A device and a process for processing and/or joining work pieces via laser radiation, with an effective power laser and a pilot target laser that emit laser beams of different wavelengths, with the laser beams being directed at the work pieces by laser optics. Regarding the laser beams, by the laser optics that comprise at least one diffractive optical element (DOE) as a masking system, the beam pattern of the pilot target laser is adjusted to match the beam pattern of the effective laser beam. This is accomplished preferably by removing the pilot laser beam from the effective laser beam for part of the path length by dichroic mirrors, and by expanding the diverging pilot laser beam on said part of the path length by deflecting mirrors whose distance from the dichroic mirrors is variable.