PURPOSE: To eliminate temperature spots and the influence of a scale in the defect discrimination of a high-temperature tested aterial, by generating the material surface temperature level, where no scale exists, as a reference signal and discriminating defect signals on a basis of the difference between the reference signals and video signals.
CONSTITUTION: Video signal acquired from high-temperature tested material 1 by image pick-up unit 2 are not only sent to storage circuit 4 for a fixed time delay but also sent to peak hold circuits 6 and 8 which define the peak for every picture dividing pulse to divide video signals in the scanning direction as the signal of the picture element, and the average value of peak signals of plural picture elements is outputted successively for every picture element, and the average value is compared with the delay signal from storage circuit 4 as a reference signal, and the difference between them is obtained by subtraction circuit 15, and the difference signal is sent to hurt decision circuit 16.
NISHIMOTO YOSHIROU
KIMURA NOBUO
