Low-light-level adaptive optics for a two-telescope interferometer scheme

We study the use of a cross-correlation algorithm as a sub-aperture slope estimator in a low light-level adaptive optics scheme for a two-telescope interferometer. Using a computer simulation of a Hartmann-Shack wavefront sensor to compare the algorithm against a conventional intensity-centroid estimator, we find that the cross-correlation algorithm marginally reduces the mean-square slope-measurement error under shot-noise limited conditions and significantly reduces the error in the presence of additive noise. We compare the performance of the two estimators in a two-telescope interferometer scheme by introducing wavefront sensor noise with appropriate variance in a full adaptive optics simulation, calculating measures-of-merit appropriate to interferometric imaging such as fringe visibility and coherent energy.