Shearography technology and applications: a review

Abstract

Shearography is a full-field speckle interferometric technique used to determine surface displacement derivatives. For an interferometric technique, shearography is particularly resilient to environmental disturbances and has hence become an invaluable measurement tool outside of the optics laboratory. Furthermore, the inclusion of additional measurement channels has turned shearography from a qualitative inspection tool into a system suitable for quantitative surface strain measurement. In this review article we present a comprehensive overview of the technique, describing the principle of operation, optical configurations, image processing algorithms and applications, with a focus on more recent technological advances.

Development of the 3D Shape Shearography Technique for Strain Inspection of Curved Objects

“…Conventional shearography: capturing phase shifted interferograms before and after the object deformation, phase change obtaining and processing (incl. filtering, 2D unwrapping and zero order fringe tracking) [2,3]. 4.…”

“…Shearography (speckle pattern shearing interferometry) is a coherent-optical inspection technique [1,2] often used for non-destructive testing (NDT) and strain measurement [2,3]. Being an imaging technique, shearography provides full field measurements in a non-contact way.…”

“…Being an imaging technique, shearography provides full field measurements in a non-contact way. Shearography directly measures the surface displacement gradients which give a quantitative estimate of in-and out-of-plane surface strain components [2,3]. Six surface strain components, including in-and out-of-plane components can be measured with known 3D shearography configurations (with three or more viewing or illumination directions) [3,4].…”

“…Mostly flat objects at a known distance were inspected before [2,3]. In case of a flat object the data processing procedure can be significantly simplified and processing can be done in a "2D manner".…”

Phase discontinuity predictions using a machine-learning trained kernel

“…Shearography [2], for instance, is an effective interferometric speckle technique [3] that is well suited for the direct measurement of strain components in a nondestructive setting [4], and continues to be a fertile field of research in this domain [5]. Images produced by an interferometric speckle capture system are inherently noisy.…”