Gerber Systems Corporation

Peter M Walsh

Ronald J Straayer

Scott P Snietka

James P Kohler

H Joseph Gerber

Bruce L Davidson

Dana W Seniff

A method and apparatus used with a printed circuit board (PCB) defect detection system generates a reference database image of the PCB having tolerances for each individual PCB feature, The invention is characterized by a tolerance database of at least three states in which each color is weighted and adjacent pixels are grouped into arrays or 'bins'. An error signal is generated when the sum of the pixel weights in a bin exceeds a preselected threshold.

Automatic optical inspection system having a weighted transition database

A method and apparatus used with a printed circuit board (PCB) defect detection system generates a reference database image of the PCB having tolerances for each individual PCB feature wherein a tolerance database of at least three states in which each color is weighted and adjacent pixels are grouped into arrays or 'bins'. An error signal is generated when the sum of the pixel weights in a bin exceeds a preselected threshold.

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.

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South Windsor, CT, United States of America

Peter M Walsh