<title>Phase-shifting interferometry with precise phase steps</title>

Abstract

This paper presents an algorithm of phase-shifting interferometry with precise phase steps. In the algorithm, the phase steps between the interferograms captured by a CCD camera are taken as unknowns and they are directly determined by fringe pattern matching with subpixel resolution. The algorithm is therefore inherently free from the phase step errors caused by air turbulence, thermal drift, mechanical vibration, miscalibration and nonlinearity of the phase shifter. The computer simulation in the 3D surface measurement has shown that fringe pattern matching is effective in phase-shifting interferometry to find the phase steps from the interferograms with equi-spaced fringe patterns. In addition, this algorithm is potentially useful in the measurement of the physical quantities that are related to optical phase changes such as length and displacement.