Agfa Gevaert Nv

Walter P Van Beeck

Jean Burtin

Maurits Geens

Alfons J Dictus

Roger J Simons

Subtle streaklike defects are detected in running webs and sheets by transversely scanning distinct lateral sections of the webs or sheets by means of lines of radiant energy extending parallel with the direction of movement of the webs or sheets. Transmitted or reflected radiation is received on corresponding photocells that move synchronously with the lines of radiant energy. During each scan of each section of the webs or sheets, a large number of comparisons occur between the output signals of each photocell at a given first lateral position and at a second lateral position that is separated from the first one by a distance that is of the order of magnitude of the width and preferably half the width, of a streaklike defect to be identified.

Method and device for inspecting a moving sheet material for streaklike

Device and method for the optical inspection of speck-like and streaklike defects in a moving web. A source of radiation illuminates a transverse zone of the web, a series of photocells measures the radiation after transmission through, or reflection from the web, and a grating arrangement modulates the radiation received by the photocells, thereby to modulate the output signal of each cell by an A.C. component.

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Sinaai, Belgium

Walter P Van Beeck