The Image Measurement Of Axisymmetric Objects' Geometrical Dimensions

With the continuous development of measuring technology, it's higher and higher that the requirements of accuracy and rapidity in modern industry to objects'dimensional detection. As a non-contact measuring tool, image measuring art has many merits such as high-accuracy, high-speed, high-efficiency and high automatic degree. Therefore it satisfies the demands of the industrial testing field very well and applies widely in producting and processing. From the start of measuring question of axisymmetric objects'geometrical dimensions, the paper is committed to building the image measuring system which is suitable for engineering application.Firstly, it describes the relevant theories of the image measuring technique, and explains its current situation and developing trend. According to the the testing requirements of actual engineering, it is designed that the cylinders'dimensional measuring system including hardware and software systems based on the measuring principles of cylinders'parameters. And it raises the measuring programs of cylinders'height, top diameters and roundness error, diameters and thickness of the base.Secondly, it analyzes the components of hardware system, which is composed of the illuminational systems and the systems of image sensors. And it discusses the selections of every part in hardware systems.Furthermore, according to requirements of the project, the paper studies the camera calibration and image processing algorithms of software system. On the basis of Tsai calibration, it puts forward a kind of method for planar calibrating, which is joined the calibrations of principal point coordinate and aspect ratio. In addition, it is introduced that the intermediate variable, which greatly reduces the computational complexity and improves running-speed on the analysis of least square method for roundness error assessing.Finally, we take cylinders of three models as detecting objects, and use the measuring system to measure their geometric dimensions actually, then complete the detectional experiments of parameters, also carry out analyses on measuring errors. The experimental results show that the system can meet the requirements of accuracy, so it can be used for engineering testing.