Three-Dimensional Phase Evaluation in ESPI by Using a Non-Cube Beam-Splitter

Simultaneous measurement of three-dimensional phase distributions by Electronic Speckle Pattern Interferometry (ESPI) is presented using a Non-Cube Beam-Splitter (NCBS). By using the NCBS light from a tested object and from a reference surface can be combined and recorded by a CCD camera. Three carrier patterns are introduced by tilting the reference surface a small angle. The tested object images are recorded before deformation, after titling the reference surface, and then after deformation when three laser beams illuminate the test object and the reference surface at different incident angles respectively. Three carrier patterns and three modulated carrier patterns are obtained by image subtraction. Then three phase maps can be demodulated by using Fourier transform, from which the phase distributions in x, y and z direction are separated respectively. The principle is presented and a typical three-point bending experiment is completed. Experimental results are offered.