Laser beam focussing using parallel auxiliary beam - uses objective to focus auxiliary beam onto surface giving required main beam focus

摘要

An auxiliary parallel laser beam in the visible wavelength range is superposed on the main laser beam, so that both beams are focussed by the same objective (4). One or both beams are so influenced by optical means, that focal points of the two beams are at a required distance. The object surface is then placed at the focal point (7) of the visible beam. The main laser beam comes to a focus (8) further away from the objective than the auxiliary beam, so that when the auxiliary beam is focussed on the surface a patch or microarea is illuminated by the main laser beam.