Abstract: A writing laser beam and a scanning laser beam are coaxially superposed for position determination and for correcting mechanical movements during the writing of lines of a desired pattern into a metalized three-dimensional integrated circuit. The coaxially superposed writing and scanning laser beams are directed, using a single beam splitter for the scanning laser beam, to a lens head and to a workpiece as well as to a turret for alternately employing one of a number of measuring or observing instruments. The individual members are precisely adjustable and during automatic evaluation of the thus determined values, correction of any error that may occur, can be directly obtained at the desired rate by such automatic evaluation. In order to properly arrange and shorten the radiation paths there is used a laser beam collimator which preferably is also provided with a writing laser beam detector. Furthermore, a scanning laser beam detector can be arranged to follow the beam splitter for the scanning laser beam.