| 摘要 |
PURPOSE:To realize the correction of dark current with high accuracy by a very simple circuit, by using a horizontal driving signal controlled in response to a dark current value. CONSTITUTION:An image pickup tube consists of a main body, a deflection coil, a focusing coil and a photoconductor and the like and a dark current correcting circuit is connected to the focusing coil. A stabilizing circuit section having a transistor (TR)1, operational amplifier 9, and a resistor R1 stabilizes the current level of the focusing coil to a constant value. The change in the DC resistance of the focusing coil causes a potential change of ground side and an operational amplifier 11 compares this potential with a reference potential. The output of the operational amplifier 11 is squared with an output of a multiplier 12 and inputted to a differential amplifier 13. The differential amplifier 13 controls the amplitude of a horizontal driving signal HD with an output of the multiplier 12. The differential amplifier 14 subtracts the output signal of the amplifier 13 with the output signal from the image pickup tube and this output is inputted to a process amplifier processing the video signal. |
