Calibration of alignment errors of quadriwave lateral shearing interferometer for testing high numerical aperture spherical wave with oblique incidence

Alignment errors in quadriwave lateral shearing interferometry (QWLSI), such as grating tilt, detector tilt, and relative rotation between grating and detector, are critical factors affecting measurement accuracy. Traditional calibration techniques for alignment errors primarily focus on plane waves or low numerical-aperture (NA) spherical waves under normal incidence. However, these methods are inadequate for complex situations involving high-NA (NA > 0.35) spherical waves under oblique incidence. This paper proposes a geometric optical theoretical model based on higher-order Taylor expansion to systematically analyze the impact of alignment errors like detector tilt when testing high-NA spherical waves under tilted incidence. Theoretical analyses and simulations indicate that in measurements of high‑NA spherical wavefronts, the combined effects of detector tilt and oblique incidence primarily introduce coma as the dominant aberration, whose magnitude varies with both factors. The alignment experiment results from a QWLSI validate the proposed theory, showing less than 6 % relative error between experimental and theoretical results.