Fig. 1. Schematic of mirror surface defect detection based on PMD

Fig. 2. Mirror surface defect detection system based on PMD

Fig. 3. Extraction of wrapped phase Φ(x,y). (a) Sequence image of four-step phase-shift; (b) wrapped phase Φ(x,y)

Fig. 4. Wrapped phase jump error. (a) Wrapped phase Φ(x,y) and corresponding a of jump error in some row; (b) local amplification of wrapped phase jump error

Fig. 5. Correction of wrapped phase jump error. (a) Wrapped phase with and without correction; (b) local amplification of wrapped phase correction effect

Fig. 6. Calculation of period index k(x,y). (a) Sequence image of Gray-code; (b) period index k(x,y)

Fig. 7. Unfolding of wrapped phase. (a) Wrapped phase Φ(x,y); (b) period index k(x,y) of wrapped phase; (c) absolute phase ?(x,y)

Fig. 8. Error in phase unwrapping. (a) Diagram of absolute phase intensity; (b) absolute phase of marked line in Fig. 8(a)

Fig. 9. Correction of period index k(x,y)

Fig. 10. Painted fuselage sample

Fig. 11. Diagram of experimental system

Fig. 12. Defect detection results without and with period index correction. (a)(b) Intensity images of absolute phase; absolute phases of marked line in (c) Fig. 12(a) and (d) Fig. 12(b); defect detection results in (e) Fig. 12(a) and (f) Fig. 12 (b)

Fig. 13. Defect locations and contours. (a) Defect locations and contours on wrapped phase image; (b) local amplification of defects

Fig. 14. Defect locations and contours on painted surface. (a) Hairy fiber; (b) sagging; (c) paint slag;(d) scratch before paint; (e) dirt; (f) dent; (g) craters; (h) bump