DEVICE FOR INSPECTING WEBS OF MATERIAL TRAVELLING AT HIGH SPEED

摘要

A web (10) of material travelling at high speed is inspected using a light source (11) which directs a light beam (4) on to a rotating reflecting wheel (5) which projects the beam, via a stationary folding mirror (1) positioned centrally above the web (10), on to the latter. The folding mirror (1) is composed of at least two reflecting surfaces (2) which form an obtuse angle ( alpha ) with each other. As the reflecting wheel (5) rotates, the light beam (4) reflected from a polygonal facet (14) of said wheel skims all reflecting surfaces (2) of the folding mirror (1) in succession. As a result, the number of scans of the web (10) per polygonal facet (14) increases with increase in the number of reflecting surfaces (2).