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 (peak to valley) and 0.0933 (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.