Web inspection system having enhanced video signal preprocessing

摘要

A web inspection system that inspects a moving web for defects has an enhanced video signal preprocessing capability. The enhanced video signal preprocessing is provided by a preprocessing circuit which has a maximum signal-to-noise (S/N) ratio that is no greater than an inherent maximum S/N ratio of a raw video signal as generated by a charge-coupled device CCD camera. The preprocessing circuit is preferably DC-coupled to the CCD camera to receive the raw video signal and generate an analog filtered video signal using an adaptive feedback loop that preserves a fidelity of the raw video signal in generating the filtered video signal. By improving the video signal preprocessing, the overall defect detection consistency of the web inspection system is improved.