УДК 541.182 © B.G. Kukharenko ACTIVE CONTOUR MODEL FOR NONDESTRUCTIVE EVALUATION OF STRUCTURES USING SPECKLE INTERFEROMETRY Speckle interferometry - an electronic version of holographic interferometry - displays a shape of structural mode for the nondestructive evaluation of structure integrity. <...> Low-frequency preprocessing and histogram equalization enhance contrast and compensate equipment distortions, which are in the images displaying structural mode shapes. <...> The Independent Component Analysis of RGB-components of mode shape image as a whole produces contrast-enhanced shape images and gives an opportunity to extract its local features induced by cracks. <...> As shown, the crack edge is detected precisely enough by the active contour model. <...> Keywords: Nondestructive evaluation, structure integrity, Speckle interferometry, structural mode shape, image processing, Independent Component Analysis, active contour model. <...> ELECTRONIC SPECKLE PATTERN INTERFEROMETRY Electronic speckle pattern interferometry (ESPI) is laser-based technique used in non-destructive evaluation of structure integrity [1]. <...> The ESPI systems measure structural displacements and strains. <...> The structural image is formed in a video camera. <...> To obtain the holographic fringe pattern corresponding to the displacement field, two structural images (speckle patterns) are in need: one before deformation, and the other after deformation. <...> Subtraction of the two phases gives the interference phase change (fringe pattern) due to the structural deformation in numerical form. <...> A simple assumption is that the deformation field introduces change in the speckle phase of structural image only, leaving their amplitude unchanged. <...> In practice, however, there is also a small change in the speckle amplitude due to the structural deformation. <...> So, the displacement field can then be obtained by multiplying the interference phase map by the sensitivity constant of the ESPI system. <...> The strain field can be computed by differentiating the obtained displacement field [2]. <...> Note that Speckle interferometry technique is a relative measurement technique determining a phase change by module 2π and, hence, does not deliver absolute phase related to structural displacement. <...> However, knowledge of absolute phase is important for accurate determination of strains and stresses as well as for exact handling of the ESPI system. <...> Phase unwrapping corrects an apparent sharp transition of relative <...>