Accurate measurement of 3D coordinate of an object with subpixel technique

Accurate measurement of 3D position of an object is very important for industrial quality control, robot vision and 3D movement analysis etc. Close range photogrammetry is one of the common techniques for this purpose. Coupled with digital image processing techniques, close range photogrammetry has been developing very quickly in the last decade and has more and more applications. In this paper, we present an accurate 3D measurement method by a stereo camera system with a digital image processing subpixel technique. With the method, the stereo camera system is accurately calibrated and rectified with a rectangular grid. The specified object masks are extracted accurately and automatically by a pattern recognition method. Finally, the object masks on each camera image are matched automatically and the 3D position of the object is determined by the photogrammetric principle.