Sub-Nanometre Validation of a Deformable Mirror Concept*

Highly accurate optical systems may suffer from heat induced optical aberrations, causing blurred images, or degraded sensing properties. Correcting these aberrations with nanometre precision requires a dedicated design of a deformable mirror and a measurement set-up that can validate the design. In this paper we focus on the quantitative validation of the measurement set-up and the deformable mirror. To obtain nanometre precise measurements vibration isolation, turbulence isolation, beam enhancement and static noise reduction are applied. This resulted in a repeatability of 0.35 [nm] and reproducibility of 2.0 [nm]. With these known characteristics, an uncertainty analyses is carried out on an actuated shape of the deformable mirror, which is 50X50X4 [mm]. The stability of a deformed shape is 0.46 [nm] RMS and the difference with the modelled deformation is 2.0[nm] RMS on an amplitude of 30 [nm]. These low numbers quantify the validity of the actuation concept.