Local digital image correlation algorithms: spatial domain versus frequency domain approach

Digital image correlation (DIC) is widespread in many research fields to achieve full-field displacement measurements. The main idea behind the DIC method is the computation of the correlation factor between image subsets before and after deformation to assess the rough displacement. The correlation map, which is computed at the pixel level, is then refined to subpixel accuracy through interpolation methods or non-linear optimization. The aim of this research is to develop two digital image correlation algorithms for vibration measurements. The first will be based on the conventional approach, which computes the correlation factor in the spatial domain by convoluting the pixel-wise grey levels to obtain the correlation map. The second will be based on the computation of the correlation factor in the frequency domain. The algorithms will be evaluated in terms of performance when applied to the same image set, by comparing the computational time, and the sensitivity to small amplitude values, which are typical of vibrations.