Direct phase aberration compensation through gradient fitting for wafer surface 3D measurement using digital holography

Digital holography is a widely used method for quantitative phase imaging. However, the object wave contains phase aberrations introduced by the imaging lenses. A multitude of techniques have been proposed to compensate for the phase aberrations, and most of them require a phase unwrapping procedure before compensation, which can be easily affected by any unwrapping error caused by discontinuity boundaries. To address this problem, we propose a direct phase aberration compensation method based on phase gradient fitting without phase unwrapping. We use a bivariate polynomial model to describe the distribution of the phase aberrations. The fitting procedure is based on comparisons between the phase gradients described by the model and those calculated from the actual wrapped phase distribution. Simulations and experimental results for 3D measurement of the wafer surface demonstrate that our method outperforms state-of-the-art approaches, proving its effectiveness in compensating the phase aberrations.