Method and device for testing transparent sheets

Abstract

Method and device for inspecting transparent webs for the presence of defects which include scanning the web to be tested with a flying spot, directing the light passing through the web to a receiver system which has transparent and opaque regions, supplying pulses by a photoelectric transducer disposed in the receiver to a computer corresponding to the light intensity received at the receiver system, directing the light spot such that when the material web is free of defects the light spot covers the opaque and the transparent regions of the receiver system in a continuous alternation, supplying the light spot intensity changes representing the change of regions to the computer as pulses and the light intensity fluctuations based on defects to the computer as pulses, and in the computer evaluating these pulses while these pulses are separated according to the regions of the receiver system.

Dependencies are inferred from the claim text.