Fig. 1. Chromatic confocal sensor applications. (a) Measurement of the inner diameter of workpieces; (b) panel gap measurement; (c) wafer defect detection; (d) welding quality measurement

Fig. 2. Range of performance parameters for selected commercial grade spot chromatic confocal sensors

Fig. 3. Schematic of point chromatic confocal system. (a) Schematic of the system principle; (b) structure of the system

Fig. 4. Light source of chromatic confocal system. (a) Super-continuous laser and its wavelength depth mapping^[14]; (b) SLD and its wavelength depth mapping^[18]

Fig. 5. Characteristics of various types of broad spectrum light sources

Fig. 6. Comparison of objective lenses with different NA regarding height and roughness measurements^[23]. (a) Comparison of measured height; (b) comparison of measured roughness

Fig. 7. Schematic of the thresholding peak extraction algorithm^[40]

Fig. 8. Relative deviation of each position under different peak wavelength extraction algorithms (2 μm step)^[42]

Fig. 9. Expectation value and standard deviation of the peak extraction errors of different algorithms^[45]

Fig. 10. Confocal scanning microscopy based on galvanometer^[53]. (a) Schematic of the principle; (b) system structure

Fig. 11. Confocal scanning microscopy based on acousto-optic deflectors. (a) Used alone^[56]; (b) used combined^[58]

Fig. 12. Line chromatic confocal microscopy. (a) Coaxial chromatic confocal system structure; (b) biaxial chromatic confocal scanning system structure

Fig. 13. Schematic of the dark-field line-scanning surface inspector^[65]

Fig. 14. Confocal scanning microscopy based on fiber bundle^[65]

Fig. 15. Confocal scanning microscopy based on microlens array^[80]

Fig. 16. Confocal scanning microscopy based on DMD^[84]