PURPOSE:To control always stable storage time by detecting the sum of electric charges produced and stored by a photoelectric converting cell at each block and controlling the storage time of the photoelectric converting cell depending on the sum of the charge. CONSTITUTION:The electric charge stored in each photoelectric converting cell PSij is detected at each block by floating gates 3a-3d, outputs f1-f4 are amplified (7a-7d), and outputs g1-g4 are fed to one input terminal of comparators 9a-9d as a mean value of electric charges in each block or the sum of weighted charges between blocks. A set voltage Vrc is fed to the other terminal and its output is transmitted to a control circuit 11. When a trigger signaf T is inputted from an external device, the circuit 11 outputs a signal O representing the reading and outputs transfer clocks phi1, phi2 of an analog shift register 1. Then the register 1 transfers the electric charge signal to a charge detector 6 according to the clocks phi1, phi2 and reads an output VOS from a detector 6.
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