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Appendix B

Glossary

Accessible laser radiation. Laser radiation to which the human eye or skin may be exposed for the condition (operation, maintenance or service) specified.

American National Standard for Safe Use of Lasers (ANSI Z136.1-2007.) Document that provides guidance for the safe use of lasers and laser systems by defining control measures for each of four laser classifications. The University of Pennsylvania has adopted this standard as a minimum standard for laser safety.

Attenuation. The decrease in the radiant flux as it passes through an absorbing or scattering medium.

Authorized personnel. Individuals approved by the Principal Investigator to install, operate or service laser equipment.

Average power. The total energy in an exposure or emission divided by the duration of the exposure or emission.

Aversion response. Closure of the eyelid or movement of the head to avoid an exposure to a noxious stimulant or bright light. Aversion response to an exposure from a bright laser source is assumed to occur within .25 s, including the blink reflex time.

Collateral radiation. Any electronic radiation, except laser radiation, emitted by a laser or laser system that is physically necessary for its operation.

Collecting optics. Lenses or optical instruments having magnification and thereby producing an increase in energy or power density. Such devices may include telescopes, binoculars or loupes.

Continuous wave (CW). The output of a laser that is operated in a continuous rather than a pulsed mode. For purposes of safety evaluation, a laser operating with a continuous output for a period > 0.25 s is regarded as a CW laser.

Controlled area. An area where the occupancy and activity of those within is subject to control and supervision for the purpose of protection from laser radiation and related 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. An enclosed laser with an assigned class number higher than the inherent capability of the laser system in which it is incorporated, where the system's lower classification is the result of engineering features which limits the accessible emission.

Failsafe interlock. An interlock where the failure of a single mechanical or electrical component of the interlock will cause the system to go into, or remain in, a safe mode.

Incident personnel. Individuals working in areas where there is a potential for exposure to laser radiation from a Class 3b or Class 4 laser, but do not operate the laser.

Infrared radiation. Electromagnetic radiation with wavelengths that lie within the range 0.7 µm to 1 mm.

Intrabeam viewing. The viewing condition whereby the eye is exposed to all or part of a laser beam.

Laser operator. See Authorized Personnel.

Laser controlled area. See Controlled Area.

Laser Safety Officer (LSO). One who has the authority to monitor and enforce the control of laser hazards and effect the knowledgeable evaluation and control of laser hazards. The LSO for the University of Pennsylvania is on the staff of EHRS.

Laser system. An assembly of electrical, mechanical, and optical components that includes one or more lasers.

Maintenance. Performance of those adjustments or procedures specified in user information provided by the manufacturer with the laser or laser system, which are to be performed by the user to ensure the intended performance of the product.

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. MPE is expressed in terms of either radiant exposure (joules/cm2) or irradiance (watts/cm2). The criteria for MPE are detailed in Section 8 of ANSI Z136.1.

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.)

Operation. The performance of the laser or laser system over the full range of its intended functions (normal operation.)

Optical density. Logarithm to the base ten of the reciprocal of the transmittance. The higher the optical density, the lower the transmittance.

Pulsed laser. A laser that delivers its energy in the form of a single pulse or a train of pulses. The duration of a pulse is regarded to be < 0.25 s.

Q-switch. A device for producing very short (10-250 ns) intense laser pulses by enhancing the storage and dumping of electronic energy in and out of the lasing medium, respectively.

Repetitive pulse laser. A laser with multiple pulses of radiant energy occurring in sequence.

Reversible bleaching. The absorbing filter of laser eyewear may become temporarily saturated from an ultrashort laser pulse, causing the beam to pass through.

Service. The performance of those procedures or adjustments described in the manufacturer's service instructions that may affect any aspect of the performance of the laser or laser system. These are usually performed by qualified technical personnel provided by the manufacturer or other service companies.

Shall. The word “shall” is to be understood as mandatory.

Should. The word “should” is to be understood as advisory.

Specular reflection. A mirror-like reflection.

Ultraviolet radiation. Electromagnetic radiation with wavelengths smaller than those of visible radiation; for the purpose of this manual, 0.18 to 0.4 µm.

Visible radiation (light). Electromagnetic radiation that can be detected by the human eye. This term is commonly used to describe wavelengths that lie in the range 0.4 to 0.7 µm.

Wavelength. The distance between two successive points on a periodic wave which have the same phase.

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