Noncontact 3-d coordinate measurement of cross-cutting feature points on the surface of a large-scale workpiece based on the machine vision method

Three-dimensional coordinate measurement of feature points on the surface of a large-scale workpiece is important and difficult. Various relative measuring methods have been presented in recent years, and the machine vision method has been paid more attentions by researchers. The application of the machine vision method in 3-D coordinate measurement of feature points on the surface of a large-scale workpiece is discussed in this paper, and an accurate, simple, and new measuring method is proposed. The design of the measuring system mainly considers the following aspects: 1) the principle and composition of the measuring system; 2) the monocular vision algorithm for camera locating; 3) the calibration algorithm of the charge-coupled device (CCD) camera; 4) the image processing algorithm of cross-cutting feature points and the calculation of their 2-D image coordinates; and 5) the binocular stereo vision algorithm for depth measurement based on the large-scale coordinate measuring machine. The experimental results indicate the correctness and reliability of the new measuring method, and we believe that it will be a reliable and efficient technique for the noncontact 3-D coordinate measurement of cross-cutting feature points on the surface of a large-scale workpiece.