Scene-based Shack-Hartmann wave-front sensing: analysis and simulation.

In many situations it is not possible for an adaptive optics system to use a point source to measure the phase derivative, such as imaging along slant paths through the atmosphere and observation of the earth from space with a lightweight optic. Instead, small subimages of the observed scene can be used in a scene-based wave-front sensing technique. This study presents three important advances in the understanding of this technique. Rigorous analysis shows how slope estimation performance depends precisely on scene content and illumination. Scaling laws for changes in illumination are derived. The technique, when applied to point sources, is more robust to detect size changes and background levels than current methods.