Abstract: Apparatus and method for illuminating circuit boards to quickly and efficiently inspect them for various imperfections. An intense light beam is directed at an oblique angle at the surface of the board to be inspected. Some of the light enters the board and is partially scattered while some of it is reflected from the opposite surface. A detector array positioned above the inspected surface is scanned over that surface and distinguishes light and dark areas. Any light opaque area such as a conductive path or pad is a dark area while portions of the board free of circuitry is interpreted as a light area by the detector. Signals from the detector may be employed for many purposes relating to the circuit pattern on the board.