Inspection tool

Abstract

This patent discloses an improved inspection tool for rapidly inspecting miniature electronic conductor patterns, circuits and the like. The tool focuses a laser beam to a small laser spot that raster scans a large conductor pattern area on the workpiece being inspected. Reflected laser light from the workpiece impinges upon a light detector that generates electrical signals according to the presence or absence of conductor pattern material on the workpiece at the momentary X and Y coordinate of the scanning laser spot. The light detector signals are compared with a previously encoded data image of the correct circuit pattern for the X and Y coordinates of the scanning laser spot. When the signals and the data agree at all X and Y coordinate points the workpiece is accepted. If the signals and the data do not agree at one or more X and Y coordinate points a defect in the circuit pattern is indicated. A defect may indicate out-of-tolerance dimensions, possible electrical short circuits, and/or open circuits. The extent of a defect may be determined by adjacent X and Y coordinate points and suitable computer programming, while workpieces having extended or out-of-tolerance defects are rejected. The improved disclosed inspection tool includes apparatus for automatically compensating for variations in the workpieces, and to effect registration for the scanning laser spot.