Synchronous Imaging and Multimodal Fusion of Optical and Electromagnetic Measurements for Overlapping Defects Inspection

It is a challenging problem to accurately detect overlapping defects. This paper proposes a system that can obtain optical and electromagnetic signals synchronously. It contains an industrial camera, a chromatic confocal displacement sensor (CCDS) and an eddy current testing (ECT) probe with high-resolution array tunneling magnetoresistance (TMR) sensors. A multimodal fusion algorithm is proposed to combine the advantages of the optical testing and ECT. The fusion of the visual image and CCDS measurement results in morphology of the surface defects. To recognize the overlapping buried defect, a finite element method model is developed to estimate the surface defect signal using parameters from the optical measurements, and then the surface defect signal is subtracted from the experimental image, based on which the overlapping defects are precisely detected. This method can be widely used in industry to comprehensively assess the health and integrity of structures.