Implementation of reference-less wavefront sensing in a grating array-based wavefront sensor

In the present work, we propose a novel reference-less wavefront sensing method in a grating array-based wavefront sensor (GAWS). The proposed sensing method utilizes both +1 and -1 diffraction orders. The key idea is that when there is a local tilt in the wavefront, the array of +1 and -1 diffracted spots move in opposite directions due to their optical phase conjugate relationship but share a common reference position. By determining the displacement of these spots, the reference position can be precisely determined, and the local slope can be extracted from which the incident wavefront can be estimated. The proposed sensing method facilitates wavefront estimation using a single camera frame and is compatible with standard wavefront estimation algorithms. This proposed method proves particularly advantageous in scenarios where a high-quality wavefront is unavailable as a reference. We have validated the effectiveness of our proposed method through simulation results.