Vortex beam–Fizeau interferometer using the rotational four-step phase-shifting method

The vortex beam interferometer has attracted great attention in optical metrology. Specifically, the common-path Fizeau vortex interferometer exhibits obvious advantages in high-precision optical surface profile measurement, but it has never been fully reported on. In this study, we propose a vortex beam-Fizeau interferometer and achieve high-precision optical profile measurement using the rotational four-step phase-shifting method. In particular, we introduce angular phase shifts by rotating the tested object four times. Compared with the measurement results obtained from a commercial Fizeau interferometer, the measurement profile deviations of our method are 1.5164<i>λ</i> (peak to valley) and 0.0933<i>λ</i> (root mean square), with the root mean square error of the measurement profile deviation being less than 9.33%. This work offers a reliable scheme for the application of vortex beam interferometers in optical surface measurement.