VIBRATION IN PHASE-SHIFTING INTERFEROMETRY

Unexpected mechanical vibrations can significantly degrade the otherwi se high accuracy of phase-shifting interferometry. Fourier analysis of phase-shift algorithms is shown to provide the analytical means of pr edicting measurement errors as a function of the frequency, the phase, and the amplitude of vibrations. The results of this analysis are con cisely represented by a phase-error transfer function, which may be mu ltiplied by the noise spectrum to predict the response of an interfero meter to various forms of vibrat0ion. Analytical forms for the phase e rror are derived for several well-known algorithms, and the results ar e supported by numerical simulations and experiments with an interfere nce microscope.