Abstract: A wavefront sensing and compensating system for detecting and correcting for distortion in light wavefronts is described in which the wavefront is divided into a plurality of subapertures and light intensified and imaged as spots of light from each subaperture onto a detector array. The individual detector elements of the array form a plurality of electrical signals proportional to the local divergence of the vector gradient field (.gradient..sup.2 .phi.). This .gradient..sup.2 .phi. signal after interfacing or reconstruction is applied to corrective mirrors which may be of the deformable or membrane type.