The optical characterization of micro- and nanoparticles often needs to meet high-quality standards. To control the fabrication of those structures highly precise measurement methods are necessary. In this project a Linnik interferometer is used to optically measure structures like this. The research focus lies on the development of a measurement method to reliably detect small deviations from a desired topography. To achieve this the interferometer does not have a planar mirror in the reference arm, but a reference object of known geometry and quality. When a depth scan of the object is performed in the measurement arm the difference to the reference geometry is measured and not the topography of the object itself. This project is a collaboration with the institute of nanostructures and analytics (INA) of the university of Kassel, that is providing the measurement structures.