Determination of phase derivatives from a single fringe pattern using Teager Hilbert Huang transform

In this paper, a novel sequential algorithm for the estimation of phase derivatives from a single fringe pattern using electronic speckle pattern interferometry (ESPI) is proposed. The algorithm is based on empirical mode decomposition (EMD), vortex operator (VO) and Teager-Kaiser energy operator (TKEO). The empirical mode decomposition normalizes the fringe pattern; while vortex operator provides a 2D complex image and the phase derivatives are obtained using a novel image demodulation method called discrete higher order image demodulation algorithm (DHODA). Unlike phase shifting and Fourier transform methods, the proposed method does not require complex experimental setup or more than one fringe pattern for each deformation state. The proposed method is also able to provide phase derivatives in both thex andydirections from a single fringe pattern, which is difficult to achieve using shearography. Since the algorithm provides unwrapped phase derivatives directly, it does not require separate phase unwrapping process. Hence it is suitable for dynamic strain and curvature measurement. The proposed algorithm is validated by both simulation and experiment. The results are found to be accurate and the method requires less computation time than existing phase demodulation techniques.