Pyramid based locally closed loop wavefront sensor: an optomechanical study.
Magrin D. (a), Dima M. (a), Farinato J. (a), Ragazzoni R. (a), Viotto, V. (a)(b)
a) INAF - Osservatorio Astronomico di Padova b) Universita’ di Padova - Dipartimento di Astronomia
Pyramid wavefront sensors have shown their ability to achieve ultimate performances in terms of usage of starlight photons. Several of these advantages, however, does relay on the fact that the starlight is focused onto the pyramid pin after being properly corrected. While conventional adaptive optics systems (including multi conjugated ones) automatically imply such a feature this is not true for Multi Objects or non conventional Multi Conjugated AO systems, or more in general for the ones where the compensated area is somehow different from the area searched for references. We develop the concept of locally closed loop systems in a compact way along with various approaches to metrologically measure the wavefront with enough absolute accuracy, in contrast with the accuracy to vanish the residual in the conventional use of wavefront sensors. We show an optomechanical study including a preliminary error budget and a choice of existing components in order to achieve the goal of detailed wavefront sensing with high dynamic range on the faintest references where a pyramid sensor can achieve significant results.