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Abstract

An optical beam scanner or spoiler includes an array of electrically controlled liquid crystal phase shifters. Each element of the phase shifter includes an active region where proper phase shift occurs, and also includes another region, generally near the edges of the element, in which light transmission does not occur or in which improper modulation results. The inefficient regions reduce the light transmission or modulation efficiency of the array. An aperture illuminator includes a Talbot plane phase plate (also known as a Fresnel image phase plate) interposed between the incident light beam and the liquid crystal array. The phase plate includes a transparent substrate with a binary pattern of regions of relatively higher and lower index of refraction in a repeating pattern with a period P. In a particular embodiment of the invention, the regions are physically raised and lowered portions of a surface. The phase plate generates an interference pattern of energy maxima and minima, and is located so the maxima fall on the active regions of the liquid crystal array, and the minima on the inactive portions. A second phase plate similar to the first (or a second pass through the first phase plate in a reflective system) reduces the magnitude of far-field grating lobes created by the first phase plate.

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First Claim