Abstract: Radiation illuminating the A register of a charge-coupled device (CCD) imager of the field transfer type during the transfer of a field from the A to the B register results in smear in the reproduced image. Such smear is reduced in a rear surface illuminated imager by forming a depletion region at said rear surface during the A to B transfer time. Charge carriers which are excited in the substrate during this period preferentially remain at the rear surface where they are passed to a drain rather than flowing to the potential wells whose contents are being shifted from the A to the B register.

Abstract: The input signal to a CCD register is sampled many times during one period of the multiple phase voltages employed to drive the CCD. The samples are translated to small charge packets which are added to one another during the one period to produce a sum charge packet which subsequently is propagated down the register. The higher frequency components, including noise, which are present in the input signal largely cancel during the charge addition process.