| 摘要 |
PURPOSE:To eliminate the influence of variance in the quantity of source light and variation of external light and to accurately detect a defective at any time by differentiating a video signal spatially and detecting the defective. CONSTITUTION:A defective detecting circuit 2 inputs the video signal inputted by a television camera from an input terminal 5 and then sends out a detection signal from an output terminal 6 if detecting a defective. The video signal inputted from the terminal 5 is inputted to a buffer 7 and then inputted to a clamping circuit 8. A video signal outputted by the circuit 8 is inputted to delay elements 9a-9d in order. The elements 9a-9d consists of delay lines which delay the signals and the output signal of the circuit 8 is inputted to subtracting circuits 10a-10d at the same time. For example, the circuit 10a calculates the quantity of variation between the output video signal of the circuit 8 and the current video signal. The respective quantities of variation are inputted to comparators 11a-11d, which compares their inputs with threshold values set by variable resistors 12a-12d. If the quantities of variation exceeds the threshold values, signals are outputted to an OR circuit 14 through inverters 13a-13d and the signal is sent out from the terminal 6. |
