Importance

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Abstract

A light valve comprises a pair of elements of transparent material each comprising a diffraction grating of like periodicity facing each other with parallel grating lines. Such a light valve is termed herein a bigrate. The transmission of light through the bigrate will depend on the relative position of the pair of gratings in the direction perpendicular to the grating lines and means may be provided for moving the elements relative to each other in that direction. One of the gratings may be embossed on a polyvinylidene fluoride (PVF.sub.2) strip and moved by piezoelectric means, which may be a portion of such a strip. One strip may then be moved relative to the other in response to an electrical signal to control the zero diffraction order light transmission from no transmission to full transmission, or any desired intermediate transmission. Two intersecting sets of polyvinylidene fluoride (PVF.sub.2) strips are arranged to form a matrix of bigrates, which, when uniformly illuminated produce a display of images, such as television images. In one set video signals produce motion perpendicular to the horizontal grating lines. The other set is made to move in a direction perpendicular to its surface in order to lock the strips of the first set in desired positions, or to unlock them, for example, a line at a time. Line-at-a-time TV signals may thus control the images. Three superimposed matrices each with diffraction lines of grating depth different from the others may provide color images.

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First Claim