| 摘要 |
PURPOSE:To improve the accuracy of exposure control when incident light intensity is high by forming a control pulse with a driving pulse in the blanking period of a horizontal synchronizing signal when the incident light intensity is low and by generating a pulse for driving in the effective period of the horizontal synchronizing signal in an area in a vertical scanning direction when it is high. CONSTITUTION:A masking signal to mask the outer peripheral part of a screen is formed in a masking circuit 27. In a state in which the tip 5 of an electronic endoscope is not approaching an object to be observed, an AND condition with a switching signal is not satisfied in an AND circuit 22, therefore, only a mixer 16 is operated, and the pulse for driving from a timing generator 18 is mixed with an exposure control signal from a PWM signal generation circuit 15, and a discharge pulse is supplied to a CCD 10. When the tip of the electronic endoscope approaches the object to be observed, the AND condition is satisfied in the AND circuit 22, and a mixer 23 is operated, and the pulse for driving formed in the effective period of one horizontal synchronizing signal is outputted to the mixer 16.
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