Deformable mirrors with exchangeable substrates for variable astigmatism correction

The correction of surface shape errors is not only essential to optical systems, but becomes more and more important for optical metrology. We present a deformable mirror, which is suitable for the correction of astigmatism up to an amplitude of ±10 µm. The mirror substrate is exchangable, allowing for an easy adaptation to different spectral ranges. The design of the deformable mirror enables stable astigmatism amplitudes over several days according to the set-and-forget principle. A finite element analysis is performed to simulate the surface deformation, which is compared to measurements of a prototype. The adjustment accuracy is proven by repeatedly exchanging of two substrates and performing interferometric measurements of the deformation. Experimental measurements with the first prototype demonstrate a very high long-term stability.