Vision detection of unthreaded hex bolts
Zhifeng Zhou · Optical Technique · 2012
In order to measuring the external dimensions of unthreaded hex bolts,a vision measurement method based on image detection is proposed.First,the manufacture process of hex bolts is briefly introduced,and the importance of measuring unthreaded hex bolts is pointed out.Second,the principles of Hough transform are analyzed,and a circle detection method is introduced.A method of detecting regular hexagon is presented.According to having been detected lines,the equations of lines are constructed in image space,and the coordinates of intersection points of adjacent two lines are computed.The distances between adjacent intersection points and the angles between adjacent lines are calculated.Then the circle detection method based Hough transform is employed to inspect whether all intersection points locate at the same circumference.Finally,the detecting experiments are used to illustrate the performance of the proposed method.The measurement errors of bolt's diameter,angles between adjacent two edges of regular hexagon of bolt's head and lengths of edges of regular hexagon are 0.37%,0.40% and 1.25% respectively.The result demonstrats that the presented method is effective and can precisely detect the external dimensions of unthreaded hex bolt.