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 i...