Two-frame wavefront reconstruction method with nonlinear optimization for Ronchi lateral shearing interferometry.

Ronchi lateral shearing interferometry is widely applied in wavefront measurement of advanced lithography tools. In Ronchi lateral shearing interferometry, higher-order diffraction beam interference is a common challenge, currently mitigated by introducing more phase shifts, resulting in extended measurement times and added errors. In this study, we propose a nonlinear optimization approach that combines a 2-frame phase-shifting algorithm to suppress the influence of high diffraction orders, reducing the required number of phase shifts by more than 75%. We formulate a numerical model that aligns with the interferometry, construct a highly robust error function, and enable high-precision wavefront reconstruction by optimizing Zernike coefficients. The accuracy and robustness of the proposed method are verified through simulations and experiments. • The two-frame algorithm is employed for approximate wavefront reconstruction. • A robust loss function mitigate high diffraction order interference. • Nonlinear optimization achieves highly accurate wavefront reconstruction. • It reduces the number of required phase shifts by more than 75%. [ABSTRACT FROM AUTHOR]