Grid-enhanced sampling moiré method for robust micro-deformation mapping under complex background noise

Accurate deformation field quantification in high-noise environments persists as a critical limitation for grid-based optical metrology. In this study, we develop a grid enhanced sampling moiré (GE-SM) method that enables robust microscale deformation mapping under complex background noise. This method employs Fourier-domain global periodic frequency extraction to isolate deformation-carrying grid signals from contaminating noise sources, achieving superior noise immunity compared to the traditional sampling moiré (SM) method. Detailed theoretical principles are presented, and numerical simulations verify that the GE-SM method can reduce the local errors from over 100% to within ±5% under simulated noise. Furthermore, carbon fiber reinforced plastic (CFRP) specimens in-situ heating experiments were performed, and the micro-scale thermal expansion strain field evolutions of this material at room temperature up to 130 °C were quantitatively characterized by the GE-SM method. The results confirmed that the GE-SM method can significantly reduce moiré phase disturbances and measurement errors induced by the complex fiber background, elucidating the distinct microscale thermal deformation behaviors of the resin and fiber in CFRP materials. The proposed method provides a promising solution for precise deformation retrieval in extreme noise scenarios, advancing capabilities in grid-based deformation measurement techniques.