The laser is divided into different types according to the wavelength, because the laser of different wavelength has different influence to the human tissues and organs. So in each type of laser according to its power output size and damage to the human body is divided into the following four.

The first class: laser harmless free control laser. This laser emission of this stage has no danger to human body in use, as well no damage the eyes. Free controlled the laser stage.

The second class: low power laser. Low output laser power, occasional look will not damage the eyes, but can not be a long time to look directly at the laser beam because retinal cells will be damaged by photons. But the laser does not have heat damage to the skin of the human body.

The third class: medium power laser. When this output power of the laser is focused, it will cause damage to the eye if you look directly, but when it change into none focusing, diffuse laser is generally not dangerous, this kind of laser has no heat damage to the skin.

The fourth class: high power lasers, such laser not only the direct beam and mirror reflective beam, eyes and skin will get damage seriously, and the diffuse light may also cause damage to the human eyes.