| 摘要 |
PURPOSE:To obtain picture with high fidelity for reproduction, by detecting the area of dark part of screen and by the selection of amplitude limit system when the area of dark part is more than the specified value and of the black level control system when less than specified value. CONSTITUTION:The video signal is fed to the video amplifier circuit 3 and the dart part area detection circuit 7. The amplification factor of the circuit 3 can be controlled by the DC bias, and it is connected to the pedestal clamp circuit 4, and the output of the circuit 3 is clamped to the reference potential for DC regeneration. The output signal of the circuit 4 is amplified at the video output amplifier circuit 5 and output to the receiving tube 11. The beam current detection circuit 9 is connected to the high voltage generation circuit 10 and the detection signal is output after it is ON when the beam current is more than the limit value. The output of the circuit 9 is connected to the control circuit 8. The dark part are detection circuit 7 detects the dark part of video signal for integration to output the area detection signal. The circuit 7 is connected to the circuit 8, which controls the black level bias voltage of the circuit 4 and the amplification factor of the circuit 3. |
