Optical profiling based on vertically scanning white-light interferometry is a well established 3D measuring technique for more than one decade now. In recent years the area of application of these instruments tends more and more from laboratory to industrial applications, where robustness, compactness, and cost efficiency is required. A new instrument developed on the basis of a Mirau interferometer with a microscopic field of view meets important requirements of industrial use. Surface heights can be obtained with subnanometer resolution and the measuring setup is less sensitive to
vibrations, so that roughness measurements on optical surfaces are possible even in a harsh environment. However, principal limitations arise in certain applications, e.g. if optically smooth surfaces with either flanks, curvatures, edges, or grooves are to be measured. This contribution deals with phenomena, which become relevant in these cases. The occuring effects lead to differences in the results of coherence peak and phase analysis of the interference signals, and therefore may be the origin of ghost steps in the measuring results.