Digital speckle photography with correlation processing of spatial spectrum of specklegram for determination of micro displacement of scattering object

The method of digital speckle photography for determining of speckle pattern displacement with sub-pixel accuracy using correlation processing of summary spatial spectrum of speckle patterns is considered in this article. It is assumed that displacement of speckle pattern is caused by deformation or displacement of an object with a scattering surface. The method of phase shift of interference pattern in diffraction halo is proposed for expanding the lower limit of measuring range of speckle pattern displacement to subpixel values. The method is based on numerical additional phase shifts of complex spatial spectra of displacement and non-displacement speckle patterns. The results of numerical and natural experiments are presented.