In three-dimensional optical measurements systematic deviations between measured topography data and the real topography occur. This is especially true for surfaces with steep flanks, high curvatures and high-frequency structures. In order to reduce these deviations a fundamental understanding of the relevant physical effects and mechanisms plays a key role.

For this reason, we develop mathematical models, which consider both, the transfer characteristics of the instrument as well as the interaction between the incident light and the surface of the measuring object realistically. Besides analytical methods known from physical optics we also use rigorous simulation techniques, which directly result from Maxwell’s equations. In addition, the coherence properties of the light as well as aberrations of the measuring system are taken into account. Finally, optical measurement signals are simulated that can be analyzed with the same signal processing algorithms, which are also used for real measurement signals.

As shown in the figure, batwings are an example of typical measurement artefacts, which occur in white-light interferometry at steep flanks and perpendicular edges. The diagrams obtained from simulation and measurement results are in a good agreement.