Lens distortion correction for improving measurement accuracy of digital image correlation

Abstract

Digital image correlation is widely applied in the measurement of displacement and strain fields through detecting the laser or sprayed speckle on the specimen surface. Generally, the existing digital image correlation methods often met difficulties of low detection accuracy under the influence of lens distortion. To tackle such difficulties, the piecewise spline function is used to describe the distortion, and a continuous smooth distortion model can be obtained after eliminating the noises by means of the mean value filtering and smoothing spline algorithm. Since the proposed method corrects lens distortion on the pixel plane, it will provide opportunity to obtain unbiased displacement in digital image correlation. Experiment results verify that the proposed method eliminates the effect of lens distortion from displacements measurement by means of two-dimensional digital image correlation.