Zonal wavefront sensing using a grating array without a reference wavefront

In the present work, we propose a reference-free sensing scheme in a grating array-based wavefront sensor such that the stringent requirement for an independent array of high-quality reference spots in a zonal wavefront sensor can be eliminated. The proposed sensing scheme employs an array of local grating-induced diffraction to encode phase gradients directly into the +1 and -1 diffraction spots, recorded using a single camera frame, in contrast to the conventional Shack-Hartmann wavefront sensor or interferometric systems, which call for either a known reference or intricate calibration. Thus, the proposed scheme transfigures a serious physical problem, where capturing reference spots is either impractical or impossible, into a computational problem that can be resolved with minimal effort and without increasing the system's complexity. We provide proof-of-concept simulation and experimental results to demonstrate the feasibility and effectiveness of the proposed sensing scheme.