Charge coupled device image sensors

Claim 1

A frame transfer CCD image sensor comprising: an image section comprising a photo-sensitive portion of an array of CCD channels; a store section comprising a non-photo-sensitive portion of said array of CCD channels; a line read-out section adjacent to the store section; a control electrode structure associated with said image, store and read-out sections; and means for applying pulses to the control electrode structure so as to transfer an image charge pattern generated in said image section along the channels into the store section, and to provide electrical signals representing charge stored in said store section by read-out via said read-out section wherein: the store section of the array has several more charge storage locations in each channel than the image sections of the array; said means for applying pulses applies to the electrode structure a sequence of pulses such that after each transfer of an image charge pattern generated in the image section to the store section several lines of charge storage locations in the store section are left between the image section and the charge pattern transferred to the store section which contain charge resulting only from frame shift smear and are otherwise substantially empty of charge; and means is provided for subtracting electrical signals representing an average of the charges in said several lines of charge storage locations from electrical signals read out from the store section via said read-out section, representing a said image charge pattern generated in said image section, thereby to cancel frame shift smear in said signals representing said image charge pattern, said charges in said several lines being accumulated in the read-out section of the sensor to obtain said average.