From the method analysis, there are four laser cleaning methods:
①laser dry cleaning method, that is, the use of pulsed laser direct radiation decontamination;
②Laser liquid film method, that is, first deposit a layer of liquid film on the surface of the matrix, and then use laser radiation decontamination;
③Laser and inert gas method, that is, at the same time of laser radiation, with inert gas blown to the substrate surface, when the dirt from the surface will be immediately blown away from the surface, in order to avoid surface pollution and oxidation;
④Use laser to make dirt loose, and then clean with non-corrosive chemical methods. At present, the first three methods are commonly used. The fourth method is only found in the cleaning of stone artifacts.

Stone carvings and other ancient high-grade stone art, because of their extremely fine and fragile surface structure, become the earliest application of laser cleaning field. People have found that the use of laser to remove dirt on the surface of stone cultural relics has unique advantages. It can precisely control the migration of light beam on the complex surface to remove dirt without damaging the cultural relics and stones. For example, in September 1992, UNESCO's World Heritage Organization commemorated the 20th anniversary of its founding by carrying out a repair project to the famous Amiens Cathedral in the United Kingdom. The key to the project is the exquisite marble carving of the Virgin's Gate on the west side of Amiens Cathedral. In THE ONE-YEAR REPAIR PROJECT OF THE VIRGIN GATE, maintenance personnel with the help of laser, laser beam out a few millimeters thick layer of black scale covering the marble carving pattern, the original color of the marble surface is reflected, so that the exquisite carving luster. For example, the InsBrunthier stone collection, one of the most important stone sculpture collections in Britain, was laser-cleaned to achieve the same effect. People use electron microscope to observe the stone surface after laser cleaning, it is found that the structure of the stone after laser cleaning does not change, the cleaned surface is smooth and flat, no damage. This is completely different from the surface cleaned by the microparticle spraying (sandblasting) method. It is difficult to avoid the damage of marble surface structure after microparticle jet cleaning, especially for the marble surface with sulfate scale layer. Electron microscopy also found that the properties of the rock material under the surface were neither degraded nor changed after laser irradiation. At present, using laser to clean the dirt on the surface of high-grade stone materials such as limestone and marble has become a new promising business project.

In addition to the cleaning of stone materials, laser cleaning in glass, quartz, metal, mold, tooth, chip, electrode, magnetic head and disk as well as a variety of microelectronic products cleaning has a good effect, has been a certain application.

The prospect of laser cleaning
In the world, laser cleaning technology has been applied to stone materials for more than 10 years. In China, the laser cleaning of stone material has just started. Because the investment of laser equipment is still relatively expensive at present, it is difficult to generalize the application. However, laser cleaning technology has the advantages that traditional cleaning methods can not be compared with. With the continuous improvement of technology and the mass production of equipment, laser cleaning technology will play an important role in the cleaning industry of stone materials and has a good development prospect.