Abstract
An important inspection task in the automated assembly of printed circuit boards (PCBs) is that of detecting if all components have been placed correctly on the board. This paper describes a constrained evolutionary search based inspection technique for simultaneously detecting multiple component objects in a source image. The approach has the advantage that it does not rely on image alignment (registration) as do conventional optical inspection methods such as image subtraction. It is a template based search method which achieves speed and quality requirements by making use of an evolutionary algorithm and a simultaneous search for multiple objects in a source image using a generalised template. The generalised template matching method defines a template model that takes into account the statistical variations between the grey-level appearances of components. The evolutionary search for specific components is constrained to Canny edges making this a fast method for locating multiple targets. Results are presented for locating multiple surface mount resistors on a PCB so that missing components can be reported.