Fig. 1. Schematic diagram of the Nayar reflection model

Fig. 2. Schematic diagram of the dark-field illumination of mirror-like plane

Fig. 3. Schematic diagram of the dark-field illumination of mirror-like surface

Fig. 4. Schematic diagram of the PMD

Fig. 5. Image to be measured

Fig. 6. Average gray scale of 4 phase-shifted images

Fig. 7. Average curve of gray projection. (a) Horizontal projection curve; (b) vertical projection curve

Fig. 8. Average differential curve of the gray projection. (a) Horizontal projection curve; (b) vertical projection curve

Fig. 9. Interception results of the area to be measured

Fig. 10. Absolute phase difference diagram

Fig. 11. Result of the frequency domain processing

Fig. 12. Defect area

Fig. 13. Parts to be measured

Fig. 14. Imaging results of different methods. (a) Traditional way; (b) sine structured light

Fig. 15. Physical image of the detection device

Fig. 16. Detection results of multiple defects. (a) Scratch; (b) smudge; (c) hair; (d) bruise; (e) bump