Charge-transfer-device planar array for detecting coherent-light phase

Abstract

Respective processors for pairs of photodetecting elements are included in an imager used for sensing hologram fringe patterns in an optical interferometer. These processors remove the direct-current pedestal from in-phase and quadrature-phase field images, then perform partial correlations of the resulting field images on a pixel-by-pixel basis, and then sum the partial correlations to complete the image correlation process and to provide imager output signal or the basis therefor. This localized processing greatly reduces the number of samples that have to be brought out of the imager each frame when the imager is used in an optical interferometer to detect phase modulation in an optical signal, allowing for increased frame rates in accordance with a further aspect of the invention. Image correlation is done according to a novel algorithm that avoids actually having to multiply together correspondingly located pixels in each pair of successive fields forming a successive non-overlapping frame. The multiplier-free processors are compact enough to be located within the solid state imager close to the pairs of photosensors they respectively serve in the imager.