The 3-D Profile Measurement Of Step Shape Complex Structure Based On Linear Structure Light

Up to now, the optical 3D shape measurement technology has experienced rapid development. However there are still difficult problems to be solved, such as a low accuracy, too simple profiles to be measured, view blind areas in the monocular vision system. The existing measuring methods are not capable of measuring not complicated contour surfaces. In view of the above problems, this thesis puts forward a method to measure the contour of a complex surface based on the line structured light 3D measurement method.Complex shapes cover a wide range of irregular contour. Besides of flat surface, regular cambered surface, smooth edge angle or some inerratic shape, there are terraces, wedge or complex profile parts in some cases. There will be unpredictable image pattern when a linear laser beam irradiates on those complex contours. For example, the light plane will be divided into two parts if it is parallel to the terrace shape, images obtained at this time will not be able to restore the true appearance of the steps. Therefore, in the study of complex 3D contour measurement, the usual way of the image analysis cannot meet the measurement and reconstruction. It is necessary to find other solutions and image processing algorithms.In this thesis, it completes to design a hardware of the measurement system and a software based on the structures of a complex structure. First of all, the thesis analyzes the principle of the line structured light method of complex contour depth information acquisition technology, and researches on the camera calibration technology. Secondly, research on key technology of contour measurement principle such as the pre-processing of light band, the algorithm of getting the contour data, is performed. After introduction mature image preprocessing algorithm in our laboratory, the thesis describes algorithms in the software to process a light band. Several commonly used methods of extracting the light stripe center are discussed and a Zhang fast parallel thinning algorithm for fast thinning method is proposed. The join algorithm based on NURBS curve to face the problem of the binocular vision system in improving the measurement accuracy of the system. The diagnosis and treatment of some special types of contour is studied. For step shaped outline, the laser line width is unable to achieve ideal infinitely narrow band, the line plane will be divided into two parts. In order to solve this problem, a method of stepped cross section contour reduction is put forward. Finally, through the building system and programming software, the working process and principle of the complex contour measurement system is described. The experiment results are analyzed and summarized.