Apparatus for web defect detection including a web swatch that contains a defect

摘要

An improved web scanning inspection system that includes a fixed standard web swatch containing representative objectionable defects in the path of the scan beam at the onset of each scan in order to calibrate inspection system discriminator thresholds. Gating and logic circuits are arranged to extract amplitude and duration characteristics of the defect related portions of the signals generated by scans across the standard swatch material. These are then used to actuate an alarm whenever the inspection system discriminator circuits fail to detect the objectional defects in the standard web swatch.