Fig. 1. Principle of chromatic confocal measurement technology^[11-12]. (a) The structure based on pinhole and beamsplitter; (b) the structure based on Y-type fiber

Fig. 2. Linear dispersion lens group^[18]

Fig. 3. Dispersion objectives for commercial lens combinations^[20]

Fig. 4. Dispersion tube lens with large dispersion range^[21]

Fig. 5. Four cascaded dispersion objectives^[23]

Fig. 6. Dual light source chromatic confocal measurement system^[24]

Fig. 7. Reverse dispersion method^[25]

Fig. 8. Dispersion of ROE and DOE. (a) Refracting Optical Element; (b) diffractive Optical Element

Fig. 9. Miniaturized chromatic confocal point sensor with a diameter smaller than 2 mm^[33]

Fig. 10. Chromatic confocal measurement system based on FZP^[38]. (a) FZP; (b) measurement system

Fig. 11. Dispersion of hybrid lens and pure diffractive lens^[12]. (a) Hybrid aspheric diffractive; (b) pure lens diffractive

Fig. 12. Chromatic confocal measurement system based on supercontinuum light source^[47]

Fig. 13. Swept-source-based chromatic confocal measurement system^[51]

Fig. 14. The confocal spectrum measured by the spectrometer^[20]. (a) Spectral distribution of measurement signal with uniform power white light; (b) spectral distribution of measurement signal with white LED

Fig. 15. SPD characteristics of different light sources. (a) SPD of tungsten halogen lamps^[52]; (b) SPD of xenon lamp^[53]; (c) SPD of white LED^[54]; (d) SPD of supercontinuum light sources^[55]

Fig. 16. Advanced light source technology. (a) Laser driven light source^[56]; (b) Sunlike full spectrum LED^[57]

Fig. 17. Spectral power distribution tunable light source^[58]

Fig. 18. Three typical optical path structures of optical fiber spectrometer. (a) Crossed-asymmetric Czerny-Turner spectrometer; (b) symmetric Czerny-Turner spectrometer; (c) L-G-L spectrometer

Fig. 19. Structure based on lens and reflection grating^[20]

Fig. 20. Lens and transmission grating spectrometer^[72]

Fig. 21. Double dispersion imaging spectrometer^[73]

Fig. 22. C-T spectrometer with cylindrical lens^[74]

Fig. 23. Improved C-T spectrometer structure^[78]

Fig. 24. Multi-field spectrometer^[79]

Fig. 25. C-T spectrometer with hemispherical lens^[80]

Fig. 26. C-T spectrometer with convex lens^[81]

Fig. 27. Ultrathin spectrometer^[82]

Fig. 28. Spectral detection devices. (a) Based on spectral transmittance^[44]; (c) based on the differential ratio of two CCD signals^[83]

Fig. 29. Chromatic confocal measurement system with reference spectrum^[67]

Fig. 30. Chromatic confocal system based on slit aperture^[95]

Fig. 31. The type of spatial filter. (a) Slit; (b) pinhole array; (c) optical fiber array^[97]

Fig. 32. Multi-point scanning system based on conjugate fiber bundles^[98]

Fig. 33. Structure of line scanning chromatic confocal based on cylindrical mirror^[99]

Fig. 34. Beam mobile scanning system based on double galvanometer^[69]

Fig. 35. Beam mobile scanning system based on steering mirror^[103]

Fig. 36. Galvanometer scanning full field chromatic confocal system^[70]

Fig. 37. Chromatic confocal three-point sensor^[104]. (a) Structure diagram; (b) layout of segmented diffraction elements

Fig. 38. 3D scanning system installation diagram. (a) Based on microlens array^[107]; (b) microlens-based turntables^[108]

Fig. 39. Dot matrix scanning system based on single pinhole array^[113]

Fig. 40. DMD-based lateral scanning system^[118]. (a) Schematic diagram of the system; (b) scanning floor plan

Fig. 41. Chromatic confocal scanning system with LCD panel^[119]

Fig. 42. Chromatic confocal system based on DMD^[120]. (a) System diagram; (b) DMD projection pattern

Fig. 43. Different types of objective light path^[71]. (a) Non-flat field non-telecentric objective; (b) flat-field non-telecentric objective; (c) flat-field telecentric objective

Fig. 44. CCT system based on concave grating^[126]

Fig. 45. CCT system based on refraction and diffraction elements^[128]

Fig. 46. Biaxial chromatic confocal system for inclined illumination^[130]

Fig. 47. Area array spectrometer^[100]

Fig. 48. Double pinhole hyperspectral camera^[132]

Fig. 49. Double Amici prism^[119]

Fig. 50. Conversion of RGB to HSI^[131]