6DOF calibration of a camera with respect to the wrist of a 5-axis machine tool

Abstract

Computer vision systems are being used to guide machine tools fitted with wrist-mounted cameras. The vision system must measure the coordinates of objects with respect to the machine tool world reference frame. Therefore, the system must be calibrated by measuring the coordinates of the camera with respect to the wrist of the machine tool. The paper shows that the geometry of the camera views—that one is forced to use in practice—cause the calibration problem to be near rank- deficient. The writer thinks that this is the cause of inaccuracy in existing practical work in this area. The paper gives a closed-form solution of the calibration problem which handles the rank-deficiency. The results of the first real tests are reported.