High-performance digital shearography integrating spatial light modulator with micro-polarizer camera

Abstract

Digital shearography (DS), a laser-based optical interferometric method, is widely employed for measuring the first-order derivative of an object's surface deformation. Unlike digital holography, DS integrates self-reference optics, enhancing resistance to environmental disturbance and improving detection sensitivity, making it ideal for non-destructive testing (NDT). DS finds applications in diverse fields such as material inspection, fluid property research, medical diagnostics, cultural heritage restoration, and military defense. The conventional temporal phase-shift (TPS) method encounters limitations in dynamic tests, leading to the introduction of the spatial phase-shift (SPS) method. However, SPS is restricted by aperture size, impacting the phase map quality. The spatial light modulator (SLM) introduces a novel approach to DS system development, enabling quantitative shearing adjustments through precise SLM control. Existing DS systems using traditional phase-shift technology rely on interferometers and struggle to achieve high-quality phase maps with a single exposure. The proposed high-performance DS, leveraging both SLM and a micro-polarizer camera, overcomes this limitation, facilitates single-exposure phase map evaluation with the polarization phase-shift technique, and eliminates the need for a tiny aperture, enhancing light beam utilization and phase map quality.