| 摘要 |
PURPOSE:To detect distinctively a foreign matter sticking on the surface of a material to be inspected and a flaw and an internal defect by making light incident on the material to be inspected and reflecting it totally therein. CONSTITUTION:An irradiating device is provided beside a sheet 1 and a line scanner 3 is provided above it so that the scanning direction is perpendicular to the moving direction of the sheet 1. Then, light Li from the irradiating device enters the sheet 1 at an angle theta of incidence as shown in a figure A. Light Lp propagated in it is refracted at an angle theta1 to travel while reflected repeatedly without leaking out of the sheet 1, so that transmitted light Lo is outputted from a flank 1b eventually. Then, if there is a flaw 7 in a flank 1c as shown in figure B, light Lp is incident on the surface of the flaw 7 at an angle theta4 and transmitted at an angle theta5, so the transmitted light Lo is detected by some of elements of the scanner 3. A video signal obtained by the scanner 3 is applied to a signal processing circuit and if there is a defect, that is outputted to an alarm 9. |
