Quantitative wavefront sensing with static Foucault and pyramid tests

Abstract

Wavefront sensors (WFS) are now core components in the fields of metrology of optical systems, biomedical optics and adaptive optics systems for astronomy. Nowadays, the most popular WFS is the Shack-Hartmann, which is fully static but suffers from a limited spatial resolution in the pupil plane of the tested optical system. Higher spatial resolutions are achievable with other types of sensors, e.g. the pyramid WFS that requires temporal modulation of the recorded signals and implies high mechanical and electronic complexity. This paper examines the possibility of performing quantitative wavefront sensing inspired from the well-known Foucault test and only comprising static, non-modulated optical components. Here, two candidate designs of static WFS are proposed, based on a set of reflective prisms. Those prisms may be coated with gradient density filters. A simplified mathematical model allows for the definition of the wavefront slopes reconstruction formula and for the calculation of the wavefront itself. Numerical simulations demonstrate that the wavefront measurement accuracy is compliant with classical diffraction limit criteria when using coated prisms. Thus accurate WFE measurements are feasible in that case.