The Realization Of The Tiny Parts Image Parameter Measurement

The measurement of round holes and their positioning relation on small parts is a difficult problem for normal contact measurement. However, this problem can be easily solved by the image measurement without touch. The key of this technology includes image acquisition, edge detection, and round detection, etc. The performance evaluation indexes for this technology are the precision and speed of measurement. Using high resolution image acquisition equipment is the direct mean to ensure the accuracy of measurement. But at the same time, it brings large image data scale, and slows processing speed;an intuitive example is that edge detection speed is approximately proportional to the image size. In order to deal with the problem of slow speed of the large size image edge detection, this article uses two steps edge detection strategy based on sampling to promote detection speed. Random Hough transform is the most important and the most convenient testing technology for rounds, this article uses double radius-error to calculate roundness and record edge points of rounds.The core content of this paper as follows:(1) Edge detection technology. After the acquisition of high resolution image, edge detection is the first step of measurement, results of which have an important influence on measuring speed and precision of subsequent steps. This paper introduced the principle and method of canny edge detection and sub-pixels edge detection. When using canny edge detection, even, there is the problem of low detection speed itself; to solve the problem, two step edge detection strategy based on sampling is used.(2) Round testing technology. Hough transform is important round recognition algorithms. Firstly, this paper analyses and compares the basic theory, then, sums up exited practical improving method, and at last uses double radius-error to calculate roundness and record edge points of rounds for the problem of single radius-error.(3) Measuring software design. when realizing measuring the target parts, target parts is divided to small areas using inner circle centre as reference point, in order to improve probability of the single random pick on the same round edge;Finally, realized measuring software with the C#programming language, and debug it, and analyzed the main factors affecting the performance,and approximately adjusted the radial distortion of used lens to reduce the measurement error.