Phase-shift calibration errors in interferometers with spherical Fizeau cavities

Phase-demodulation algorithms in interferometry often depend on a sequence of evenly spaced reference phase shifts. These phase shifts must be accurately calibrated and can be distorted by geometric effects, especially when spherical components with high curvature are tested. Here the resulting measurement errors are quantified through mathematical analysis, and it is shown that modern phase-estimation algorithms can be effective in a spherical Fizeau cavity with a numerical aperture as large as 0.95.