Phase-shifted image matching algorithm for displacement measurement

An algorithm of phase-shifted image matching for the measurement of displacement from interferometric images is presented. The algorithm is capable of detecting the displacements between the interferograms captured by a CCD camera with subpixel accuracy. The phase curves are obtained from mean-square-difference calculations of any two fringe patterns shifted pixel by pixel, and the phase differences between the interferograms are computed by interpolation. An example of measurement of electrostatic force displacement by a fiber optic interferometer system is described. The experiment shows that the algorithm has the advantages of high measurement precision and high resistance to noise. The high resistance to noise of the algorithm makes it suitable for measurement even in harsh environmental conditions. (C) 1996 Society of Photo-Optical Instrumentation Engineers.