According to the laser beam’s MPE (maximal possible effect) of eyes, the laser is considered as ‘safe’ or not for intrabeam viewing, so lasers are generally classified and controlled according to the following criteria: Class I, Class II, Class III and Class IV.

Class I: low output laser (power less than 0.4mW), it is safe and visible regardless of any conditions, and it is safe to our eyes and skin. Looking at a Class I laser will not cause eye damage even where the entire beam enters the eye and it is being stared at continuously. Class I laser pointer includes such as laser printers.

Class II: low output and visible laser (power 0.4mW-1mW), won’t damage your eye if viewed momentarily. But usually the laser below 1mW will lead to dizziness and can not think. It is better that do not directly observe the intrabeam, and do not use Class II laser directly expose to other people’s eyes, avoid viewing the Class II by telescope. Class II laser pointer includes such as classroom demonstrations, laser pointer, aiming devices and range finder.

Class III: medium output laser beam, focused beam can injure the eye. Due to some security reasons, it can be further divided into Class IIIA and Class IIIB.

Class IIIA: visible continuous laser, the laser beam output is 1-5mW, the beam energy density should not exceed 25W/m-m, avoid using Telescopic equipment to view Class IIIA laser, and this may increase the risk. Class IIIA laser pointers have a lot in common with Class II laser pointers, such as laser pointer, laser scanners.

Class IIIB: 5-500mW continuous laser beam, it is dangerous to observe directly. The minimum irradiation distance is13cm and the maximum irradiation time are less than 10 seconds. Class IIIB laser is available in such as light shows and entertainment laser pointers.

Class IV: high-output continuous laser (greater than 500mW), higher than the Class IIIB, diffuse reflection is hazardous and/or a fire hazard. It will be used as the applications of surgery, research, cutting, welding and micro machining.