Study On The Technology Of The Plane Absolute Displacement Measuring Based On Corner Feature

CMM is the main general-purpose equipment used to measure the contour of the work piece, size of the shape and the position. Because of its complex structure, large system, expensive price, its applications is constrained. Therefore people develop a new type of CMM based on a virtual coordinate measuring machine. Virtual coordinate measurement is set up in the technology of processing digital image.It breaks through the traditional measuring method, and simplifies the traditional main body of measuring machine, and implements the three-dimensional of displacement-measuring. The matter of CMM is to have displacement information of the probe or work piece, so the displacement measurement is key technology of a new virtual coordinate measuring machine.The paper goes into the research of the technology of the pine absolute displacement measuring based on corner feature,which includes the demarcating of mearing systerm,displacement mearing and the experimentation of plane absolute displacement mearing.The calibration of mearing systerm is not only very important but also the basic of plane absolute displacement mearing. It has two aspects:the calibration of camera and workbench. In order to get the coefficient of aberrance of camera, the article adopt the two-steps to complete the calibration. And then the paper get the coefficient through the experiment and the pixel coefficient. In order to get the right position of real time images, the paper choose the calibration of workbench. The system gets the corner points by extraction arithmetic from images which got by CCD camera. Then datas of corner points is deposited. In corner points extraction, the paper introduces four extraction arithmetic and analyses them through experiments. Finally, the paper agree with the harris corner points extraction arithmetic.The measurement of displacement is very impornt and final purpose in the paper. The method based on gray vector matching which is based on corner points and around is proposed. And then it completes the orientation of real time images by the search of delamination. Finally,the displacement is got by formula.And then, it validates the feasibility by detailed experiment with the new measurement method which the paper advances. In the course of experiment,the dark oriention by the meathod based on gray vector matching is validated. Then the expriment of plane absolute displacement mearing is carried out. From the datas of experiment, a new arithmetic which is better than the old arithmetic in points extraction is proposed and the new arithmetic improves one pixel in precision than the old.Obtained in this paper, proposed absolute displacement measurement method based on gray vector matching has the feasibility of generic, practical significance. The measurement theory and methods enrich the theory and method of the field of digital image,and has provided useful reference for the follow-up study.