High-precision Vision Measurement System

The vision measurement technique based on the computer vision, as it has the features of non-contact, real-time and on-line measurement and high accuracy, has been developed fast and used widely. The thesis makes a thorough researches and studies of the stereo vision measurement technique which is applied for the measurement of the structural parameters of a comb cutting tool. Accuracy is the most important index for the measurement. In order to get an accurate measurement, the thesis dwells on the reasons and types of distortion of imaging system and has built up an imaging model considering the influence of lineal distortion and non-lineal distortion of lens, which lays a foundation of accurate measurement. After building the imaging model, the thesis then makes an approach of the three key techniques: the calibration of imaging system, stereo matching and the sub-pixel edge detection based on the fact that the measurement of structural parameters ends in the operation of the coordinates of special coordinates. The imaging system calibration is mainly used to calibrate the non-lineal distortion coefficients of system. The thesis builds up a high-accuracy calibrating model including the radial distortion and the tangent distortion of lens, which is solved by the method that the non-lineal coefficients are obtained by the iteration after the calibrating model is firstly solved without considering the distortion of imaging system, and gets a high-accuracy calibrating. Stereo matching is difficult to deal with in the stereo vision. The thesis gets a higher matching accuracy with the help of the related method in district improved by the least square method. The edge detection is important in image processing. This thesis puts forward a new sub-pixel measuring method, which confirms the approximate position of edge by conventional template arithmetic, and then gets the precise position of edge by curve fitting. This method can obtain sub-pixel locating precision without the sacrifice of the needed speed by the coarse and precise location. Finally, the thesis also illustrates the practical application taking the measurement of structural parameters of comb cutting tool. Because the...