description of fig1 in the embodiment according to fig2 a convex lens 10 that focuses emitter light beam 3 a is arranged behind light source 1 a yellow filter 9 pivotable into the beam path is arranged behind the convex filter a laser beam of a discrete wavelength ellipsometer 13 dwe is coupled parallel to emitter light beam 3 a via a stationary beam splitter 12 in first aperture 2 both beams undergo the same beam forming in fig2 the two beams are depicted above each other as one beam in particular both beams are reflected at the same measuring spot on sample 50 such that the laser beam of discrete wavelength ellipsometer 13 is also parallel to receiver light beam 3 b the laser beam of discrete wavelength ellipsometer 13 uses the same optical components and polarization optics as emitter light beam 3 a and receiver light beam 3 b the light source of discrete wavelength ellipsometer 13 in this case a laser diode has better stability than broadband light source 1 such that the quality of the measurements of the ellipsometer of the present invention is further improved the laser beam is evaluated on a photo diode of a laser detector 15 which has higher measuring accuracy than the multi wavelength detector in addition to improving the measurements the laser beam of discrete wavelength ellipsometer 13 is also used for adjustment and verification purposes for the calibration of the ellipsometer of the present invention furthermore in this embodiment a grey filter changer 11 is arranged behind first aperture 2 this grey filter is used to adjust the intensity of emitter light beam.