Visual vibration measurement using intensity optical flow with optical field correction under uneven illumination

Abstract

The intensity optical flow method is widely used in vibration measurement due to its efficiency and low computational cost. However, its performance degrades significantly under uneven illumination, often resulting in distorted vibration mode shapes in full-field measurements. To address this issue, this study proposes a novel approach that incorporates an optical field correction model into the intensity-based optical flow framework. This is the first method to explicitly model the spatial relationship between illumination and vibration response, enabling one-shot correction of mode shape distortion using single-frame optical field estimation. Simulation results demonstrate that the proposed method achieves Modal Assurance Criterion (MAC) values above 0.95 under various complex lighting conditions and maintains values above 0.85 even in the presence of severe system noise. Compared to conventional dynamic correction techniques, it eliminates cumulative errors and significantly improves processing efficiency by avoiding frame-by-frame adjustments. Experimental validations on metal plates, air compressors, and gold-coated thin films further confirm the robustness and practical applicability of the method in real-world vibration measurement scenarios.