Method and apparatus for inspecting web surface

摘要

Method and apparatus for inspecting a surface having a photosensitive layer on a wide film web from which lateral margins are slit away, by detecting defects of the photosensitive layer of the surfaces of the lateral margins. The intensity of a line of light which is projected onto a lateral margin of the web is modulated by the surface of the lateral margin and received by reflection by a line sensor for producing an analog video signal which in turn is converted into two binary signals of high and low output levels. From the combination of the two binary signals, the presence of a defect is detected, because the intensity of the modulated reflected light will vary from a value characteristic of the absence of a defect.