| 摘要 |
PURPOSE:To avoid the deterioration of video quality and the production of alarm of deficient light amount when a video signal is at a specified level, by providing an automatic iris control circuit, automatic gain control circuit and light amount deficient alarm circuit. CONSTITUTION:An iris position signal obtained from an automatic iris control section 10 is picked up via an iris open detection section 20 and an automatic gain control potential control section 21, this is applied to an automatic gain controlling detecting section 14 to control the automatic gain control potential, and the controlled potential is applied to an automatic gain control section 6. Further, the control section 6 is operated before the iris blade 2 opend with an automatic iris control circuit 15 to prevent the deteriorated video quality. Further, when the iris blade 2 opens, a comparator 16 compares if the automatic gain control potential is greater or smaller than the prescribed level, allowing to display for suitable light amount alarm for a TV camera. Thus, when the video signal is at the specified level, no alarm of deficient light amount can be made. |
