In this project the dependence of the optical resolution of interferometers on the incident angle of the illuminating light is researched. To realize illumination under different distinct incident angles, different annular apertures are implemented into the system, so that they are imaged into the pupil plane of the objectives. When the incident angle changes, also the k_z component of wave vector changes. Depending on the sample surface and its spatial frequencies the light will be scattered under different angles, so for distinct incident angles only distinct spatial frequencies of the surface will participate in the signal formation. Since the phase evaluation of an interferogram can be performed at different evaluation wavelengths, the goal of this project is to researched how the optimal incident angles and evaluation wavelengths can be chosen to obtain the best possible results for different spatial frequencies of various surfaces. Furthermore, different illumination wavelengths will be used to realize different incident angles at the same time and thus combine the most favorable settings for different spatial frequencies.