Fig. 1. Principle diagram of triangulation survey

Fig. 2. Twelve-step sine phase-shift diagram

Fig. 3. Variation in wrapped phase and absolute phase with X-axis pixel

Fig. 4. Fringe pattern with four-bit Gray code

Fig. 5. Mapping diagram of different coordinate systems

Fig. 6. Fitting process of standard Lowess algorithm

Fig. 7. Fitting process of Robust Gaussian Lowess algorithm

Fig. 8. Functional diagram of measurement system

Fig. 9. Physical photograph of the measurement device

Fig. 10. Schematic diagram and physical photograph of measurement and control system

Fig. 11. Structure of OMU

Fig. 12. Physical photograph of HSDU

Fig. 13. 14 sets of calibration images

Fig. 14. CPU sample

Fig. 15. 3D point cloud of the sample surface

Fig. 16. Distribution of PV values for the sample surface over 50 measurement times

Fig. 17. Point clouds of the standard block surface. (a) Original point cloud; (b) point cloud after mapping depth

Fig. 18. Point clouds of standard block surface before and after fitting. (a) 3D view and (b) side view of Lowess fitting; (c) 3D view and (d) side view of Robust Gaussian Lowess fitting

Fig. 19. Fitted results of standard block surface by different methods. (a) Lowess fitting; (b) Robust Gaussian Lowess fitting

Fig. 20. Packaged chips

Fig. 21. Fitted chip surfaces by two algorithms under different temperatures. Fitted results by Lowess algorithm under (a) 50 ℃ and (b) 260 ℃; fitted results by Robust Gaussian Lowess algorithm under (c) 50 ℃ and (d) 260 ℃

Fig. 22. Variations in PV value of chip with temperature fitted by different algorithms