Two-dimensional structural motion estimation via analytical signal enhancement of phase-based video processing

Abstract

This paper concerns the use of phase information from image sequences for the extraction of structural two-directional motions. The phase-based motion estimation (PME) estimates local phase information via Gabor wavelet transform, and can only estimate the motion in single direction at a time, which will reduce the applicability and efficiency for many structures subject to more sophisticated bidirectional motions. This paper introduces a two-dimensional partial analytical signal to estimate the instantaneous phase and theoretically derives the relationship between the phase variations and the structure motion to achieve bidirectional motion estimations simultaneously. In addition to the analytical signal phase-based motion estimation (APME), this paper designs an ideal narrow-band filter (INF) addressing the limitation of the narrow frequency band in the analytical signals. In the proposed APME method, the acquisition of instantaneous phase improves the accuracy of structural bidirectional motion estimation. Moreover, the realization of the partial analytical signal is based on the fast Fourier transform (FFT) of the image and the dot product in the frequency domain, which bypasses the traditional PME convolution operation in the spatial domain. Therefore, the calculation efficiency of structural motion estimation is greatly improved. The proposed method is validated using a numerical simulation of a moving Gaussian surface with random motions. Results prove a good accuracy of the proposed APME method, and outperforming the traditional PME, the APME demonstrates an outstanding consistence to the true values (correlation coefficient 99.99%) four times better calculation efficiency. Further comparison with the experimental results of a cantilever beam also shows that the proposed method can better identify the structure bidirectional motion estimation.