Quality analysis of DSPs with different edges in DIC-based deformation measurements

The digital speckle pattern (DSP) is one of the key factors in digital image correlation (DIC), and its quality directly determines the accuracy of the computations. In practical DIC calculations, factors such as non-uniform illumination and imaging system limitations result in nonlinear shifts in image gray-scale values and a reduction in contrast, thereby causing alterations in the actual edges. Therefore, it is essential to determine the optimal production parameters for DSPs based on edge conditions and to clarify the impact of these production parameters on the DSP quality. In this study, we generated DSPs with different edge types and combined sub-pixel and orthogonal experiments to obtain the optimal parameters under various edge conditions, thereby elucidating the influence of production parameters on the DSP quality. Furthermore, deformation tests were conducted using the optimal DSPs for different edge types, achieving effective measurements of up to 60% strain when using Gauss and complex edges. This study proposes a DIC measurement method based on DSP edges. Before fabricating the DSP, the actual DSP edge is determined by capturing a single speckle, after which the DSP production parameters are selected accordingly. Using this method, the average absolute calculation error in strain measurements can be reduced by up to 41.30% under underexposure conditions. This research provides theoretical guidance for generating DSPs for deformation measurements in specialized scenarios.