Lock-in CCD and the convolver CCD: applications of exposure-concurrent photocharge transfer in optical metrology and machine vision

摘要

Abstract: Two types of image sensors are described that exploitthe CCD's capability of spatially moving photochargesimultaneously with the exposure to a scene. Thelock-in CCD is a two- dimensional array of pixels, eachof which is a synchronous detector for oscillatingoptical wave fields with a spatially varyingdistribution of phase, amplitude and background offset.Main applications of this novel CCD type are intime-of-flight and heterodyne interferometric rangeimaging without moving parts. The convolver CCDconsists of a two-dimensional array of pixels,connected with their nearest neighbors through shortCCD lines, with which photocharge can be transferredvertically and horizontally during the exposure. Bysuitably timing these charge shifts, freelyprogrammable convolutions with kernels of arbitrarysize become possible. Tap weight accuracies oftypically 2% of the largest tap value have beenobtained for a variety of linear filters that arecommonly used in machine vision. An integral part ofthese CCDs is a programmable, microcontroller-baseddriver system, capable of generating dynamic pulsesequences and driving virtually any image sensoravailable commercially or custom designed for specialapplications. !23