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In astronomy and microscopy, distortions in the wavefront affect the dynamicrange of a high contrast imaging system. These aberrations are either imposedby a turbulent medium such as the atmosphere, by static or thermal aberrationsin the optical path, or by imperfectly phased subapertures in a segmentedmirror. Active and adaptive optics (AO), consisting of a wavefront sensor and adeformable mirror, are employed to address this problem. Nevertheless, thenon-common-path between the wavefront sensor and the science camera leads topersistent quasi-static speckles that are difficult to calibrate and whichimpose a floor on the image contrast. In this paper we present the firstexperimental demonstration of a novel wavefront sensor requiring only a minorasymmetric obscuration of the pupil, using the science camera itself to detecthigh order wavefront errors from the speckle pattern produced. We apply this tocorrect errors imposed on a deformable microelectromechanical (MEMS) segmentedmirror in a closed loop, restoring a high quality point spread function (PSF)and residual wavefront errors of order $\sim 10$ nm using 1600 nm light, from astarting point of $\sim 300$ nm in piston and $\sim 0.3$ mrad in tip-tilt. Werecommend this as a method for measuring the non-common-path error inAO-equipped ground based telescopes, as well as as an approach to phasingdifficult segmented mirrors such as on the \emph{James Webb Space Telescope}primary and as a future direction for extreme adaptive optics.

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