DEVICE AND METHOD FOR DETERMINING THE FOCUS POSITION OF A HIGH ENERGY BEAM

An apparatus includes a focusing element arranged to focus a high-energy beam on a workpiece, an image detector for recording at least one image of an area to be monitored on the surface of the workpiece and/or the reference contour; imaging optics arranged to (a) receive process radiation radiation through the focusing element, from an area of the workpiece and/or the reference contour to be monitored, in the form of a first monitoring beam that is non-coaxial with the high-energy beam between the workpiece and the imaging optics and (b) redirect the first monitoring beam to the image detector to provide the at least one image of the area to be monitored and/or the reference contour; and an evaluation device operable to determine the focus position of the high-energy beam based on the at least one recorded image.