Brightness and contrast corrections for stereocorrelation: Global and instantaneous formulation with spatial regularization

Stereocorrelation (SC) is a versatile experimental method increasingly used to measure 3D surface displacements in complex mechanical tests. However, convergence issues may arise when gray-level conservation is no longer validated, particularly when local specular reflections are observed. Brightness and contrast corrections (BCCs) are added to the Global Stereocorrelation framework, including different spatial regularization strategies. A challenging experimental test case was chosen for validation purposes where extreme brightness and contrast changes were observed. An impact test on laminated glass was monitored with two high-speed cameras. It is shown that BCCs significantly improve the robustness and convergence rate for both calibration and kinematic measurements. Moreover, the numerical implementation cost into a finite element stereocorrelation code is negligible.