Phase retrieval in ESPI from a dense phase fringe pattern

Abstract

A method for phase retrieval from dense phase fringe in phase-shifting electronic speckle pattern interferometry (ESPI) using fast windowed Fourier filtering (FWFF) method is presented. Phase-shifting method is an accurate method in ESPI for phase retrieval. However, the wrapped phase map is corrupted by the speckle noise which will significantly affect the phase unwrapping technique to acquire the accurately unwrapped phase map. For relatively large deformation measurement, the wrapped phase map becomes dense and hence becomes difficult to be demodulated properly. Conventional sine-cosine average filtering technique is difficult to reduce the noise in such case. FWFF algorithm is useful for noise reduction of wrapped phase maps. In this paper we propose to measure relatively large deformation by reducing noise using FWFF. Both the simulation and experimental results are presented to show that the proposed method can efficiently reduce the noise of the dense wrapped phase map and the deformation can be obtained using phase unwrapping technique. Further, the effect of speckle size on the results is also discussed. © 2010 Copyright SPIE - The International Society for Optical Engineering.