Wavefront Correction of Extended Objects Through Image Sharpness Maximisation

Many adaptive optics systems rely on a wavefront sensor (WFS) to sense the aberrations in an incoming wavefront. The required corrections are determined and applied by the wavefront corrector - often a deformable mirror (DM). We wish to develop a wavefront sensor-less correcting system, as derived from the original adaptive optics system of Muller and Buffington[1]. In this experiment we apply commands to a corrective element with adjustable segments in an attempt to maximise a metric which correlates to image quality. We employ search algorithms to find the optimal combination of actuator voltages on a DM to maximise a certain sharpness metric. The "sharpness" is based on intensity measurements taken with a CCD camera. It has shown [2] that sharpness maximisation, using the Simplex. algorithm[3], can minimise the aberrations and restore the Airy rings of an imaged point source. The results are repeatable and so-called "blind" correction of the aberrations is achieved. This paper demonstrates that the technique can be applied to extended objects which have been aberated using a Hamamatsu SLM to induce aberrations. The correction achieved using various search algorithms are evaluated and presented.