Research Of Workpiece3-D Size Measurement Based On Machine Vision

Owing to modern manufacturing require high-precision and high-efficiency to detection technology, computer vision avoiding the inconvenience of traditional testing and the inaccuracy of special inspection is playing an increasingly important role in modern industry, by virtue of its real-time and non-contact detection features.Basing on computer vision, workpiece size detection system introduces computer vision to the workpiece site of the pipeline detection, which captures images of workpieces by binocular stereo vision system, detects the contour edge of the workpiece length, width and height after a series of image processing algorithms, calculates the world coordinates of the vertices of the workpiece and obtains the3D size of the workpiece according to the vertices.Using computer vision and around the3D size detection of workpiece, the system mainly researches contents on camera calibration, image preprocessing, contour detection,3D correction, stereo matching and3D reconstruction, in which the accuracy of camera calibration and stereo matching is the key of3D reconstruction.Camera calibration utilizes Matlab self-calibration toolbox to calibrate the left and right cameras and accesses to internal and distortion parameters; then stereo calibration for two cameras to get the relative relationship and analyzes experimentally according to the re-projection error on calibration results.By epipolar rectification to left and right images, Stereo correction realizes parallax error only exists in the x-direction not in the the y-direction in the two images; stereo matching, by the feature point detection and precise matching for the images of epipolar line correction, is ready for subsequent3D reconstruction.Size detection, using the Hough transform to detect the edge of the workpiece and seeking the intersection of the two straight-line, solves the image coordinates of each vertex of the workpiece;then combing with the triangulation method, solves the world coordinates of each vertex and calculates the3D size of workpiece. Combination of binocular stereo vision algorithm, achieving a three-dimensional reconstruction of the workpiece.