Importance

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Abstract

A device for detecting contaminant particles on a surface of a monochrome web of material of a first color imprinted with a second color different from said first color comprises a frame member with a feed roll of said web material and a takeup roll, with the web material passing from said feed roll to said takeup roll past an inspection stage between the feed roll and takeup roll. The inspection stage has a light detecting means mounted on it for collecting light transversely from the web as the web moves past the inspection stage. The light detecting means is communicated to a light analyzing means to observe variations in the collected light and the light analyzing means is communicated to a means for indicating that a variation beyond a threshold amount has been observed by the light analyzing means. In preferred embodiment, the light collected by the light detecting device is passed through a filter immediately prior to collection in said light detection device, said filter selected so that said first color is indistinguishable from said second color after passage through the filter.

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First Claim