Lasers
Laser Glossary of Terms
Accessible Exposure Limit (AEL) - Is the maximum permissible power level for the appropriate class of laser as defined in ANSI Z136.1.
American National Standards Institute, ANSI Z136.1 "Safe Use of Lasers" - This standard establishes occupational exposure limits and laser safety practices in the United States.
Aperture - An opening through which laser radiation can pass.
Aversion response - Closing the eye and moving the head away to avoid exposure to laser light.
Continuous Wave (CW) Laser - A laser with a continuous output of laser radiation for a duration that is greater than or equal to 0.25 seconds.
Diffuse Reflection - When a laser beam is reflected in many directions by a surface reducing its intensity.
Infrared Radiation (IR) - This is invisible radiation of wavelengths from 700nm - 1mm. This part of the electromagnetic spectrum is broken down into 3 bands: Near Infrared (IR-A) 700nm - 1400nm, Mid Infrared (IR-B) 1400nm - 3,000nm, and Far Infrared (IR-C) 3,000nm - 1mm.
Intrabeam Viewing - Direct viewing of a point source laser beam on axis.
Irradiance - The power per unit area expressed in watts per square centimeter (W/cm2). It is also referred to as power density and applies to CW lasers.
Laser - An acronym for "Light Amplification by Stimulated Emission of Radiation". A laser is a monochromatic (same wavelength), coherent (waves in phase), beam of radiation.
Laser Safety Officer (LSO) - The LSO is responsible for monitoring the control of laser use and implementing the Laser Safety Program.
Maximum Permissible Exposure (MPE) - The maximum level of laser radiation to which a human can be exposed without harmful effects to the eye or skin. MPE values for eye exposure to direct beam viewing can be found in Table 5 of ANSI Z136.1 standard.
Nominal Hazard Zone (NHZ) - An area where the MPE is exceeded for the laser radiation emitted.
Optical Density (OD) - Is the base ten logarithm of the reciprocal of the transmittance. The OD is calculated for protective eyewear to reduce the transmission density to the safe MPE level.
Pulsed Laser - A laser that delivers energy in single or multiple pulses which are less than or equal to 0.25 seconds in duration.
Radiant Exposure - Radiant energy per unit area expressed in joules per square centimeter (J/cm2). Radiant exposure applies to pulsed lasers.
Specular Reflection - Is a mirror-like reflection of the beam in which most of the power is retained in the reflected beam.
Ultraviolet Radiation (UV) - Invisible radiation that has wavelengths from 180nm - 400nm. UV radiation is broken down into 3 regions; Near Ultraviolet (UV-A)-315nm - 400nm, Mid Ultraviolet (UV-B)-280nm - 315nm, and Far Ultraviolet (UV-C)-100nm - 280nm.
Visible Radiation - Is radiation that is visible to the human eye. The wavelengths are from 400nm - 700nm. At these wavelengths the eye can focus the light onto the retina increasing the radiant exposure by 100,000 times.
Wavelength - The distance between two successive points on a periodic wave which have the same phase.
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