| 摘要 |
PURPOSE:To stabilize the black level of a picture image, by detecting a black peak value of an image signal immediately before impressing to a CRT and by regenerating the back level in DC. CONSTITUTION:A signal processing section 4 switches corresponding to a blanking pulse PB input from a control terminal and putputs a constant-voltage B1 while blanking, and in the other period, outputs an image signal S. This output is fed to a peak clamp circuit 7 through a contrast amplifier 6 then, is output to terminal 10 through a driving circuit 9. If the value of constant-voltage B1 is set to the specified value between a white peak value level and a pedestal level, the lowest output signal of the signal treatment section 4 becomes voltage B1 in case no level lower than the voltage B1 exists in the image signal S. As this lowest level is output keeping, the voltage B2 of the peak clamp circuit 7 the black level is held to a constant value. |
