| 摘要 |
PURPOSE:To discriminate a nondefective and a defective through-hole definitely by providing the 1st binary coding circuit which codes a video signal generated by only light leaked in a mask into a binary signal and the 2nd binary coding circuit which codes a signal generated by both the light leaked in the mask and light leaked in a defective. CONSTITUTION:The video signal S1 is coded by the 1st binary coding circuit 20-1 with a high slice level V1 into the binary signal S2, which is inputted to a correlation circuit 20-3. Namely, this binary-coded signal S2 is inputted as a video signal originating from only the light leaked in the mask for the position detection of the reverse-surface side opening of a through-hole. The video signal S1, on the other hand, is coded by the 2nd binary coding circuit 20-1 on the basis of a low slice level V2 and inputted as a binary-coded signal S4 to a defective searching circuit 20-7. Consequently, it is made extremely definite to discriminate between a nondefective and a defective through-hole. |
