Research On The Key Technologies Of Parts Geometrical Size Measurement System Based On Image

With the development of advanced manufacturing technology, the traditional measurement technique and measurement range will not satisfy the requirements of modern machinery manufacturing technology gradually. More and more attention of the part's geometry and tolerance measurement method based on image has been caused. The part's geometry and tolerance measurement method based on image has the advantages of non-contact, being able to measure the sizes of special part such as easy to deform, small size, the width of narrow gap and droplet's diameter etc., which is hard to do by traditional measurement methods and has the advantages in the aspects of efficiency and convenience of measurement, so the measurement method based on image has a wide range of applications.On the hardware configuration, this paper focuses on the digital cameras and lighting systems which affect the ultimate measurement accuracy. Based on the need of enterprise and actual project, the author researched in theories and algorithms of image processing and measurement such as conversion of image types, denoising, image's binarization, edge detection etc. By doing experiments to compare the effectiveness of various algorithms, the author proposed the appropriate image processing methods and separated the function of the whole measurement system into several modulars. During the process of image processing, in order to improve the measurement accuracy and guarantee measurement speed, based on the theory of image's gray distribution and theory of image sampling, on the basis of using traditional template operators to determine the location of the edge, combined with inhibition technology of local non-max value to eliminate false border points, and using Gaussian curve interpolation along the point's gradient direction, the location of boundary points were positioned at the level of sub-pixel. The edge features were fitted with the method of Least-squares with the extracted border points, and the size or tolerance was measured according to the theories and standards.Based on the above study, with the support of the military projects and the business needs, an image-based geometry and tolerance measurement system was developed. Not only conventional part's two-dimensional geometry and tolerance measurement can be achieved by the software system, but also the macro-micro feed double control system can be integrated with it, which achieved the closed-loop control of thin wall part's position. A test of accuracy on the measuring system is done, and the result of measurement of the precision blocks shows that the system has reached a level of micron accuracy. By measuring the width of chip's pin in the industry of microelectronics as the adaptability measurement of the system, the result confirmed that the software system has practical value and general usage.