摘要 |
The degree of graininess or grainy edges of a traveling web may be discriminated utilizing the present invention which relates to a method and apparatus for generating a topographic signal by sensing scattered light from instantaneously illuminated areas of less than 1 mm in diameter on the surface of the web, processing at least a significant amount of said signal representative of topographic features of the web of selected lengths in the direction of travel of said web of at least 1.5 mm to determine the amount of such features of said selected length, said selected lengths contributing significantly to the graininess of the web, and thereby providing an indication of the graininess of said web.
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