With a super luminescent diode a) and a measuring probe c) connected via a fiber coupler b), the information about the time difference of the light reflected at the probe exit surface d) and the workpiece surface e) is measured .c) and the workpiece surface e) is projected by the interferometer (imaging optics f), beam splitter g), mirrors h) and i) and cylindrical lens j) onto a line camera k) and the distance is determined from this.