Fig. 1. System framework of image processing

Fig. 2. (a) Ordinary light source; (b) left structure light; (c) right structure light; (d) diagram of acquisition device

Fig. 3. Flow chart of defect area extraction

Fig. 4. (a) Raster stripe with break; (b) enlarged figure of fracture; (c) image after connection

Fig. 5. Template matching of the fifth grating stripes

Fig. 6. Distance of the fifth raster to template

Fig. 7. (a) Approximate area of defects; (b) intersection scatter plot; (c) Delaunay triangulation; (d) exact area of defects

Fig. 8. Different columnar sample defects. (a) Perforated magnetic sample; (b) solid magnetic sample; (c) aluminum column sample; (d) ceramic sample