Method and apparatus for distortion compensation in an automatic optical inspection system

摘要

A method and apparatus for compensating substrate distortion in automatic optical inspection (AOI) systems eliminates false error signals during printed circuit boards (PCB) defect detection. The present invention is used in feature edge transition AOI systems that employ pixel to pixel comparison between CAD and scanned PCB feature databases. The present invention divides the substrate into a plurality of regions or "tiles". A distortion vector for each tile is calculated and is used to generate a shift of pixels within each tile which removes any variation between the preferred pixel location and the actual pixel location, thereby enabling the AOI system to avoid generating error signals when features are only misplaced on the substrate.