| 摘要 |
PURPOSE:To remarkably reduce the effect of a nonlinear distortion of an I-L curve, by clamping the tip of a horizontal synchronizing signal to a certain level on the I-L curve of a photoelectric converting element even if the APL of a video signal is changed. CONSTITUTION:A video signal TV inputted to an input terminal 1 is amplified at an amplifier 3 via a coupling capacitor 2 and inputted to a clamp circuit 13. The tip of a horizontal synchronizing pulse is fixed to a certain level with the clamp circuit 13 and inputted to an operation circuit 4. A part of the output of the clamp circuit is inputted to a comparator 9 via a low pass filter 14. The error outpur of the comparator 9 is averaged with a time constant of a low pass filter 15, inputted to the operation circuit 4 and controls a bias current of a photoelectric conversion element 5. Thus, even if the I-L curve of the conversion element 5 is fluctuated or the APL is fluctuated, the tip of the horizontal synchronizing pulse is set to a current value giving a constant output power at all times. |
