Method and apparatus for performing fixturing in a machine vision system

This invention relates to machine vision systems for object location and inspection and, more particularly, to techniques for fixturing targets. A single non-rotationally symmetric fiducial mark, such as a Universal Alignment Target, is placed on an object and the alignment of the object is determined with a vision tool that can align objects with translation and at least one additional degree of freedom, such as angular orientation. Alternatively, if a unique non-rotationally symmetric feature occurs naturally on the object, that feature may be used instead of a fiducial mark. In one embodiment, a geometrical feature matching vision tool is used to locate the single fiducial mark. In another embodiment, a normalized correlation search tool is used to locate the mark. The tool internally generates a set of rotated and scaled patterns that are then stored. The stored patterns are subsequently used to perform the search. In still another embodiment, a normalized correlation search tool internally generates a set of rotated and scaled patterns at runtime when the search for the mark is being performed.