Two-wavelength phase-shifting interferometry using an electrically addressed liquid crystal spatial light modulator

A two-wavelength moire phase-shifting interferometer using a liquid crystal spatial light modulator is developed. The optical phase shifts for the two wavelengths are simultaneously given by a digital phase shift of the grating displayed on the spatial light modulator. A phase shift of the moire fringe is achieved by equal phase shifts with opposite signs in diffracted beams with opposite diffraction orders. A moire phase-shifting interferometer with no moving parts and no requirement for calibration of the value of the phase shift was realized. Our experimental result shows measurements of the profile of a step object with a 12.0-mum synthetic wavelength. (C) 2004 Elsevier B.V. All rights reserved.