SEA-RAFT-DIC: displacement-field measurement under degraded speckle conditions based on a laplacian probability distribution

Abstract

Digital image correlation (DIC) is widely used for full-field displacement measurement, but image degradation caused by occlusion, texture blurring, and speckle contamination, as well as rapid local correspondence variations induced by high displacement gradients and nonuniform deformation, can lead to matching failures and error amplification. Conventional DIC is constrained by the trade-off between spatial resolution and robustness, while existing deep learning-based methods generally lack explicit correspondence modeling and uncertainty constraints. To address these limitations, this study proposes SEA-RAFT-DIC, a DIC-oriented framework based on the global correlation and iterative update mechanisms of SEA-RAFT. A two-layer SmallStem, squeeze-and-excitation channel attention, and atrous spatial pyramid pooling are incorporated into the feature encoder to enhance local speckle details, informative channel responses, and multiscale displacement representation. A Mixture-of-Laplace Gradient Consistency Loss combines a mixture-of-Laplace probabilistic term, average endpoint error, and displacement-gradient consistency to model matching uncertainty while preserving displacement accuracy and structural continuity. A Hermite displacement-field speckle dataset and three degraded test sets containing occlusion, blurred textures, and salt-and-pepper noise are constructed. SEA-RAFT-DIC shows strong generalization even without degradation augmentation. After unified degradation-augmentation training, the full-field AEE values on the three test sets decrease to 0.2035 (occlusion), 0.1759 (blurred textures), and 0.1489 (salt-and-pepper noise), respectively, while the corresponding degraded-region values are 0.7953 (occlusion), 0.5343 (blurred textures), and 0.2748 (salt-and-pepper noise). A tensile experiment on a silicone plate with a prefabricated crack further demonstrates that SEA-RAFT-DIC is applicable to real high-displacement-gradient fields near crack tips and achieves favorable measurement accuracy, robustness, and practical potential under degraded speckle and complex deformation conditions.