Synchrotron radiation based emittance diagnostics at modern 3r d generation light sources is mainly based on beam profile imaging in the X-ray region in order to overcome the resolution limit imposed by diffraction. A possibility to circumvent this limitation is to probe the spatial coherence with a double-slit interferometer in the optical spectral region. The light source PETRA III at DESY is using this type of interferometer since several years in order to resolve vertical emittances of about 10 pm.rad. The device is set up behind a 30 m long optical beamline, connecting the accelerator tunnel and the optical hutch. In order to increase the measurement stability, a much shorter optical beamline with reduced number of optical elements was recently commissioned. At the end of the beamline, a two-dimensional interferometer was installed which allows to deduce transverse emittances in both planes simultaneously. This contribution summarizes the status of beamline and interferometer commissioning.