Characterization of a digital Image Correlation system for small biological tissues dynamic strain measurements

Digital image correlation (DIC) is an optical technique for contactless displacement and strain measurement recently applied to biological tissues. We characterized a DIC system for small biological specimens based on a high speed camera, a stereomicroscope, and an original image correlation algorithm. Optical features have been evaluated calculating the optical distortion and the modulation transfer function. The accuracy of the DIC algorithm used here has been assessed employing an elastic specimen subjected to known amount of strains, and has been compared with accuracies obtained in the same way using two other algorithms. For strain values up to 25%, that is within the typical strain range for biological tissues, and for magnifications up to 6.3×, our DIC algorithm was able to compute strains with a relative error lower than 1%. The accuracies obtained with the elastic specimen were then confirmed performing DIC analysis on mouse skin samples subjected to controlled strains.