| 摘要 |
PURPOSE: To make it possible to identify a flaw highly accurately by obtaining the steepness of the intensity of the reflected light, which is split before its transmission through a space mask, and thereby removing a falseus detection to be caused by wet attachment. CONSTITUTION: Laser light 12 from a laser light source 11 is cast on the surface of a strip 10 through a rotary mirror 13. The reflected light is condensed 14 and split into two beams through a splitter 15. One light beam is received with a photomultiplier 17 through a space mask 16 and undergoes photoelectric conversion. A differentiating circuit 18 obtains the differentiated signal from the reflected light signal. When the signal is higher than a specified threshold value, a comparator 19 sends the signal to a signal processor 23 as the flaw signal. The other reflected light, which is split 15, is received by an array-type light receiving device 21, and the reflection distribution is measured. A steepness operating circuit 22 obtains the steepness from the reflection distribution obtained in the light receiving device 21 and sends the result to the processor 23. The processor 23 removes the flaw signal caused by the remaining wet liquid based on the flaw signal from the comparator 19 and the steepness value from the circuit 22 and judges the grade and the kind of the flaw. |
