| 摘要 |
PURPOSE:To suppress fluctuation of output of a photo-electric converter due to temperature by impressing video signals from the photo-electric converter and a signal obtained by adding DC level to a reference element output signal in the video signals to + and - input terminals of a differential amplifier respectively. CONSTITUTION:A CCD line sensor 11 is driven by clock pulse from a clock generating circuit 12, and impresses photo-electric converted video signals to the non-inversion input terminal of a differential amplifier 13. An output signal of black reference element in video signals from the sensor 11 is held in a sample hold circuit 14 by the clock from the circuit 12, and output of the circuit 14 is inputted to the non-inversion input terminal of a differential amplifier 17. DC level from a variable DC level circuit 18 is impressed to the inversion input terminal of the amplifier 17 and an output signal of an integrator 20 consisting of the amplifier 17 and a condenser 19 is impressed to the inversion input terminal of the amplifier 13. Thus, output basing on output in dark time is obtained, and sure and stable video signals free from drift due to temperature etc. can be obtained.
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