| 摘要 |
PURPOSE:To enable to obtain the best quality of a picture at all times, by changing an iris of lens within a range of iris where the performance of a lens is excellent and changing the gain of amplifier at other ranges. CONSTITUTION:Video signals R, G, B are fed to a level detector 10 to detect the peak level. The detected output from the detector 10 and the control signal from the iris servo remote control 11 are added at the adder 12. In the iris control, the output of the adder 12 is input to comparators 13, 14, and compared with the upper and lower limit set values, and the output is fed to the sample hold circuit 16 via the NAND circuit 15 to control the operation of the circuit 16 to receive the output of the adder 12. On the other hand, the output of the adder 12 is fed to one input terminal of the differential amplifier 17 and the output of the circuit 16 is fed to another input terminal. Further, when the circuit feeds the input as it is to the output side, the sample hold circuit 18 keeps the video gain control voltage to a constant value. Thus, the output of the circuit 18 is changed according to the output of the adder 12 in other range. |
