The eyes and skin are the organs primarily at risk from exposure to laser light.
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The light produced by a laser has very different properties to that produced by other sources (such as the sun, light bulbs and fluorescent or neon tubes). Laser light is monochromatic (a single wavelength) and typically confined to a narrow beam which spreads only slightly with distance. Thus the energy carried by a laser beam is concentrated in a small area and can travel efficiently over large distances, giving laser radiation a far greater potential to cause injury than light from other sources.
In a ruby laser, light from the flash lamp, in what is called "optical pumping", excites the molecules in the ruby rod. Photons are emitted which bounce back and forth between two mirrors until coherent light escapes from the cavity.
Applications of laser technology are found in many fields including: medical, industrial (welding, cutting), construction, surveying, communications, entertainment, military and scientific research. Lasers are also found in many consumer items: laser pointers, barcode scanners, CD and DVD players and laser printers, for example. There are many different types of lasers usually distinguished by the lasing medium, some common examples are gas lasers: HeNe, Ar, Kr, CO2; solid-state lasers: Nd:YAG and semiconductors: laser diodes.
Lasers are classified according to the hazard associated with their emissions, as defined in the Australian/New Zealand Standard AS/NZS IEC 60825.1:2014 Safety of Laser Products Part 1: Equipment classification and requirements, AS/NZS IEC 60825.14:2011 Safety of Laser Products Part 14: A User's guide.
- Class 1 and 1M lasers are safe under reasonably foreseeable conditions of operation. Class 1M can be hazardous if the beam is viewed with Magnifying optical instruments (hence the letter ‘M’ is added).
- Class 2 and 2M lasers emit visible light at higher levels than Class 1, but eye protection is provided by aversion responses such as the human blink reflex. Class 2M lasers can be hazardous if the beam is viewed directly with magnifying optical instruments.
- Class 3R lasers produce visible and invisible light that are hazardous under direct viewing conditions. There is low risk for eye injury provided the exposure time is short. There is no risk for skin injury.
- Class 3B lasers produce visible or invisible light that is hazardous under direct viewing conditions; either they are powerful enough to cause eye damage in a time shorter than the human blink reflex (0.25 seconds) or the blink reflex is by-passed due to the invisibility of the beam. Laser products with power output near the upper range of Class 3B may also cause skin burns.
- Class 4 lasers are high power devices capable of causing both eye and skin burns, their diffuse reflections may also be hazardous and the beam may constitute a fire hazard.