US Patent 7899577 Measuring system and calibration method

A measuring system and a calibration method for automatically calculating errors of mechanical parameters with high accuracy and correcting the parameters, by means of a relatively small and inexpensive measuring device. In relation to a plurality of positions of measurement, a robot is automatically moved such that, on a light receiving surface of a camera, the distance between the centers of an ellipse indicating a mark of a target and a circle of representing the shape of the target, and the difference between the length of the long axis of the ellipse and the diameter of the circle are within a predetermined error range.