Optical Motion Magnification: A Comparative Study and Application for Vibration Analysis

Optical motion magnification (OMM) is a non-contact monitoring technique that is gaining popularity in the vibration analysis and structural health monitoring (SHM) communities. Using ordinary video of a targeted structure, OMM algorithms can extract imperceptible motion and identify issues that may lead to structural failure. This technique can produce not only qualitative magnified videos revealing exaggerated displacements but also quantitative assessments of displacements from which frequency content can be obtained. The objective of this work is to investigate the performance of OMM as a vibration monitoring technique that has application for analysis of large-scale structures. Therefore, a comparative study between two commercially available OMM systems and one open-source algorithm is performed to determine the accuracy of those techniques compared to traditional contact-based measurements. Extensive laboratory tests performed on a structure oscillating at a known amplitude and frequency showed that OMM can measure displacements as low as three microns with 95% correlation in the time domain when compared to traditional contact-based sensing. An example of the potential of OMM to be a cost-effective, non-invasive, and quick condition monitoring technique for large structures (e.g., wind turbines and bridges) is discussed. By using OMM, the issues inherent in standard testing/monitoring procedures can be eliminated, allowing the time and cost of SHM to be significantly reduced.