| 摘要 |
A flaw detector, for detecting a flaw in a sheet, picks up, by means of a plurality of linear array cameras, the light of rays transmitted through a sheet. The video signals from the linear array cameras, which are appropriately processed, are used for checking whether a flaw is present or not. A sensitivity-difference correcting section corrects sensitivity differences amoung the cameras and among photosensitive elements of each camera, which sensitivity differences are contained in the video signal. Automatic gain control sections, for transparent and opaque flaws, respectively, control the sensitivities of the video signals. These signals are differentiated, and then compared with a predetermined slicing level, thereby to check whether transparent and opaque flaws are present or not.
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