An approach for wavefront reconstruction based on a defocused Shark–Hartmann sensor is proposed.In this approach, not only the first-order origin moment (local slope of the input wavefront) but also the second-order central moment (local curvature of the input wavefront) of each spot in the intensity pattern is used to reconstruct the input wavefront.

By introducing the second-order moment, an improvement of reconstruction accuracy can be obtained. As the ambiguity of the sense of the local curvature of the input wavefront exists in the scheme of the conventional Shack–Hartmann sensor in focus, a defocusing scheme is adopted to solve this problem. Based on modal and zonal methods, respectively, the corresponding algorithms are invoked to reconstruct the wavefront from the map consisted of both local slopes and curvatures.

Numerical experiments show that the reconstructed wavefront by the proposed method is more accurate, in comparison to the result by the conventional method. It should be mentioned that the defocused sensor used in the proposed method sacrifices, to some extent, the dynamic range of measurement.