| 摘要 |
PURPOSE:To detect pinholes accurately free from effect of disturbed light such as leakage light, by providing a projector section on one side of material to be detected while two photo detectors are on the other side thereof at a specified interval to compare the time difference of the detection signal with a reference time. CONSTITUTION:A projector section 2 is provided on one side of material 1 to be detected running continuously while two photo detectors 3 and 4 are provided on the other side thereof 1 at a specified interval in the direction of the material 1 being detected runs. Then, output signals of the detectors 3 and 4 are inputted into waveform shaping circuits 13 and 14 via amplification circuits 7 and 8, differentiation circuits 9 and 10 and level detection circuits 11 and 12. The signal from the photo detector 3 is inputted into a shift register 15 and then, into a comparator circuit 17 by a signal from a reference time generation circuit 16 after a reference time passes. On the other hand, a signal from the photo detector 4 is inputted into a comparator circuit 17 immediately after the shaping of the waveform. A pinhole signal Sp is outputted from the circuit 17 when the time difference is zero or within an allowable range by comparing both the signals. |
