Abstract: Aiming at the low speed and match rate of the moment method and template match method, which have been used in the detection of PCB marks for a long time, and for the robustness of the image shapes, this article proposes a method that uses Freeman chain code to extract the contours of images and vertex detection algorithm to simplify the vertexes of the contours. Finally the pair-wise geometrical histograms whose rotation invariance is applied in the detection and match of PCB mark are generated by these vertexes. The experimental results using this method indicate that the comprehensive correct match rate is up to 96%.

Key words: Freeman chain code, pair-wise geometrical histogram, rotation invariance, simplification of vertexes