Automated simultaneous calibration of a multi-view laser stripe profiler

We present enhancements of existing calibration methods that allow the automated calibration of a laser stripe profiler in an industrial environment. The first and most important enhancement is a new design of the calibration object. Basically it is a "wire-frame model" of a cube, where the edges are simply standard aluminium profiles. This allows establishing point correspondences in a simple and robust way without the need of intensity information. Furthermore this hollow kind of a calibration object allows simultaneous multi-view calibration since enough points of six different planes can be seen from many directions. Given a rough calibration (based on rough measurements with +/- 50% accuracy) the scanned points can be automatically allocated to the respective planes of the calibration object. Secondly we propose a new way of solving the linear model of a laser stripe profiler. By firstly solving the camera-independent geometry these values can be averaged over the multiple views, which further reduces the local offsets of point clouds and therefore enhances the output of subsequent operations like mesh generation on the combined calibrated point cloud. The paper describes the design of the calibration object and the calibration method in detail and presents experimental results on simulated and real range data sets. The industrial applicability has been demonstrated in a sensor cell with four cameras under real-world conditions including moderate oscillations of the calibration object.