Brightness and contrast corrections for space–time stereocorrelation via proper generalized decomposition

Stereocorrelation (SC) is a flexible, non-contact experimental tool for measuring 3D shape and surface kinematics in complex mechanical tests. The violation of gray level conservation raises the issue of convergence of SC (e.g., when local specular reflections are observed). Brightness and contrast corrections (BCCs) then become necessary. Space-time separation allows modes of the displacement, brightness, and contrast fields to be computed on the fly. The paper introduces a framework for Brightness and Contrast Corrections in Proper Generalized Decomposition stereocorrelation (BCCs-PGD-SC). It is shown that BCCs-PGD-SC improves the faithfulness of measured displacement fields and makes the identification of cracks viable from residual fields. The computational cost to include BCCs in PGD stereocorrelation is shown to be minimal within a PGD framework.