Phase-based Full-field Displacement Measurement with Phase Nonlinearity Weighting Process

Abstract

The camera, as a non-contact sensor, has evolved into a robust tool for measuring the full-field vibration of complex structures. It offers distinct advantages over traditional contact sensors, including flexible positioning, simultaneous multi-point tracking, and high spatial resolution. Vibration imaging techniques have been developed to identify structural operational conditions through feature extraction methods. Phase-based vibration imaging techniques can visualize full-field operational shapes or vibrational features in a less-supervised manner. While phase-based optical flow with Gabor filters provides accurate displacement estimation, managing a large amount of image data can pose challenges in extracting full-field displacement efficiently. In this paper, we propose a compressive sensing approach for full-field phase-based optical flow and vibration imaging. Compressive sensing serves as an efficient sampling method that requires significantly fewer frames than traditional approaches, selecting frames at less than one third of the original video. Features are extracted from the displacement of the compressed video frames. Subsequently, the vibration features are transformed into images. The proposed methodology is validated through experiments conducted on an air compressor. Comparative results between vibration imaging from video with compressive sensing and that from the original video demonstrate that vibrational features can be extracted using only a few frames of the original video. Consequently, this approach can reduce processing time and data volume while preserving the performance of vibration feature extraction.