Study on the method of defect circle hole detection in PCB microscope image
Liu Lin · Journal of Optoelectronics·laser · 2009
The basic principles of circle detection of Randomized Hough Transform(RHT) and circle fitting based on least square method(CBL) were analyzed,and their specific methods in the algorithm of circle detection were discussed.In accordance with the advantages of RHT and CBL,a new method of circle detection was presented:At first,the preprocess of PCB image was executed,and the parameters of some original possible circle were confirmed by the principle of RHT.And then,the distance was computed from every point in the edge image to each original possible circle detected by these parameters.Based on the distance,the point sets in the vicinity of each original possible circle were extracted and the disturbance or noise far from the original possible circle was deleted.At last,the exact parameters of circle were obtained after fitting the points within each sets with LSM,the last real defect circle edge was extracted by simple method of pattern clustering.The real edge of defect circle hole of PCB microscope image was obtained as far as possible when we applied the method to detect defect circle holes which include fuzzy and noise.