A:
Primary laser: A laser with a power less than 0.4 milliwatts, that is, a harmless and controllable laser. The laser emitted by this level of laser does not pose any danger to the human body when used, and even when viewed directly with the eyes, it will not harm the eyes. This type of laser does not require any control.
Secondary laser: refers to a low-power laser (with a power range of 0.4 milliwatts to 1 milliwatt). Although the output power of this level of laser is very low and occasional eye contact may not cause eye damage, it is not advisable to look directly at the laser beam for a long time. Otherwise, retinal cells will be damaged by the action of photons. But this type of laser does not cause thermal damage to human skin.
Third level laser: medium power laser (power between 1 milliwatt and 500 milliwatt). In terms of output power, such as focusing, this level of laser can cause eye damage when looking directly at the beam, but converting the light into non focused, diffuse reflected laser is generally not dangerous, and this type of laser does not cause thermal damage to the skin.
Fourth level laser: refers to a high-power laser (with a power greater than 500 milliwatts). The harm of this level of laser is not only that its direct beam and mirror reflection beam can cause serious damage to the eyes and skin, but also that its diffuse reflection light can cause damage to human eyes.
