Compact PMD measurement and PSF reconstruction for large mirrors

Phase measuring deflectometry (PMD) is currently used to inspect the astronomical mirrors of the Cherenkov Telescope Array (CTA). In this project, about 10,000 mirror tiles will be mounted on the telescopes. For a 100% test, certain requirements regarding the spatial extent of the PSF have to be fulfilled. Due to the large radius of those mirrors (~33 m), it is not possible to measure the PSF directly within the limited space of a laboratory. We implemented a PMD sensor with a footprint 4 x 3 x 2 m3 which fits into the existing climate chamber. Moreover, this technique allows the reconstruction of the PSF for a real case scenario (the light source in infinity and off-axis) which is not possible for direct PSF measurement (the point like source in 2f and on-axis). We will present our PMD solution and discuss how to optimally reconstruct the PSF from stitched spatially resolved data. Additionally, results for different mirror types and environmental conditions will be presented.