Charge coupled device incorporating laplacian thresholding with tdi array

Abstract

A CCD imaging array is operated in a time delay and integration mode to generate an array of charge packets corresponding to the light intensity at the picture elements of an irradiating image. The charge packets from the imaging array are gated in parallel to a line image storage array that stores n rows of charge packets in a columnar relation. A replicator circuit generates a replicated sum charge for each column of charge packets of the line image storage array. Each replicated sum charge corresponds to the sum of the n charges stored in a column at a particular instant in time and the charge stored at the (n+1)/2 position of each column is the middle charge for the associated replicated sum charge. Parallel delay gating electrodes gate a row of replicated sum charges to an area average serial shift register at the same time that a row of corresponding middle charges is gated into a focused element serial shift register. The serial shift registers are gated synchronously in a serial fashion and, as the registers are gated, the endmost n replicated sum charges are summed by a horizontal summer and 1/n.sup.2 of the sum is subtracted by a comparator from an associated central charge stored in the focused element serial shift register. The difference is the Laplacian for the central charge. The output of the focused element serial shift register, the summer output, and the Laplacian are useful for subsequent image processing.