A Study Of Spatial Filtering And Image Processing In Measuring System With Laser Beam Irradiation

In the industry, cylinder parts are widely used, improving the centerline position and the diameter measurement accuracy of cylinder parts is an important problem in the field of manufacture. And it has been the goal, which the craftsman and the engineer eager after from beginning to end, to find the better way of centerline position and diameter measurement and to make these measurements more and more precise. In this paper, we bring forward a vision inspection by use of optoelectronic technology, sensor technology and image processing. The method takes use of high resolution CCD to obtain image. And the image acquisition, image processing and calculate are all resolved by computer. We can measure the cylinder parts'centerline position and diameter availably and quickly. And a new method used to improve the measurement accuracy of slender column's edge by the measuring system with laser beam irradiation is proposed in the paper. By placing a pinhole at the focus center of the convex lens, the high frequency band of the Fresnel straight edge diffraction that caused by a column's straight edges can be eliminated. Its feasibility is analyzed in theory and experiment is done to verify theoretically conclusions. The dissertation focuses on the key theory, method and techniques of improving the cylinder diameter measurement accuracy. The main research concerns on the following lists: (1) Compared with existing devices and principles of the cylinder diameter measurement, a new Measuring System With Laser Beam Irradiation is proposed. And in order to eliminate the stripes of the Fresnel straight edge diffraction caused by a cylinder's straight edges, we bring forward a new way to eliminate the high frequency band of the diffraction by placing a pinhole at the focus center of the convex lens. By this means the accuracy of the edge measurement has been improved. (2) By analyzing the theory of the Fresnel straight edge diffraction and Spatial Filtering technology, it proved that the way to eliminate the stripes of the Fresnel straight edge diffraction by low pass filtering is feasible and experiment was done to verify theory conclusions. (3) The scheme of hardware system and the software system of the image processing is designed and the image processing techniques involved in the research are discussed and studied in the thesis, and their specific applications to the research are decided. (4) Put the image processing steps into execution by use of the Image Processing Toolbox of Matlab and decide the way to obtain the centerline and the diameter of the cylinder and experiment was done to verify theory conclusions.