Automated stitching interferometry for high-precision metrology of X-ray mirrors

Automated stitching interferometry is essential for high-precision metrology of synchrotron X-ray mirrors; however, achieving robust automated alignment remains a technical bottleneck. This paper presents a comprehensive automated solution driven by a Zernike-based closed-loop feedback mechanism. Unlike conventional methods, our approach analytically decouples pitch and roll errors using Zernike coefficients, combined with a dynamic variable-gain logic to achieve monotonic convergence. We developed a hierarchical, asynchronous, multi-threaded control architecture that standardizes mechanical settling times, ensuring superior measurement repeatability. Rigorous validation on a 400 mm elliptical mirror yielded a residual error of 0.48 nm RMS with geometric parameter errors below 0.3%, while repeatability tests on a 600 mm flat mirror achieved a 0.17 nm RMS. These results demonstrate that the proposed control strategy significantly enhances both the measurement efficiency and the reliability of metrology for advanced X-ray mirrors in diffraction-limited storage rings.