Complex field reconstruction using gradient and intensity measurements from a Shack-Hartmann wave front sensor

In many adaptive optical systems the standard wave front sensing and reconstruction process involves a conventional least squares reconstruction of gradient measurements obtained from a Shack-Hartman wave front sensor (WFS). This reconstruction algorithm assumes the WFS measurements are equal to the average phase gradient within each subaperture. However, this assumption does not account for the effects of scintillation in the wave front. As scintillation increases, intensity fluctuations in the wave front increase the disparity between the output of the WFS and what the reconstruction algorithm expects, which in turn causes a degradation in the performance of the reconstructor. We present an algorithm that attempts to mitigate the scintillation problem by reconstructing the real and imaginary components of the wave front using gradient and intensity information obtained from a Shack-Hartmann WFS. This algorithm estimates the wave front by inverting a more precise model of the WFS measurement process. Wave optics simulations over a variety of atmospheric conditions are used to compare the performance of our algorithm against a least squares reconstructor and a complex exponential reconstructor.