Implementation and evaluation of optical flow methods for two-dimensional deformation measurement in comparison to digital image correlation

In experimental solid mechanics optical methods allow for non-contact derivation of full-field information. In this paper, optical flow based deformation measurement routines are implemented and compared to various commonly used digital image correlation procedures. The global Horn-Schunck and the local Lucas-Kanade optical flow method are utilized and adapted for large deformation measurement. Systematic tests with synthetic images are carried out for a detailed comparison of optical flow and correlation methods for varying subset sizes, noise levels, shape functions and gray level interpolations. The synthetic test data consists of rigid translation, different sinusoidal displacements and planar rotation. Within the study, the displacement calculation and the subsequent strain calculation are discussed and analyzed separately. Furthermore, the additive effect of measurement errors, when calculating with more than two successive images is investigated. Real experimental data is processed by all implemented methods and finally compared for validation and verification purposes.