Influence of shearing direction on slope fringe distributions in the presence of in-plane displacement and strain components in double-aperture speckle shearing interferometry

Abstract

The influence of shearing direction on slope (first-order derivative of out-of-plane displacement component) fringe distributions in the presence of in-plane displacement and strain components in double-aperture speckle shearing interferometry is discussed in detail. The research results show: (1) only in-plane displacement component parallel to the centre line of double apertures influences slope fringe distributions; (2) in-plane strain components have no influence on slope fringe distributions if utilising normal illumination and an axisymmetric system; and (3) shearing direction has an important influence on slope fringe distributions in the presence of in-plane displacement and strain components. Theoretical analysis and experimental demonstrations are given. The experimental results are in good agreement with the quantitative analysis.