A Lightweight DFT-Based Approach to the Optical Measurement of Displacements Using an Open-Source Python Code

• Published in: Experimental techniques (Westport, Conn.) Vol. 46; no. 3; pp. 485 - 496
• Main Authors: Nežerka, V., Havlásek, P.
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.06.2022
• Subjects: Characterization and Evaluation of Materials; Chemistry and Materials Science; Materials Science; Research Paper; Image analysis; Python programming; Motion tracking; Digital image correlation; Displacements
• ISSN: 0732-8818; 1747-1567
• DOI: 10.1007/s40799-021-00488-8

Commonly available digital image correlation (DIC) tools are designed to evaluate displacement/deformation fields using well-optimized correlation functions and computational procedures. However, real-time monitoring at high sampling rates or tracking motion at predefined locations from large sequence images can be hardly accomplished due to extreme computational costs. As shown in this paper, a lightweight approach based on the registration of subpixel subset shifts using discrete Fourier transform (DFT) can easily tackle large sets of images if the measurement is limited to discrete locations. A simple open-source python software designed for evaluation of displacements using virtual extensometers is described in this paper, along with the analysis of its performance. It is shown that the DFT-based algorithms outperform a commonly used DIC package in terms of computational efficiency and required user interactions, without sacrificing precision and accuracy.