Simultaneous measurement of six displacement gradients using Digital Shearography

•The paper presents a method for achieving synchronized single-shot measurement of all six components of deformation derivatives utilizing a single color camera.•Different illumination configurations can be used to achieve equivalent and specialized measurement sensitivities to match different application scenarios.•Different Digital Shearography light path configurations can be respectively employed for higher precision or greater compactness. Optical methods show significant promise in accurately measuring all components of the displacement gradient tensor in three-dimensional space, excluding those related to depth measurement. However, dynamic measurements using Digital Shearography face challenges due to the complexity of acquiring sufficient phase information in one capture. This paper introduces a novel Digital Shearography system with triple beams and spatial phase shift capabilities. It allows simultaneous measurement of in-plane and out-of-plane phase distributions in a single image. Three laser beams, each with distinct wavelengths, are strategically positioned both horizontally and vertically to illuminate the object under test. Utilizing beam splitting and redirection, the system achieves dual shearing directions and captures shearograms using a 3CCD camera. Phase information extracted via the spatial phase-shift method enables determination of the six measurable displacement gradients and corresponding strain components. The manuscript provides a comprehensive explanation of the system’s theory, supported by experimental results, and explores potential applications.