Using Two-Beam Interferometry in Surface Deformation Monitoring Systems

Abstract

We consider the issues of expanding the range of measuring the shape and determining the deformation of a surface by wavefront detection methods such as holographic and speckle interferometry and speckle photography, based on a two-beam Jamin interferometer equipped with an image shifting device. A design has been developed for the two-beam interferometer with the device for shifting images in channels based on synchronously tilted plane-parallel plates. A technique for processing shear interferograms is decsribed. The accuracy of measuring the spacing of fringes in the interference pattern by Fourier-transform and wavelet-analysis based algorithms is studied. A block diagram of an automated device for interpreting speckle interferograms by the phase method based on a He–Ne laser in a magnetic field with a Zeeman frequency shift has been developed. It is shown that the accuracy of measuring the spacing of interference fringes can be as high as 0.02 of the interference fringe width.