Abstract: A process and apparatus for three-dimensional position control of the focal point of a high-energy laser beam by measuring its directional and focal point deviation. A portion of the energy of the laser beam is split off by means of a beam splitter extending over the whole cross-section of the laser beam and is focussed on a quadrant detector by means of an optical system which introduces an astigmatic aberration. The various patterns and pattern positions generated on the quadrant detector as a function of the defocussing and directional deviation are analyzed by means of an electronic system, and corresponding control signals are generated.

Abstract: For power lasers, the shape of the mirror is an essential factor for the quality of the mode. In addition, a power laser usually has a plurality of mirrors. The shape of the mirrors may change during operation, for example due to heating. According to the invention, a hollow space is provided on the rear side of the mirror and pressure is applied to this hollow space to a greater or lesser degree, so that the geometry of the mirror changes under its influence.