American National Standards Institute (ANSI) - The technical body which releases the Z136.1 Standard for the Safe Use of Lasers and Z136.3 Standard for Safe Use of Lasers in Health Care Facilities. The secretariat for the Z136.X standard series is the Laser Institute of America.
Average Power - The average power of a pulsed laser is the product of the energy per pulse (J/pulse) and the pulse repetition frequency (Hz or pulses/sec). The average power is expressed in Watts (J/sec).
Aversion Response – Closure of the eyelid, eye movement, pupillary construction, or movement of the head to avoid exposure to noxious or bright light stimulant. The aversion response to an exposure from a bright, visible, laser source is assumed to limit the exposure of a specific retinal area to 0.25 s or less.
Blink Reflex - The blink reflex is the involuntary closure of the eyes as the result of stimulation by an external event such as an irritation of the cornea or conjunctiva, a bright flash, the rapid approach of an object, an auditory stimulus, or with facial movements. The ocular aversion response for a bright flash of light is assumed to limit the exposure of a specific retinal area to 0.25 s or less.
Coherent Radiation - Radiation whose waves are in-phase. Laser radiation is coherent and therefore very intense.
Continuous Wave (CW) - A term describing a laser that produces a continuous laser beam while it is operating (verses a pulsed laser beam).
Diffuse Reflection - When an incident radiation beam is scattered in many directions, reducing its intensity. A diffusely reflecting surface will have irregularities larger than the wavelength of the incident radiation beam.
Embedded Laser – An enclosed laser that has a higher classification than the laser system in which it is incorporated, where the system’s lower classification is appropriate due to the engineering features limiting accessible emission.
Incoherent Radiation - Radiation whose waves are not in-phase.
Intrabeam Viewing - The viewing condition whereby the eye is exposed to all or part of a laser beam.
Irradiance - The power being delivered over the area of the laser beam. Also called power density, irradiance applies to CW lasers and is expressed in W/cm2.
Laser – Light Amplification by Stimulated Emission of Radiation. A monochromatic, coherent beam of radiation not normally believed to exist in nature.
Laser Controlled Area (LCA) – An area where the occupancy and activity of those within is subject to control and supervision for the purpose of protection from laser radiation.
Laser User - Any person who uses a laser for any purpose on the UC Berkeley campus or off-campus property.
Laser Safety Manual - A document defining the UC Berkeley Laser Safety Program available on the EH&S website.
Laser Use Authorization (LUA) - The mechanism used by the EH&S to track lasers on campus. The LUA details the safety requirements for each Class 3B and 4 lasers.
Laser Safety Officer (LSO) - A member of the EH&S staff, the laser safety officer (LSO) is responsible for the implementation of the Laser Safety Program.
Maximum Permissible Exposure (MPE) – The level of laser radiation to which an unprotected person may be exposed without 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 may exceed the applicable MPE. Exposure levels beyond the boundary of the NHZ are below the appropriate MPE.
Optical Density (OD) - Also called transmission density, the optical density is the base-ten logarithm of the reciprocal of the transmittance (an OD of 2 = 1% transmittance).
Peak Power - The highest instantaneous power level in a pulse. The peak power is a function of the pulse duration. The shorter the pulse, the greater the peak power.
Radiant Exposure - The energy being delivered over the area of the laser beam. Also called energy density, radiant exposure applies to pulsed lasers and is expressed in J/cm2.
Retinal Hazard Region – Optical radiation with wavelengths between 0.4 and 1.4 μm, where the principal hazard is usually to the retina.
Safety Data Sheet (SDS) - A document, required by law, which is supplied by the manufacturer of a chemical. The SDS details the hazards and protective practices required for protection from those hazards, as well as other information.
Specular Reflection - Results when an incident radiation beam is reflected off a surface whose irregularities are smaller than the radiation wavelength. Specular reflections generally retain most of the power present in the incident beam. Exposure to specular reflections of laser beams is similar to intrabeam exposure.
Standard Operating Procedure (SOP) – Formal written description of the safety and administrative procedures to be followed in performing a specific task. For lasers, SOPs are required for all active Class 3B and 4 lasers. These procedures must include all safety precautions (beam blocks, eyewear, hands-on training, etc.) to be followed.
Ultraviolet (UV) Radiation - Invisible radiation with a wavelength between 10 nm and 400 nm. The near-ultraviolet (UV-A) is the 315 to 400 nm band, the mid ultraviolet (UV-B) is the 280 to 315 nm band, the far ultraviolet (UV-C) is the 100 nm to 280 nm band, and the extreme ultraviolet is the 10 to 100 nm band. Note: Wavelengths below 200 nm are absorbed in the atmosphere and are known as the vacuum ultraviolet.
Visible Light - Radiation that can be detected by the human eye. These wavelengths are between 400 and 780 nm.