accessible radiation - Laser radiation to which it is possible for the human eye or skin to be exposed in normal use.

authorized person - A person who has the approval of the area supervisor and/or program management to perform a particular function in that area.

aversion response - Movement of the eyelid or the head to avoid an exposure to a noxious stimulant or bright light. An aversion response is assumed to occur within 0.25 s, including the blink-reflex time.

continuous wave (CW) - A laser operating with a continuous output for >0.25 s.

controlled area - An area where the occupancy and activity of those within is subject to control and supervision for the purpose of protection from hazards.

diffuse reflection - Change of the spatial distribution of a beam of radiation when it is reflected in many directions by a surface or by a medium.

embedded laser - A laser with an assigned class number higher than the classification of the laser system in which it is incorporated, where the system’s lower classification is appropriate because of the engineering features limiting accessible emission.

irradiance (E) - Optical power per unit area reaching a surface (W/cm2).

joule (J) - A unit of energy (1 joule = 1 watt-second).

laser - A device that produces an intense, coherent, directional beam of light by stimulating electronic or molecular transitions to lower energy levels. An acronym for Light Amplification by Stimulated Emission of Radiation.

MPE - Maximum Permissible Exposure - The level of laser radiation to which a person may be exposed without hazardous effect or adverse biological changes in the eye or skin.

power - The rate at which energy is emitted, transferred, or received. Unit: watt.

pulsed laser - A laser that delivers its energy in the form of a single pulse or a train of pulses, with a pulse duration of <0.25 s.

radiant exposure (H) - Optical energy per unit area reaching a surface (Joules/cm2).

reflection - The deviation of radiation following incidence with a surface.

repetitively pulsed laser - A laser emitting multiple pulses of radiant energy occurring in a sequence with a pulse repetition frequency (PRF) 1 Hz or 1 pulse/s.

specular reflection - A mirror-like reflection.