This article mainly introduces the classification of lasers and the hazard levels at different laser wavelengths.

The application of lasers has spread to many fields of scientific research, production, culture and education, and health, and the types of lasers used vary widely. In terms of output power, some are as high as 1012 to 1013 watts, and some are as low as 10-9 to 10-10 watts, and the difference is very large. Are such different lasers harmful to people? Some lasers, no matter how you use them, and whether you look directly into the laser beam or look through a high-powered magnifying glass, are not dangerous. Other lasers, as long as there is a very short pulse, hit any object in the laboratory, instead of being used and collected according to the predetermined design, the diffuse reflection laser alone can damage people’s eyes and skin. Therefore, when discussing the safe use and protective measures of lasers, the laser should first be classified according to whether it is dangerous or not, and different safety measures should be proposed according to different degrees of danger.

The parameters that determine the hazard level of a laser or laser system are mainly laser wavelength, output power density and maximum irradiation time of a continuous wave laser, and output energy density and irradiation time of a single-pulse laser. Generally, lasers are divided into 4 grades according to the damage to the eyes and skin according to the output level of the laser:

Harmless and control-free laser, its emission level is lower than the human eye safety standard value, and will not cause any harm to the human body.

Low-power lasers, whose continuous emission levels are less than 1 mW, allow the observer’s physiological reflex to avoid lasers with such low emission levels. However, if you look directly into the beam for a long time, it may cause retinal damage, but no damage to the skin.

Medium power lasers with emission levels ranging from 1 to 500 mW. In the human’s physiological light-avoidance reaction time, this light beam and its reflected light can damage the eyes, and high power and long-term exposure can cause damage to the skin. Such as He-Ne lasers.

High power lasers with emission levels greater than 0.5W on average. Its diffuse reflected light is enough to cause permanent damage to the human eye, and its direct-view beam can burn the skin. such as CO2 lasers.