Improving coaxial measurements in laser welding by correcting distortions of a laser focus lens with a wide field of view

A compact, lightweight, and multifunctional head for robotic laser welding applications has been equipped with a camera to provide a real time image stream of the work piece for seam teaching, tracking, and inspection purposes [D. Iakovou, R. G. K. M. Aarts, and J. Meijer, “Integrated sensors for robotic laser welding,” in Proceedings of the Third International WLT Conference on Lasers in Manufacturing, Munich, Germany (AT-Fachverlag GmBH, Stuttgart, 2005), pp. 121–126; D. Iakovou, R. G. K. M. Aarts, and J. Meijer “Sensor integration for robotic laser welding processes,” (paper No. 2301), in Proceedings of the International Congress on Applications of Lasers and Electro-Optics (ICALEO), Miami, 2005 (unpublished)]. The camera uses part of the laser focusing optics. Research has been done to identify and correct for positioning errors introduced by the optical system. A robust camera and lens calibration method has been developed. Calibration and seam detection experiments have been performed and the results were used for seam tracking.