| 摘要 |
PURPOSE:To obtain a stable picture quality, by irradiating a constant light to a set part of a image pickup tube, extracting a carrier signal and controlling a beam current so as to make the carrier signal constant at all times. CONSTITUTION:An output signal of the pickup tube 5 is amplified at a preamplifier 6. From this amplified signal, a carrier signal of an overscanning detecting region is detected at a sampling circuit 7 with a gate pulse formed at a gate signal generator 12. The detected signal is rectified into a DC at a rectifier circuit 8 and DC-amplification is done at a DC amplifier 9. This DC- amplified signal is mixed with a reference signal at a mixing circuit 10 and impressed to a control electrode G1 of the image pickup tube 5 used for the control to flow a constant beam current. |
