polarized light is reflected from the cell as linearly polarized light and is blocked by the analyzer.

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First Claim