Principles and characteristics of Laser-Cleaning

The laser-cleaning is characterized by high directivity, monochromaticity, high coherence and high brightness. Through the focus of the lens and the Q switch, the energy can be concentrated into a small space and time range. In the laser-cleaning process, the following characteristics of the laser are mainly used:

1. The laser can achieve a high concentration of energy in time and space. The focused laser beam can generate thousands of degrees or even tens of thousands of degrees in the vicinity of the focal point, which can instantly evaporate, vaporize or decompose dirt.

2. The divergence angle of the laser beam is small and the directivity is good. The laser beam can be condensed into spots of different diameters through the condensing system. Under the condition of the same laser energy, controlling the laser beam spot with different diameters can adjust the energy density of the laser, so that the dirt will be heated and expanded. When the expansion force of the dirt is greater than the adsorption force of the dirt to the substrate, the dirt will be separated from the surface of the object.

3. The laser beam can generate ultrasonic waves on the solid surface to generate mechanical resonance and break the dirt off. Laser cleaning technology makes use of the characteristics of the above-mentioned laser to achieve the purpose of cleaning. According to the optical characteristics of the substrate material to be cleaned and the dirt to be cleaned, the laser cleaning mechanism can be divided into two categories:

One is to use the cleaning substrate (also called the matrix) and the surface attachment (dirt) to have a great difference in the absorption coefficient of a certain wavelength of laser energy. Most of the laser energy radiated to the surface is absorbed by the surface attachments, so that it is heated or vaporized and evaporated, or instantly expanded, and is driven by the formed airflow to separate from the surface of the object to achieve the purpose of cleaning.

Another type of cleaning method is suitable for cleaning the laser energy absorption coefficient of the substrate and the surface attachments, or the substrate is more sensitive to the acid vapor formed by the heating of the coating, or the coating will generate toxic substances after the heating.