A fast PCB hole detection method based on geometric features

Computer vision methods have raised great interest in the manufacture of printed circuit boards (PCBs). The detection and localization of circular holes on PCBs are very important for positioning or defect detection. In this paper, a new method for such detection is presented. The proposed method first uses an adaptive edge detector to obtain the edge image. Then it utilizes the symmetry of the circle and transforms the PCB image into distance space where a Euclidean distance relationship is shown. Then a rapid circle center search (RCCS) algorithm is used to locate the center of each circle. This algorithm first scans the possible locations of each center and then filters out false selections by measuring how close the candidate center is to the contour with the Hausdorff distance. In addition, the proposed method is compared with the method based on the circular Hough transform for multiple test images in terms of speed and accuracy.