| 摘要 |
PROBLEM TO BE SOLVED: To detect not only spot marks on a surface to be inspected but also an extremely wide and narrow line mark extended in the peripheral direction and width direction, by devising the irradiation direction of the surface to be inspected. SOLUTION: A metal ring defect detector comprises light sources 31, 41 for irradiating the surface to be inspected of an inspection target 2 traveling in a fixed direction with light; a first waveguide 32 for guiding reflection light from the surface to be inspected to a first light receiving element 33 and a second waveguide 42 for guiding the reflection light to a second light receiving element 43; a differential value computing means for calculating the differential value between an electric signal output from the first light receiving element or an electric signal correlated to the electric signal, and an electric signal output from the second light receiving element or the electric signal related to the electric signal; and a discrimination means for discriminating the presence and absence of defects on the surface to be inspected by comparing the differential value with a prescribed threshold. Light from the light sources 31, 41 is applied in the traveling direction of the inspection target at approximately 45°crossing angles (ϕc,ϕd). COPYRIGHT: (C)2006,JPO&NCIPI
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