Abstract
Digital phase-stepping shearography is a speckle interferometric technique that uses laser speckles to generate the phase map of the displacement derivatives of a stressed object, and hence can map the stresses of a deformed object directly. Conventional digital phase-stepping shearography relies on the use of video cameras of relatively lower resolution, in the order of 5 megapixels or lower, operating at a video rate. In the present work, we propose a novel method of performing high spatial resolution phase stepping shearography. This method uses a 24 megapixel still digital imaging device (DSLR camera) and a Michelson-type shearing arrangement with an edge-clamped, center-loaded plate. Different phase-stepping algorithms were used, and all successfully generated shearograms. The system enabled extremely high-resolution phase maps to be generated from relatively large deformations applied to the test plate. Quantitative comparison of the maximum achieved spatial resolution is made with the video-rate cameras used in conventional shearography. By switching from conventional (video) imaging methods to still imaging methods, significantly higher spatial resolution (by about 5 times) can be achieved in actual phase-stepping shearography, which is of great usefulness in industrial non-destructive testing (NDT).
Highlights
Vijayakumar Anand, BoazDigital shearography, or digital phase-stepping shearography, has become an established interferometric tool in industry for measuring the whole-field deformation derivatives of test objects and for non-destructive testing [1,2,3,4,5,6]
We used the Nikon camera to generate most of the images in digital phase-stepping shearography
We first applied different amounts of central deformation to the test object, and we generated phase maps corresponding to each deformation
Summary
Digital phase-stepping shearography, has become an established interferometric tool in industry for measuring the whole-field deformation derivatives of test objects and for non-destructive testing [1,2,3,4,5,6]. In this technique, based on laser speckle interferometry, usually one of the mirrors in a sheared Michelson-type arrangement is moved by predetermined amounts to perform the necessary phase-stepping of the light beam, and capturing interference images of the test object at each step [1,2]. This limits the spatial resolution for the generated shearograms and phase maps and, limits the maximum value of the deformations that can be successfully observed
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
