AN APPARATUS FOR DETERMINING THE POSITION OF THE FOCAL POINT IN A LASER MACHINING SYSTEM

摘要

The invention relates to an apparatus for determining the position of the focal point of a laser beam in a laser machining system in which the laser beam is transmitted via an optical fibre (9) to the workpiece (3) to be machined by the laser beam. The z coordinate position of the focal point is determined by means of a mirror (6, 16), for reflecting some of the laser radiation back towards the end surface (1) of the optical fibre, and a detector (11) arranged between the laser (8) and the outgoing fibre (9) for measuring the radiation reflected back through the fibre.