| 摘要 |
PURPOSE:To obtain the binary pulse with fidelity of original signal, without being subject to the effect of black level changed in the temperature change, by picking up the substantial signal through the subtraction of background level from the video signal output from the photoelectric conversion unit. CONSTITUTION:After amplifying the video signal (a) from the photoelectric conversion unit fed to the input terminal 11 at the amplifier 12, it is fed to one terminal of the differential amplifier 13 and the sample hold circuit 14. The output level of the amplifier 12 is held at the circuit 14 in synchronizing with the output pulse (b) of the sample hold control circuit 15, the level (c) held is input to another terminal of the amplifier 13 to obtain the difference with the output signal of the amplifier 12 and the difference is fed to the differential amplifier 17. Further, the background level is subtracted from the signal (a) with the amplifier 13, the difference with the potential of the DC power supply 18 is obtained at the amplifier 17 and the substantial signal (d) is output to the output of the amplifier 17. This signal is fed to the integration element circuit 26 and the adder 23, the outputs of the circuit 26 and adder 23 are fed to the comparator 24, to obtain binary pulse of signal (a) with fidelity. |
