Improvement of measuring accuracy of spatial fringe analysis method using only two speckle patterns in electronic speckle pattern interferometry

Abstract

High-resolution deformation measurement method, which requires only two speckle patterns in elec-tronic speckle pattern interferometry, is proposed by using fringe analysis based on specklegram. In fringe analy-sis using the proposed optical system, a pair of real-and imaginary-part components concerning the deformation information is extracted from one speckle pattern by Fourier transform in the same manner as the off-axis digital holography processing. A specklegram is calculated as a fringe image by multiplying the components of the real and imaginary part of speckle patterns in order to perform a high-resolution deformation analysis. Then, the phase map concerning deformation is detected from the specklegram, and the influence of speckle noise is also reduced by shifting the component on frequency domain. Furthermore, the amplitude of the intensity dis-tribution of speckle pattern is normalized in order to reduce the influence by speckle noise much more. It is confirmed that the accuracy of the deformation measurement is efficiently improved by the proposed noise reduction methods.