Patent US 4,173,441

An inspection system for web materials, including electronic means responsive to means scanning the web for detecting a plurality of nonuniform appearance features of the web; means for discriminating these appearance features as to class to identify the significant electrical signal components thereof; means for electrically dividing the web into overlapping areas; means for counting the number of occurrences of the significant signal components over a series of scans within each of the overlapping areas; means for comparing each count with predetermined values to electrically define nonuniform appearance features according to area; and means for combining these nonuniform appearance features to recognize the occurrence of a visual defect class as it occurs within each overlapping area.