New simple ESPI configurations for deformation studies on large structures based on diffused reference beam

Two simple Electronic Speckle Pattern Interferometer (ESPI) configurations have been devised based on diffused reference beam which provides out-of-plane displacement data over the whole field. Both configurations use a tiny diffuser to generate the reference beam. This makes the system insensitive to reference beam misalignment, simplifies the construction of ESPI setup and allows larger area of observation unlike with conventional ESPI system. Thermal deflection studies on a cantilever plate have been carried out. Experimental results and features over the conventional ESPI system are discussed.