Detection of internal defects using continuous wavelet transform and gradient streamlines in dual-channel speckle interferometry

A measurement method based on dual-channel speckle interferometry is proposed for the quantitative detection of internal defects in structures. The approach integrates digital speckle pattern interferometry and digital shearography (DS) to measure both out-of-plane displacement and its first-order derivative under single loading. On one hand, DS preliminarily evaluates defect boundaries, laying the foundation for subsequent defect boundary characterization. On the other hand, the combination of the continuous wavelet transform and the gradient streamline method enables complete boundary detection of hidden singularities in the out-of-plane displacement field. Finally, simulations and experiments demonstrate that the proposed method offers significant advantages in the detection of internal defects and the suppression of noise in speckle interferometry.