Single-aperture spatial phase-shifting technique for speckle shearography based on modified Michelson interferometer

Abstract

A modified Michelson interferometer for spatial phase shifting speckle shearography is presented. The interferometer consists of one slit aperture, one beam splitter, and two spherical mirrors. Spatial carrier frequency and shear are both generated by one translated spherical mirror. The slit aperture controls the speckle size. These arrangements make the system simple and easy to align. The shear is proportional to the translation of the spherical mirror. Shear distortion due to the rotated mirror in a traditional Michelson interferometer is avoided as well. The carrier frequency is proven to be constant in image plane and can be conveniently adjusted by translating the spherical mirror without changing imaging setup. Fourier analysis method is applied to accurately calibrate carrier frequency. Finally, experimental dynamic deformation results of a center loaded metal plate using the proposed method are provided.