SIGNAL PROCESSING METHOD FOR DETECTION OF SURFACE DEFECT FOR HIGHHTEMPERATURE TESTED OBJECT

摘要

PURPOSE:To obtain the reference pattern without being affected by defect, by comparing the video signal with the reference pattern signal at that time point, and sequentially averaging the signal immediately before the difference exceeds a given value after peak-hold. CONSTITUTION:The video signal VS catching the radiated light picture of high- temperature tested object 1 on the TV camera 2 is in A/D conversion. The converted output DS is fed to the memory circuit 5 and the circuit 7 of the peak-hole circuit 6. The circuit 7 peak-holds DS transversely and feeds the output TS to the longitudinal peak-hold circuit 8 and the comparator 9. The comparator 9 compares TS with the reference pattern signal BS, and if TSBS, the gate signal G is generated to stop the reset signal of the circuit 8. Thus, the section of longitudinal peak-hold is not renewed, and the peak-hold circuit 6 outputs the longitudinal peak-hold signal LS in which the dark part of tested object is rejected. The average calculation circuit 12 averages LS and generate the reference pattern signal.