High dynamic range wavefront sensing via digital moiré shearing interferometry

Aspherical, free-form, and off-axis asymmetric optical elements often exhibit high dynamic range wavefront errors (HDR-wavefronts) during measurement. Wavefront sensing technology can currently be broadly categorized into two main types: interferometric and non-interferometric. Interferometric methods, with their high precision, occupy a significant position in optical detection. However, they are susceptible to modulation of the interference fringes, particularly in regions where the wavefront gradient changes rapidly. When the density of interference fringes is too high, insufficient sampling can occur and significantly reduce measurement accuracy. To address these limitations, we propose a wavefront sensing approach that integrates digital moiré fringe analysis with shear interferometry. By combining the frequency-domain control capabilities of digital moiré techniques with the gradient sensitivity of shear interferometry, this method enables pixel-level, digitally tunable shear magnitude. This digital control alleviates the strict dependency on shear precision inherent in conventional shear interferometry. Meanwhile, as shearing interferometry measures the differential phase of the wavefront, in principle, it has the characteristic of alleviating high-frequency fringes. Furthermore, the decreased fringe density enhances the performance of phase-shifting algorithms, leading to more accurate phase retrieval. As a result, it facilitates the efficient measurement of HDR-wavefronts. Both simulation and experimental results on aspherical surface measurements show that the proposed method achieves high accuracy and stability in reconstructing HDR-wavefronts induced by aspherical surfaces. This technique provides an innovative solution for characterizing complex optical surfaces and highly aberrated optical systems, with significant engineering applications.