Operating on materials by means of a high-energy laser beam - with focal position varied by means of deformable mirror surface, with focal spot unaltered in size, to cut thick metal sheets

摘要

The method for operating on materials by means of a high-energy laser beam uses a deformable mirror in front of a focussing systm to influence the beam divergence. Increases of the beam divergence takes place so close to the focussing system that the axial focal position is varied with the focal spot essentially remaining unaltered in size. The installation incorporates a variable optical system (17). The system includes a mirror surface (18) whose convexity in front of the focussing system (14) can be varied. Beam divergence is varied periodically. Focal position variation is combined with feed motions. The variable optical system takes the place of a deflecting mirror and is located in the focussing head (11). A preloaded piezoelectric actuator (19) located behind the mirror surface (18) and controlled by a voltage source (21) is used to adjust the position of effective focus (F,F'). USE/ADVANTAGE - For welding and cutting operations. In constrast to known installations (with constant focal positions), it can be used effectively to cut thick metal sheets (e.g. with thickness of the order of 20 mm).