Convenient method for calibrating nonlinear phase modulators for use in phase shifting interferometry

A method to calibrate a nonlinear phase modulator is de- scribed that is based on the minimization of a function obtained from a sequence of interferometric images. The method is equally applicable to smooth wavefront and speckled wavefront interferometry, allowing con- venient in situ calibration for a wide range of interferometer configura- tions. The main advantage over previous calibration methods is that both the linear and quadratic phase variation terms are measured. The per- formance of the proposed method is verified by experiments in which the phase shift is determined independently by a Fourier transform method. © 1998 Society of Photo-Optical Instrumentation Engineers. (S0091-3286(98)02709-3) Subject terms: Calibration; piezoelectric translator; phase-shifting interferometry; phase modulator.