Development of Speckle Interferometry for Simultaneous Dual Sensitive Measurement

Digital speckle interferometry involves two main methods: digital speckle pattern interferometry (DSPI/Digital Holography) and digital speckle pattern shear interferometry (Digital Shearography). This technology allows for non-destructive, full-field, high-precision measurements. In early stages, speckle interferometry was limited to measuring a single parameter in a single test, like in-plane or out-of-plane deformation or the first derivative of displacement (strain) along horizontal or vertical directions. However, advancements in speckle technology now allow simultaneous measurement of two of above parameters. These measurements systems, though, have limitations - they possess a single spatial resolution, resulting in certain drawbacks during deformation detection and non-destructive testing, such as difficulty in evaluating dense fringes or overlooking smaller defects. Recent advancements have led to a new study using digital shearography, measuring one parameter with two different spatial resolutions. However, due to its recent emergence, there's limited literature on this method. Both measuring two parameters with one spatial resolution and measuring one parameter with two spatial resolutions are referred to as dual-sensitive measurement. This study mainly concentrates on simultaneous measurement of target parameters using speckle pattern interferometry technology. It delves into two key areas: enhancing digital shearography to achieve dual parameters and dual spatial resolution measurements, and developing novel digital holography for dual spatial resolutions. The novel digital holography method employs different-sized fields of view and polarization techniques to establish independent optical channels. Unlike shearography systems, it uses spatial carrier phase-shifting technology to separate overlapped intensity maps. This method proves more convenient and practical than traditional methods by eliminating the need to adjust shear directions. Ultimately, this technique can simultaneously produce dual-sensitive measurement results at different spatial resolutions, reducing the need for redundant measurements and saving time and labor costs. With ongoing enhancements, this technology holds significant promise for industrial applications and interest researchers focused on experimental mechanics via speckle/holographic interferometry