Cross‐Correlation and Differential Technique Combination to Determine Displacement Fields |
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Authors: | A M R Sousa J Xavier M Vaz J J L Morais V M J Filipe |
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Affiliation: | 1. CITAB, Engineering Department, University of Trás‐os‐Montes and Alto Douro, 5001‐801 Vila Real, Portugal;2. Faculty of Engineering, University of Porto, Porto, Portugal |
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Abstract: | Abstract: This study presents a method to measure the displacement fields on the surface of planar objects with sub‐pixel resolution, by combining image correlation with a differential technique. First, a coarse approximation of the pixel level displacement is obtained by cross‐correlation (CC). Two consecutive images, taken before and after the application of a given deformation, are recursively split in sub‐images, and the CC coefficient is used as the similarity measure. Secondly, a fine approximation is performed to assess the sub‐pixel displacements by means of an optical flow method based on a differential technique. To validate the effectiveness and robustness of the proposed method, several numerical tests were carried out on computer‐generated images. Moreover, real images from a static test were also processed for estimating the displacement resolution. The results were compared with those obtained by a commercial digital image correlation code. Both methods showed similar and reliable results according to the proposed tests. |
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Keywords: | digital image correlation displacement fields optical flow sub‐pixel resolution |
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