Research On System Of Non-Contact Tubing Thread Measuring Based On Computer Vision

This topic comes from the cooperation project between Shengli Oil Field in Dongying and Hengjitai limited company in Qingdao.Aiming at the problems in the measurement of tube thread parameters, the paper presents a non-contact measuring way which makes use of the current image measuring theory and is based on computer vision according to API definition about thread size. The key technologies in the method are discussed in the paper.The principle of this measurement system is the following. First, it makes use of CCD camera to take a thread picture, then transports the picture into the computer by PCI card, finally gets the picture by digital image processing technology. The contour in picture is proportional to the actual one, and the ratio is a constant K determined by CCD camera magnified ratio. Calculating the geometry parameters and comparing with the definition size, we can judge it whether qualified.This paper uses the median filter to smooth image, and the purpose is to reduce the interferers. According to the test, we can make the conclusion that the median filter result is better than other results, because the image is clearer and the contour line is well preserved.Unless getting the contour line, you can not detect the geometry parameters of thread. This paper uses the Canny operator to detect edge to find 2-D contour line. After this, it need trace the contour. The purpose of tracing the contour is to get the more perfect contour line.Finally, a testing program is developed with the function of data-collection, image processing and sizes calculation. The original data file , image processing and measuring result can be saved.