This section has been reviewed and updated as needed: April 2014

Aversion Response
Closure of the eyelid, or movement of the head to avoid exposure to a bright light. The average response to an exposure from a bright laser source is assumed to occur within 0.25s, including the blink reflex time.
Controlled Area
An area where the occupancy and activity of those within is subject to control and supervision for the purpose of protection from radiation hazards. Examples of controlled area boundaries include: doors, curtains, and partitions.
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.
Maximum Permissible Exposure (MPE)
The level of laser radiation to which a person may be exposed without hazardous effect or adverse biological changes in the eye or skin.
Nominal Hazard Zone (NHZ)
The space within which the level of the direct, reflected, or scattered radiation during normal operation exceeds the applicable MPE. Exposure levels beyond the boundary of the NHZ are below the appropriate MPE level.
Laser
A device that emits a collimated (pencil-like) beam of either visible or invisible electromagnetic radiation (light). The acronym LASER stands for Light Amplification by Stimulated Emission of Radiation.
Laser System
An assembly of electrical, mechanical, and optical components which includes a laser.
Intrabeam Viewing
The viewing condition whereby the eye is exposed to all or part of a laser beam.
Specular Reflection
A mirror-like reflection.