Real-time displacement and vibration measurements using a spatial phase-shifting technique

Real-time displacement and vibration measurements are presented, Which are based on a spatial phase-shifting with a tilt holographic interferogram. Three intensity data sampled at every one-third of the fringe spacing of the tilt fringes are used to calculate the phase and the modulation term of the fringe which are functions of a displacement and a vibration amplitude, respectively. Three-dimensional look-up tables perform the calculations in a TV repetition rate to give a phase distribution and a new fringe profile which contours the vibration amplitude. Experimental results are given in two cases of a displacement measurement for a cantilever-like object and a vibration measurement at resonant frequencies of a flat speaker.