Research progress of laser cleaning monitoring technology (invited)
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摘要: 激光清洗技术具有非接触、精度高、对基材损伤小、绿色环保等众多优点,在智能制造中发挥越来越重要的作用。随着激光清洗技术的发展,对激光清洗质量的快速检测及精准评价的需求越来越迫切。在激光清洗过程中,激光与待清洗层、基底发生作用,通过采集分析激光与物质相互作用过程中产生的光、声等信号和表面特性变化,可以实现对清洗过程和清洗效果的实时表征,完成对激光清洗的监控,目前逐渐被广泛地应用到自动化激光精密清洗过程中。文中分析和总结了声波监测法、光谱监测法和图像监测法等激光清洗监测技术的工作原理及研究进展,展望了激光清洗监测技术的未来发展趋势。Abstract: Laser cleaning technology has many advantages, such as non-contact, high cleaning accuracy, minor damage to the substrate, and being environmentally friendly. It plays an increasingly important role in intelligent manufacturing. With the development of laser cleaning technology, the need for rapid detection and accurate evaluation of laser cleaning quality is becoming increasingly urgent. The laser interacts with the layer to be cleaned and the substrate during laser cleaning. By collecting and analyzing the light, sound, and other signals and surface characteristics changes during the interaction between laser and substance, real-time characterization of the cleaning process and results can be realized, which is gradually widely used in the automated laser precision cleaning process. This review summarizes the working principle and research progress of laser cleaning monitoring technologies such as acoustic wave monitoring, spectral, and image monitoring. The possible future development and trend of laser cleaning monitoring technology are also discussed.
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Key words:
- laser cleaning /
- monitoring technology /
- research progress
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图 4 (a) 激光去除大理石上涂鸦的监测实验装置示意图;(b)涂鸦消融、有效清洁和基板损伤开始时的辐照区域的扫描电镜图像; (c)平均归一化PA信号与激光能流密度关系;(d)不同激光能流密度下归一化PA信号随脉冲数变化[13]
Figure 4. (a) Schematic diagram of the monitoring experimental setup of using laser to remove graffiti on marble; (b) SEM images of the irradiated areas at the onset of graffiti ablation, effective cleaning and substrate damage; (c) Relationship between the average normalized PA signal and the laser energy flow density; (d) The normalized PA signal changes with the number of pulses at different laser fluences[13]
图 6 (a)油漆经第一、第四、第六和第九次脉冲照射后的表面形貌;(b)不同作用脉冲数的时域信号;(c)声信号的频域波形;(d)频域信号随作用脉冲数量的变化;(e) LSD随脉冲数的变化[20]
Figure 6. (a) Surface topography of the paint after the first, fourth, sixth and ninth pulse irradiation; (b) Time-domain signals with different number of acting pulses; (c) Frequency domain waveform of the acoustic signal; (d) The change of frequency domain signal with the number of acting pulses; (e) LSD varies with the number of pulses[20]
图 10 (a)不同激光脉冲数作用油漆样品时375.9 nm (Ti)处的(0.5~1.2 µs)信号随时间演变;(b)~(i)不同激光脉冲数作用油漆样品之后,Ti元素在375.9 nm处的信号时间演变图[41]
Figure 10. (a) Evolution of (0.5-1.2 μs) signals at 375.9 nm (Ti) when different laser pulses act on paint over time; (b)-(i) Evolution of signals at 375.9 nm (Ti) after different laser pulses act on the paint sample[41]
图 11 经(a)三个、(b)四个和(c)五个激光脉冲照射后的表面形貌;(d) 第三、(e)第四和(f)第五脉冲作用时365.8 nm处的TRS信号;(g) 368.5 nm (Ti)处的TRS信号;(h) TRS 信号的强度与脉冲数的比值(0.3 μs); (i) TRS信号拟合系数的比值 (Ashort/Along) 随作用脉冲数的变化情况[42]
Figure 11. Surface morphology of the thin blue paint after being irradiated by (a) three, (b) four, and (c) five laser pulses; TRS signal at 368.5 nm and its double exponential function fitting (solid line) of (d) third, (e) fourth, and (f) fifth pulses on thin blue paint and substrate (black dotted line); (g) Detailed TRS signal at 368.5 nm (Ti); (h) Intensity of the TRS signal versus pulse number at 0.3 µs; (i) Ratio of the coefficient (
Ashort/Along) of the TRS signal of blue paint as a function of pulse numbers[42] 12 (a)用于激光清洗表面监测和过程诊断的反射光光谱监测装置示意图;(b)色度随辐照激光脉冲数的变化;(c)辐照不同脉冲数下的特征值及(d)污染表面、清洁表面和损伤表面的特征值;(e)在主要波长和能级的X-Y平面坐标系中的污染表面、清洁表面和损伤表面的特征值;(f)清洁表面和损伤表面的显微照片[44]
12. (a) Schematic diagram of a reflected light spectroscopy monitoring device for laser cleaning surface monitoring and process diagnostics; (b) The change of chromaticity with the number of irradiated laser pulses; (c) Characteristic values at different pulse numbers of irradiation and (d) Characteristic values of contaminated, cleaned and damaged surfaces; (e) Characteristic values of contaminated, cleaned and damaged surfaces in the X-Y plane coordinate system of the main wavelengths and energy levels; (f) Micrographs of cleaned and damaged surfaces[44]
图 13 (a)反射光信号功率测量装置;(b)不同功率密度和脉冲数下的反射光功率变化曲线[45];(c)用于涂层去除在线监测的He-Ne激光反射光信号功率测量系统装置;(d)不同能量密度和每点脉冲数下的反射光功率变化曲线[46]
Figure 13. (a) Reflected light signal power measuring device; (b) Reflected optical power variation curves at different power densities and pulse numbers[45]; (c) Schematic diagram of He-Ne laser reflected optical signal power measurement system device for online monitoring of coating removal; (d) Reflected optical power change curve under different power densities and pulses per point[46]
图 16 (a)在湿壁画上通过使用Nd:YAG激光器LQS、SFR模式和化学药膏(CH)清洁后得到的结果图;(b)不同清洁步骤测得的对应OCT扫描图(2 cm长)[57]
Figure 16. (a) Plot of results obtained by following the cleaning steps using the Nd:YAG laser LQS, SFR mode and chemical ointment (CH) on the fresco; (b) Corresponding OCT scanning plot (2 cm length) measured by different cleaning steps[57]
图 20 (a)进行FORS测量的13个点区域,激光处理过的区域(红色点)和未清洁区域(黄色点);(b) FORS获得的四种Vis-NIR反射光谱;(c)石膏的参考反射光谱;(d)~(e)在Vis光谱范围(420~885 nm)和在NIR光谱范围(1300~1615 nm)的伪彩色RGB图;(f)适用于950~1650 nm范围的光谱角映射器(SAM)分类图;(g)从HSI数据重建的RGB图像用于与图直接比较以及处理和未处理区域的视觉定位[56]
Figure 20. (a) 13 point areas where the FORS measurement was made, laser-treated areas (red dots) and uncleaned areas (yellow dots); (b) Four Vis-NIR reflectance spectra obtained by FORS; (c) Reference reflectance spectrum of gypsum; (d)-(e) Pseudo-color RGB plots in the Vis spectral range (420-885 nm) and NIR spectral range (1300-1615 nm), respectively; (f) Spectral angle mapper (SAM) classification plot for the 950-1650 nm range; (g) RGB images reconstructed from HSI data are used for direct comparison with plots and visual localization of processed and untreated areas[56]
图 21 (a)清洗装置示意图和实物图;(b)基于过程监控方法的钢板样品表面激光清洗前后对比;(c)锈蚀层3D形貌;(d)清洗后3D形貌[65]
Figure 21. (a) Schematic diagram and physical diagram of the cleaning device; (b) Comparison before and after laser cleaning of the surface of the steel plate sample based on the process monitoring method; (c) 3D morphology of the rust layer; (d) 3D morphology after cleaning[65]
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