| 摘要 |
PURPOSE:To prevent picture quality degradation by holding the level of the modulated video signal from a camera head fixed by a variable gain control amplifier. CONSTITUTION:The modulated signal which includes the synchronizing signal and is dependent upon the video signal with the modulation degree of the black level part fixed is generated from camera head 1 and is transmitted to camera controller 2 through cable 3. In controller 2, this modulated signal is led into variable gain control amplifier 10, and the synchronizing signal is extracted through detector 11 from the output. This synchronizing signal is controlled by automatic phase control synchronizing circuit 16. This synchronizing signal is supplied to gate signal generating circuit 17 to generate a gate pulse corresponding to the black level part of the video output. The detection output is gated by this pulse, and amplifier 10 is controlled by the output. Thus, the level of the modulated video signal is held fixed, so that degradation of the picture quality can be prevented. |
