Tdm-input electrometer, as in a line transfer ccd imager, using a charge

Abstract

A tendency towards uneven delays in raster scan lines is characteristic of known CCD imagers of line transfer type. This tendency arises owing to a line register being used for the time-division-multiplex selection of rows of charge packets sampling lines of image, and can be compensated to a degree by adjusting the onset of read-out of those rows. This tendency towards shear distortion of the television image is eliminated in the disclosed invention by replacing the line register with a charge funnel structure. The charge funnel is a CCD charge transfer channel, wide enough at its input to mate to the output ends of charge transfer channels in the imager register from which it receives charge packets in one or two rows at a time, and narrow enough at its output to increase the in-channel potential variations owing to charge packet transfer therethrough. This increase permits sensitive indications of charge level to be made by an electrometer. The electrometer (e.g., one of floating-diffusion type) supplies these indications as the CCD imager output signal.