Noncontact Young's Modulus Measurement Using a Laser Interferometry–Digital Microscopy System: From Manganese Steel to Polylactic Acid Composites

High‐precision measurement of Young's modulus is essential for evaluating the mechanical properties of materials, yet traditional methods often exhibit high error rates and system complexity. This study presents a noncontact, fully digital sensor system that integrates Lloyd's mirror interferometry with digital microscopy imaging. The system employs a uniaxial stretching device and a Lloyd's mirror optical path to capture real‐time interference fringe images, and utilizes a multi‐algorithm fusion framework for accurate fringe centerline positioning. A MATLAB‐based GUI enables one‐click automated data processing. Experimental results show that the system measures the Young's modulus of manganese steel wire as 2.004 × 100 GPa with a relative uncertainty of 1.36%, outperforming CCD‐based methods (relative error > 4%). The Young's modulus measurements for pure aluminum wire, polylactic acid (PLA) composites, and aluminum alloy sheets are 0.776 × 100 GPa (relative uncertainty 2.63%), 3.016 × 100 GPa (relative uncertainty 1.19%), and 0.729 × 100 GPa (relative uncertainty 4.21%), respectively. Overall, the proposed system is a promising solution with broad engineering applicability for high‐precision elastic property measurements under complex conditions owing to its applicability to both metallic and non‐metallic materials.