| 摘要 |
PURPOSE:To obtain a uniform luminance even in a dark place by changing a reference potential to a polarity opposite to that of a shading waveform in a tube type video camera device. CONSTITUTION:If a signal where shading occurs is applied to a terminal 3, a transistor (TR) Q2 is made conductive for a period of a clamp pulse (CP) corresponding to a BLK period, and the signal is clamped in the clamp potential applied to an emitter. The clamp voltage is applied to a signal processing circuit 5, and a black part level is detected by a sample holding circuit 15 and is compared with a potential VCL from a reference potential generating circuit 16, and a voltage corresponding to the difference is applied as the clamp voltage to the emitter of the TR for clamp. By this circuit constitution, the black level of an amplifying circuit 14 is stabilized. A correcting signal is superposed to a reference DC potential to change the black level clamp voltage, thus correcting shading in the dark part. |
