What is distinction between Laser ClassⅠ and ClassⅡ ?

ClassⅠ Lasers are classified as inherently safe. Direct beam viewing, including with the use of optical aids, will not result in injury. Safety is achieved through engineering design and protective housing (for instance, a high-power laser source is fully contained, allowing only non-hazardous radiation leakage).

ClassⅡ Lasers are classified as conditionally safe. Their safety is dependent upon the natural aversive response (blink reflex) of the eye. While an inadvertent exposure is within safe limits, deliberate fixation on the beam presents a risk of retinal damage.