Vibration measurement using phase-shifting speckle-pattern interferometry

Abstract

Digital speckle-pattern interferometries for the measurement of a vibration amplitude are presented, based on phase shifting of a speckle interferogram. The calculation of the square root and division with phase-shifted speckle interferograms give a high contrast fringe pattern, which contours a vibration amplitude regardless of a bias deformation of the vibration. The arctangent calculation with phase-shifted fringe patterns gives the phase distribution proportional to the bias deformation of the vibration, which is obtained by the correction of phase discontinuities of ±2π and ±π in the phase image. The detection of the phase discontinuity of ±π in the phase image gives the center line of a dark fringe in the calculated fringe pattern. The fringe-order numbers are determined by referring to the new calculated fringe pattern. The distribution of the vibration amplitude is obtained by the interpolation of the fringe-order numbers.