Hybrid Holographic Interferometer For Measuring Three-Dimensional Deformations

A method for automatically measuring the three-dimensional (3-D) deformations of a diffuse surface is studied, using a real-time holographic interferometer and a television-computer system. The object surface is illuminated from three different directions. The scattered waves are recorded on a thermoplastic hologram. Real-time holographic interference patterns are observed through the hologram in a fixed direction by sequentially applying the three illuminating beams. The three fringe patterns are put into the computer using a television (TV) camera. The relative fringe order numbers are determined over the whole surface. Calculations for obtaining 3-D deformation distributions are performed, and the results are displayed on a cathode-ray tube (CRT) monitor.