Fig. 1. Development history of laser cleaning technology and equipment in China^[7-20]

Fig. 2. Cleaning methods and removal mechanisms for surface contaminants on typical components^[25-35]

Fig. 3. Laser cleaning effect and mechanisms of oxide film on surface of aviation titanium alloy inlet^[25-27]. (a) Surface morphologies of titanium alloy after cleaning; (b) main mechanism of laser dry cleaning of titanium alloy oxide film; (c) main mechanism of laser wet cleaning of titanium alloy oxide film

Fig. 4. Laser cleaning effect and mechanisms of paint on high-speed aluminum alloy car body surface^[28-29]. (a) Surface morphologies after aluminum alloy cleaning; (b) main mechanism of laser dry cleaning of blue/red paint on aluminum alloy surface

Fig. 5. Effect and mechanisms of laser cleaning of rust on high strength steel hull surface^[30-32]. (a) Surface morphologies of high strength steel after cleaning; (b) main mechanisms of laser dry/wet cleaning of surface rust on high strength steel hull

Fig. 6. Effect and mechanisms of laser cleaning of marine microorganisms on aluminum alloy surface^[33-35]. (a) Surface morphologies after aluminum alloy cleaning; (b) main mechanisms of laser dry cleaning of marine microorganisms on aluminum alloy surface

Fig. 7. Energy conversion model in laser cleaning process^[40]

Fig. 8. Finite element model of nanosecond pulse laser cleaning of TA15 titanium alloy oxide films^[40-41]. (a) Gaussian spot loading; (b) flat top spot loading

Fig. 9. Finite element model of nanosecond pulse laser cleaning of aluminum alloy marine film layer^[42-43]. (a) Contour traces after laser spot ablation; (b) analysis of edge features and contour depth

Fig. 10. Thermal stress curve of nanosecond pulse laser cleaning of titanium alloy oxide film。(a) Surface stress versus time under different single pulse powers; (b) stress versus distance under different powers; (c) stress versus distance under different surface depths

Fig. 11. Intensity of sound signals generated at each stage of laser paint removal process^[48]. (a) Surface morphologies of coatings after different pulse irradiations; (b) time-domain signals of 1‒20 pulses; (c) acoustic signal frequency domain waveforms; (d) signal intensities at different frequencies; (e) local standard deviations under different numbers of pulses

Fig. 12. Evaluation of laser cleaning of marble based on acoustic signals^[49]. (a) Laser assisted removal of black spray under different energy fluxes; (b) experimental configuration during photoacoustic measurement process; (c) evolution of typical normalized photoacoustic signal

Fig. 13. Real time monitoring system combining PA signal with high-resolution optical images^[50]. (a) Experimental configuration for on-line monitoring of laser cleaning; (b) evolution of mean PA amplitude of recorded signal for each wavelength; (c) optical images of laser spot

Fig. 14. Real-time surface particle identification method for laser cleaning based on imaging^[51]. (a) Cleaning efficiency versus laser pulse flux; (b) image of particles on carrier surface before cleaning; (c) image of particles on carrier surface after cleaning

Fig. 15. Detecting cleanliness of metal samples using LIBS technology during pulse laser cleaning process^[52]. (a) Schematic of real-time monitoring system for laser cleaning; (b) schematic of K-nearest neighbor relationship; (c) distribution of spectral peak

Fig. 16. 2D mapping element distribution maps based on LIBS during laser paint removal process^[53]. (a) Images of base metal, painted metal, and samples after laser cleaning; (b) LIBS of each sample; (c) backscattered electron (BSE) image and corresponding elemental distribution maps obtained from electron microprobe analysis (EMPA) for base metal; (d) BSE image and corresponding elemental distribution maps obtained from EMPA for paint

Fig. 17. Multivariate parameter online detection and control system based on spectroscopy. (a) Physical image; (b) schematic

Fig. 18. Laser cleaning morphology and diffuse reflection absorption spectrum of titanium alloy in each area. (a) Laser cleaning morphology of ​​titanium alloy in each area, where zone 1 is uncleaned area, zone 2 is insufficient cleaning area, zone 3 is clean area, and zone 4 is over cleaned area; (b) diffuse reflection absorption spectrum of titanium alloy in each area; (c) characterization of clean area of titanium alloy; (d) characterization of over-cleaned area of titanium alloy

Fig. 19. Online spectral detection of surface quality of high-strength steel after laser cleaning. (a) Spectral detection path; (b) σ_g value

Fig. 20. Online spectral detection of surface quality of aluminum alloy after laser cleaning. (a) Spectral detection path; (b) σ_g value

Fig. 21. Construction of deformation measurement system. (a) Image acquisition system; (b) measurement light source

Fig. 22. Domestic and foreign aerospace intelligent laser cleaning equipment^[55-58]. (a) RLCRS; (b) ARBSS; (c) LCR robot; (d) automation equipment

Fig. 23. Intelligent laser cleaning equipment for domestic and foreign rail transit^[59-60]. (a) Laser train; (b) “integrated cleaning and welding” equipment

Fig. 24. Intelligent laser cleaning equipment for ship manufacturing at home and abroad^[61-62]. (a) Underwater cleaning robot; (b) intelligent wall-climbing rust removal robot

Fig. 25. Method for shaping ultra-long line spot beams in multiple light source composite optical paths^[1]

Fig. 26. Ultra-long line spot efficient laser cleaning equipment of Harbin Institute of Technology ^[61] .(a) Ultra-long line spot efficient laser cleaning head based on multi-light source composite optical path; (b) galvanometer scanning ultra-long line spot efficient laser cleaning head; (c) application and equipment verification for efficient laser cleaning of high-speed rail and marine large components

Fig. 27. Intelligent flexible laser cleaning robot equipment of Harbin Institute of Technology ^[62-65]. (a) Cleaning trajectory motion unit; (b) integrated prototype of intelligent flexible cleaning robot equipment; (c) physical object of intelligent flexible cleaning robot equipment