Calibration of the laser displacement sensor and integration of on-site scanned points

Abstract

On-site inspection with a laser displacement sensor installed on the spindle of a three-axis machine tool has found a wide range of applications in industrial processes. The calibration of the beam direction and the integration of the on-site scanned points are crucial for the measurement of free-form surfaces. This paper presents a method to calibrate the unit direction vector of the laser beam and integrate the on-site scanned points based on a standard ball. By scanning the fixed ball, a group of nonlinear equations is constructed. The nonlinear equations are solved by the Levenberg–Marquardt algorithm to get the unit direction vector of the laser beam and the center position of the standard ball. Then the coordinate transformation parameters between the world coordinate system and the sensor coordinate system are calculated. The scanned points from different coordinate systems are transformed into the world coordinate system by the coordinate transformation. The method simplifies the traditional calibration process and realizes the integration of the multi-angle scanned points on a three-axis machine tool. The feasibility and effectiveness of this method are verified through simulation and practical experiment. By comparing fitting value under different measuring conditions with the nominal, the measurement parameters including the incident angle and the scan depth are optimized. In the experiment, the measurement accuracy of this method reaches 0.02 mm.