Patent ID: 7359817

Claim:
A method of re-calibrating a three-dimensional visual sensor holding a plurality of parameters relating to calibration in a robot system, said method comprising the steps of: (a) moving a robot which supports at least one of the three-dimensional visual sensor and a measurement target to a calibration position to place the three-dimensional visual sensor and the measurement target in at least one optional relative positional relation while the three-dimensional visual sensor is in a state capable of normal measurement, measuring the measurement target by the three-dimensional visual sensor to acquire position/orientation data indicative of at least one of position and orientation of the measurement target with reference to a sensor coordinate system by using the parameters relating to calibration then held by the three-dimensional visual sensor, and storing the position/orientation data; (b) moving the robot to the calibration position of step (a) to place the three-dimensional visual sensor and the measurement target so as to reproduce the at least one relative positional relation at least approximately when the three-dimensional visual sensor is to be recalibrated after the three-dimensional visual sensor was in said state, and then measuring the measurement target by the three-dimensional visual sensor to acquire feature amount data on the measurement target with reference to an imaging plane coordinate system of the three-dimensional visual sensor; and (c) updating the parameters relating to calibration of the three-dimensional visual sensor, based on the feature amount data and the position/orientation data.