Laser paint removal monitoring based on time-resolved spectroscopy

Laser paint removal is a new cleaning technology with high efficiency. Dynamic monitoring and closed-loop control of the laser paint removal process are key to reducing the risk of metal substrate damage and to achieving the best cleaning. In this paper, the time-resolved characteristics of the elemental peaks in the laser-induced breakdown spectrum of paints and substrate were studied by using the combination of a monochromator (or a bandpass filter) and a photomultiplier tube (PMT) detector. The results show that the intensity of the elemental spectrum peak of the paint has a sudden drop while the intensity of the elemental spectrum peak of the substrate has a sudden increase when the paint is removed. The time-resolved signals can be fitted by double exponential functions, which are combinations of exponential functions with a longer and a shorter lifetime, respectively. The relative ratios of the coefficients of the shorter and longer lifetimes (A(short)/A(long)) at the wavelength correspond to the elements in paint increasing suddenly while decreasing suddenly at the wavelength correspond ing to the substrate. The intensity of the elemental spectrum peaks of paints and substrate and the ratio (A(short)/A(long)) can be used to monitor the laser paint removal process in real time to reduce the damage risk of the metal substrate and achieve the purpose of efficient cleaning with low cost. (C) 2019 Optical Society of America