Eye-hand-workspace calibration using laser pointer projection on plane surface

Purpose – The purpose of this paper is to propose a calibration method that can calibrate the relationships among the robot manipulator, the camera and the workspace. Design/methodology/approach – The method uses a laser pointer rigidly mounted on the manipulator and projects the laser beam on the work plane. Nonlinear constraints governing the relationships of the geometrical parameters and measurement data are derived. The uniqueness of the solution is guaranteed when the camera is calibrated in advance. As a result, a decoupled multi-stage closed-form solution can be derived based on parallel line constraints, line/plane intersection and projective geometry. The closed-form solution can be further refined by nonlinear optimization which considers all parameters simultaneously in the nonlinear model. Findings – Computer simulations and experimental tests using actual data confirm the effectiveness of the proposed calibration method and illustrate its ability to work even when the eye cannot see the hand. Originality/value – Only a laser pointer is required for this calibration method and this method can work without any manual measurement. In addition, this method can also be applied when the robot is not within the camera field of view.