JPS6439176A - Solid state image pickup device - Google Patents

Abstract

PURPOSE:To obtain a solid state image pickup device of high sensitivity which can obtain an output signal having a high SN ratio and no after-image, by outputting the picture element optical signal with subtraction of the dark output signal stored in a frame memory when the picture element optical signal integrated for a fixed time is read. CONSTITUTION:A vertical scan circuit 113 of an image sensor 1 is actuated and a reset pulse and the read pulse set right after said reset pulse are applied to an SIT forming a picture element for each row line. The output signal read out at that point of time has an extremely short integration time and therefore regarded as a dark time output and the dark time output signals of each picture element equivalent to a single frame are written and stored into a frame memory 2. When a prescribed integration time Tint passed, the read pulse is applied again to the sensor 1 and the optical signal stored in each picture element is read out. At the same time, the dark time output signal is read out of the memory 2 in response to each picture element by the timing pulse given from a timing generator 5. Both the optical signal and the output signal are applied to a differential amplifier 3. Thus an output Vout free from the dark time output signal is obtained from a gate circuit 4 which is controlled by the generator 5.