A plurality of storage pixels within each unit pixel are arranged successively so that signal electrons for each storage pixel are moved independently through the storage pixels. Signal electrons newly generated in a photosensitive pixel are added to relevant signal electrons among the signal electrons moved independently through the storage pixels. That is, signal electrons generated in the photosensitive pixel for each of highly relevant frames are superimposed in the same storage pixel and stored in each storage pixel. The signal electrons stored in each storage pixel are subsequently amplified in and outputted from an output amplifier only once. Thus, read noise occurs only once at the output amplifier, to obtain images of high signal-to-noise ratio.
