Fig. 1. Principle diagram of Magneto-optical Imaging（MOI） detection for welding defects

Fig. 2. Distribution of magnetic induction lines in 3D finite element model of welding defects

Fig. 3. Distribution of magnetic induction intensity of leakage field in Z direction of pit

Fig. 4. Three-dimensional leakage field strength information in Z direction of surface pit

Fig. 5. Pit defect and its magneto-optic image

Fig. 6. Left edge information extraction of MOI of pit

Fig. 7. Two-dimensional plane profile of pit defect

Fig. 8. Valid value distribution in ROI

Fig. 9. Gradient variation of ROI in pit defect MOI

Fig. 10. Contrast of two kinds of 3D models of pit defect