An optical measurement arrangement includes an ellipsometer (45) and a device for ascertaining and correcting directional deviations between the line normal to the specimen surface and the angle bisector (25) between the incident and return beams (23, 24) of the ellipsometer (45). A measurement arrangement includes a mirror objective and a device for ascertaining directional deviations between the line normal to the specimen surface and the optical axis of the mirror objective, which has a deflection element in the unused aperture space of the mirror objective. A direction monitoring beam (30) is directed onto the specimen (P). An optical element for imaging the return reflection of the direction monitoring beam (30) onto an area detector that is connected to an evaluation circuit (46) is also provided. Positioning commands for a specimen stage (12) are available at the outputs of the evaluation circuit (46). By way of the control commands, the specimen stage is caused to tilt until the return reflection on the area detector has assumed the position at which the direction of the normal line corresponds to the direction of the angle bisector (25).