Digital Image Correlation (DIC)

Digital image correlation (DIC) is an optical non-contact technique to measure strains on surfaces. By using two cameras, one can obtain the three dimensional deformations (precision smaller than a pixelsize). High speed cameras can be used for transient deformations.

Some examples:

Strains on the upper beak of finches (left DIC, right computer model)

For a detailed description:

J. Soons, P. Lava, D. Debruyne, J.J.J. Dirckx, `Full-field optical deformation measurement in biomechanics: digital speckle pattern interferometry and 3D digital image correlation applied to bird beaks´, Journal of the Mechanical Behavior of Biomedical Materials, 14, 186-191, 2012.
http://dx.doi.org/doi:10.1016/j.jmbbm.2012.05.004