This invention relates to a frame interline transfer (FIT) solid state image sensor of the type having an array of photosensitive elements for storing signal charges.
Solid state image sensors, such as charge coupled device (CCD) image sensors, employ an array of photosensitive elements for storing signal charges induced when exposed to light. The signal charges are transferred from the photosensitive elements to vertical shift registers provided for the photosensitive elements arranged in the respective vertical lines of the array. Clock pulses are applied in one direction to transfer the signal charges from the vertical shift registers for conversion into a video signal. Similar clock pulses are applied in the opposite direction to sweep the residual charges from the vertical shift registers before the next cycle of the signal charge transferring operation. It is preferable to improve the vertical resolving power by storing and reading one frame of signal charges rather than one field of signal charges during each cycle of signal charge transferring operation. One serious problem associated with such an image sensor is the tendency toward flicker noises which occur in a dark condition with no light incident on the photosensitive elements.