A Demonstration of Wavefront Sensing and Mirror Phasing from the Image Domain

In astronomy and microscopy, distortions in the wavefront affect the dynamic range of a high contrast imaging system. These aberrations are either imposed by a turbulent medium such as the atmosphere, by static or thermal aberrations in the optical path, or by imperfectly phased subapertures in a segmented mirror. Active and adaptive optics (AO), consisting of a wave-front sensor and a deformable mirror, are employed to address this problem. Nevertheless, the non-common-path between the wavefront sensor and the science camera leads to persis-tent quasi-static speckles that are difficult to calibrate and which impose a floor on the image contrast. In this paper we present the first experimental demonstration of a novel wavefront sensor requiring only a minor asymmetric obscuration of the pupil, using the science camera itself to detect high order wavefront errors from the speckle pattern produced. We apply this to correct errors imposed on a deformable microelectromechanical (MEMS) segmented mirror in a closed loop, restoring a high quality point spread function (PSF) and residual wavefront errors of order ∼ 10 nm using 1600 nm light, from a starting point of ∼ 300 nm in piston and ∼ 0.3 mrad in tip-tilt. We recommend this as a method for measuring the non-common-pat