In-plane and out-of-plane displacement measurement in a wide dynamic range with a modified ESPI system
Pierre M. Boone, Ventseslav Sainov, Johan E. van der Linden · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 1995
Presented is the possibility of full-field displacement measurement in a wide dynamic range, using the hardware and software of a standard ESPI system. In-plane displacement measurements are performed by double symmetrical ullumination of the object, successively for each illumination direction, at a step-wise increase of the loading. The final result is the sum of the individual displacments for each loading step, thus overcoming the constraints due to decorrelation of the interference patterns, and ensuring high accuracy in a wide dynamic range. The out-of-plane displacements are measured by the method of interference fringe projection. The phase-stepping technique with digital processing of interference patterns provides high accuracy in a wide dynamic range, as well as real-time observation of displacements, typical for TV ESPI systems. Presented are experimental results; the prospoects for additional noise filtering are pointed out.