| 摘要 |
PURPOSE:To enable the stable detection of a flaw by providing a comparing means which resets an integrating circuit when a difference signal between an image pickup signal and a standard signal is smaller than a prescribed threshold value, and a determining circuit which detects the flaw of a substance to be inspected from an output signal of the integrating circuit. CONSTITUTION:An image pickup signal e1 outputted from a camera 1 is amplified 2 and supplied to a difference circuit 4. Meanwhile, a standard signal e2 is supplied from a standard signal generator 3 to the circuit 4, and a difference signal e3 between the signals e1 and e2 is outputted from the circuit 4. The signal e3 is accumulated in an integrating circuit 5 and simultaneously compared 6A with a threshold value K set beforehand, and when the signal e3 turns smaller than the threshold value K, a reset signal for resetting the circuit 5 is outputted. Accordingly, the circuit 5 executes integration from a time point of the signal e3 exceeding the threshold value K to its return to the threshold value K and discharges an accumulated charge according to the reset signal from the comparing circuit 6A at a time point whereat the signal e3 turns equal to the threshold value K. Therefore an output signal e4 is obtained from the circuit 5. This signal e4 is supplied to a determining circuit 7, a plurality of threshold values and the signal e4 are compared and the presence or absence of a flaw and the size of the flaw are determined therein. |
