Evaluation of the impact of filter types and parameters upon the accuracy of phase-based optical flow method with a complex steerable pyramid

Complex steerable pyramid (CSP) performs well when applied to magnify subtle motions of structures for observing the dynamic characteristics of facilities. However, the impact of the types and parameters of CSP filters upon the performance of phase-based optical flow (PBOF) in measuring motion parameters has not been systematically studied. The purpose of this study is to comprehensively evaluate the impact of different CSP filter types (Octave, HalfOctave, SmoothHalfOctave, and QuarterOctave) and parameters on the performance of PBOF in measuring motion parameters. Firstly, by measuring simulated translational motion, the influence of the CSP's down-sampling rates on the displacement measurement accuracy of PBOF is analyzed to determine appropriate settings. Subsequently, the effective displacement measurement interval and accuracy of PBOF using the CSP are studied through simulated and experimental translational motion measurements. Further, the vibration parameter's accuracy is analyzed through simulated periodic vibration measurements. Finally, the characteristics of PBOF using the four kinds of CSP and practical considerations are discussed. Simulation and experimental results demonstrate that when using middle-level filters within the effective level range of HalfOctave, PBOF achieves the best overall displacement measurement performance. Additionally, this method can easily integrate with signal processing techniques in analyzing structural dynamic characteristics under field conditions.