Slope measuring deflectometry allows the non-contact measuring of curves surfaces like ultra-precise elliptical cylinder shaped mirrors in use for the focusing of Synchrotron light. This paper will report on the measurement of synchrotron mirrors designed to guide and focus Synchrotron light in the variable polarization beamline P04 at the PETRA III synchrotron at DESY (Hamburg). These mirrors were optimized by deterministic finishing technology based on topography data provided by slope measuring deflectometry. We will show the results of the mirror inspection and discuss the expected beamline performance by ray-tracing results.