Synchronous Measurement of Out-of-Plane Displacement and Slopes by Triple-Optical-Path Digital Speckle Pattern Interferometry

This study proposes a triple-optical-path digital speckle pattern interferometry (DSPI) setup for measuring the full-field out-of-plane displacement and two orthogonal slopes simultaneously as well as independently. The designed setup contains one conventional out-of-plane speckle interferometer and two orthogonal modified shearographic interferometers with dual-observation geometry. In the setup, one laser device is used as the coherent source, and three monochrome cameras placed along a single line are used as the image acquisition device. Three correlation fringe patterns, one out-of-plane displacement fringe pattern and two slope fringe patterns, are captured synchronously by three cameras, and then are analysed using the phase-shifting technique to extract the phase distributions. The examinations of a practical non-contact measurement and a non-destructive testing (NDT) application by using the proposed setup are carried out in this study.