Synthetic aperture phase-shifting interferometry for high-numerical-aperture spherical surface measurement

Reduction of Spherical Aberration Measurement Error in High-Numerical-Aperture Spherical Test with Synthetic-Aperture Fizeau Interferometry

“…The reference surface was translated toward the object surface by a distance λ and 13 interference images were recorded at equal phase-shift intervals of π/3. The object phase distribution Mx, y) was calculated by a single 13-frame error-compensating algorithm [3] over the whole aperture (hereafter, the conventional method). Second, the object phase was also calculated using the same interference images region by region using seven algorithms that were designed with phase steps of 2S/6, 2S/7, 2S/8, 2S/9, 2S/10, 2S/11, and 2S/12 rad (hereafter, the synthetic aperture method).…”

“…and Nanotechnology (ASPEN 2022) 15-18 November 2022, Singapore. Edited by Nai Mui Ling Sharon and A. Senthil Kumar phase modulation nonuniformity; H is the 2 nd -order PZT extension nonlinearity; R is the average reflection index for the surfaces; and J, K i , and L i are the lowest-order error coefficients [3]. The magnitude of phase measurement error 'M can be estimated if we can uniformly change the initial value of the object phase M. In a monochromatic interferometer, the initial phase variation can be introduced if we mechanically shift the initial position of the reference surface with the PZT.…”