Abstract: A system for detecting flaws in printed circuit boards. The circuit board is scanned by a video camera to provide a serial stream of bits each indicative of a picture element within a particular scan line. The serial stream of bits is formulated into binary numbers each representative of a contiguous path of picture elements composed of n.times.n picture elements. Each of these binary numbers are compared with a corresponding one of a set binary numbers stored in memory representative of a perfect master printed circuit board. Failure of the printed circuit board to match the stored master indicates a flaw. The invention also includes means to generate overlapping patches to insure detection of defects which occur in adjacent patches.