| 摘要 |
PROBLEM TO BE SOLVED: To make a black level stable when photographing an object with high sensitivity by controlling the charge storage time. SOLUTION: The output signal of a charge coupled device CCD image pickup element 1 is fed to a sample-and-hold circuit 2, where the signal is converted into a continuous signal, which is fed to a black level clamp circuit 3. The black level clamp circuit 3 decides the reference black level, based on the signal from the sample-and-hold circuit 2 and a black level clamp pulse (clamp pulse A or B) from a pulse changeover device 7, a video signal processing circuit 4 applies gain control and gamma processing or the like to the signal and provides the output of a video signal. A synchronizing signal generating circuit 5 generates the clamp pulses A, B and gives them to the black level clamp circuit 3 via the pulse changeover device 7. A control circuit 6 conducts on/off control for gamma processing and controls the pulse changeover device 7 and the like.
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