Research On Technology Of Spatial Carrier Frequency Shearography

The Electronic Speckle Shearing Pattern Intefferometry (ESSPI) is a opticaldetective method for measuring micro deformation of rough surface, which has beenwidely used in nondestructive testing of materials. Presently, most of Shearographyequipments usually use the temporal phase stepping technique which needs to collectmulti interferograms before and after the deformation. This limits it can only beapplied to the static measurement. Spatial carrier technique is suitable for phasedynamic measurement, which only needs a single frame before and after thedeformation. In this paper we expanded the following aspects of work focuses on thespatial carrier shearing speckle interferometry techniques：1.We have studied the phase extraction techniques for spatial carrierinterferogram, and improved the algorithm which could be used for dynamicmeasurement, such as the classical Fourier transform method.2. We have studied the the basic principles and methods that can introducemodulated speckle pattern into the interferogram, which helped us extracting phasefrom a single frame. And We have designed a shear amount adjustable dual-aperturespatial carrier shearing interferometry system, and a4f imaging system was used tohelp expanding the view field.3.We also studied the methods to reduce the noise that impact phase extractionand phase unwrapping, which had been compared and selected for dynamicmeasurement. And an interferogram acquisition and processing software wasdeveloped.4.In experiment we measured the dynamic changes in the surface of the rubberplate.The experiments show that the design of the spatial carrier shearing speckleinterferometry system can actually be applied to the dynamic deformationmeasurements.