Method of detecting flaws on surfaces

Claim 1

In a method of surface measurement of the type which utilizes advancing a surface past a source of electromagnetic radiation directing said electromagnetic radiation toward said surface, sensing radiation reflected from said surface with an electromagnetic radiation sensing means, effectively scanning at least one of said source and said radiation sensing means repeatedly through identifiable positions across said surface generally perpendicular to the direction in which said surface is advanced, to produce a series of serial scan signals, the improvement comprising: a. dividing each of said scan signals from at least two of said series of scans into at least 30 signal increments, each signal increment being identifiable as to position in the scan; b. combining signal increments from the same position of at least one other scan signal to produce at least 30 position related dynamic average signals; c. dividing a scan signal from an additional scan into at least 30 additional positions related signal increments; and d. comparing said additional increment signals with the dynamic average signal for the same position to generate a signal indicative of surface condition.