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ANSI Z136.1 for Safe Use of Lasers
Reference Document – Section 2 Definitions
March 16, 2009
Compiled by Nikolay Stoev, EWG Chair
Summary
The purpose of this document is to provide a reference for SSCs and TSCs to use when revising
standards that were not updated since the 2007 publication of Z136.1. It shows definitions that were
removed, revised or added in edition 2007 compared with edition 2000. It may also be used for
reference to certain definitions that were deemed unnecessary in Z136.1 and were removed from it, yet
may still be appropriate for inclusion in other standards of the Z136 series.
Definitions should normally be the same throughout all Z136 series of standards unless deviations are
justified, for example in order to make them easier to understand by non-physicists (such as it was done
in Z136.5). Where deliberate definition deviations are introduced, it is advisable to include a note in the
text of the “Definitions” section in the respective standard with a brief explanation why a deviation from
a definition in Z136.1 was necessary.
New and modified definitions are shown in blue.
Where the modification is limited to a word or a phrase, the respective text is highlighted.
Comments from SCCs and TSCs are welcome.
ANSI Z136.1, Edition 2000
ANSI Z136.1, Edition 2007
absorption. Transformation of radiant energy to a different absorption. Transformation of radiant energy to a different
form of energy by interaction with matter.
form of energy by interaction with matter.
accessible emission limit (AEL).
The maximum accessible emission limit (AEL). The maximum accessible
accessible emission level permitted within a particular emission level permitted within a particular laser hazard
class.
class.
accessible optical radiation. Optical radiation to which accessible optical radiation. Optical radiation to which the
the human eye or skin may be exposed for the condition human eye or skin may be exposed for the condition
(operation, maintenance, or service) specified.
(operation, maintenance, or service) specified.
alpha max (max). The angular limit beyond which
extended source MPEs for a given exposure duration are
expressed as a constant radiance or integrated radiance.
This value is defined as 100 mrad.
alpha max. The angular subtense of an extended source
beyond which additional subtense does not contribute to the
hazard and need not be considered. This value is 100 mrad
for retinal thermal effects and 110 mrad for the retinal
photochemical effects. Symbol: αmax
alpha min (min). See limiting angular subtense.
alpha min. The angular subtense of a source below which
the source can be effectively considered as a point source.
The value of alpha min is1.5 mrad. Symbol: αmin
aperture. An opening or window through which radiation aperture. An opening, window, or lens through which
passes.
optical radiation can pass.
aphakic. Term describing an eye in which the crystalline removed
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ANSI Z136.1 for Safe Use of Lasers
Reference Document – Section 2 Definitions
ANSI Z136.1, Edition 2000
ANSI Z136.1, Edition 2007
apparent visual angle. The angular subtense of the source
as calculated from source size and distance from the eye. It
is not the beam divergence of the source (see Section 8.1
and Figure B4 for criteria).
apparent visual angle. The angular subtense (α) of the
source as calculated from source size and distance from the
eye. It is not the beam divergence of the source (see Section
8.1 and Figure B4 for criteria).
lens is absent.
attenuation. The decrease in the radiant flux as it passes attenuation. The decrease in the radiant flux as it passes
through an absorbing or scattering medium.
through an absorbing or scattering medium.
authorized personnel.
Individuals approved by authorized
personnel.
Individuals
approved
by
management to install, operate, or service laser management to operate, maintain, service, or install laser
equipment.
equipment.
average power. The total energy in an exposure or average power. The total energy in an exposure or
emission divided by the duration of the exposure or emission divided by the duration of the exposure or
emission.
emission.
aversion response. Closure of the eyelid, or movement of
the head to avoid an exposure to a noxious stimulant or
bright light. In this standard, the aversion response to an
exposure from a bright laser source is assumed to occur
within 0.25 s, including the blink reflex time.
aversion response. Closure of the eyelid, eye movement,
pupillary constriction, or movement of the head to avoid an
exposure to a noxious or bright light stimulant. In this
standard, 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.
beam. A collection of rays characterized by direction, beam. A collection of light/photonic rays characterized by
diameter (or dimensions), and divergence (or direction, diameter (or dimensions), and divergence (or
convergence).
convergence).
beam diameter. The distance between diametrically
opposed points in that cross-section of a beam where the
power per unit area is 1/e (0.368) times that of the peak
power per unit area.
beam diameter. The distance between diametrically
opposed points in that cross-section of a beam where the
power per unit area is 1/e (0.368) times that of the peak
power per unit area.
beam divergence (). See divergence.
removed (see divergence)
blink reflex. See aversion response.
blink reflex. The blink reflex is the involuntary closure of
the eyes as a 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. In this standard the ocular aversion
response for a bright flash of light is assumed to limit the
exposure of a specific retinal area to 0.25s or less.
CA. Correction factor which increases the MPE values in
the near infrared (IR-A) spectral band (700-1400 nm) based
upon reduced absorption properties of melanin pigment
granules found in the skin and in the retinal pigment
epithelium.
CA. Correction factor which increases the MPE in the near
infrared (IR-A) spectral band (0.7-1.4 μm) based upon
reduced absorption properties of melanin pigment granules
found in the skin and in the retinal pigment epithelium.
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Reference Document – Section 2 Definitions
ANSI Z136.1, Edition 2000
ANSI Z136.1, Edition 2007
CB. Correction factor which increases the MPE values in CB. Correction factor which increases the MPE in the red
the red end of the visible spectrum (450-600 nm), because end of the visible spectrum (0.45-0.60 μm), because of
of greatly reduced photochemical hazards.
greatly reduced photochemical hazards.
CC. Correction factor which increases the MPE values for CC. Correction factor which increases the MPE for ocular
ocular exposure because of pre-retinal absorption of radiant exposure because of pre-retinal absorption of radiant energy
energy in the spectral region between 1150 and 1400 nm.
in the spectral region between 1.15 and 1.40 μm.
CE. Correction factor used for calculating the extended- CE. Correction factor used for calculating the extended
source MPE for the eye from the small-source MPE, when source MPE for the eye from the point source MPE, when
the laser source subtends a visual angle exceeding min.
the laser source subtends a visual angle exceeding min.
CP. Correction factor which reduces the MPE for repetitive- CP. Correction factor which reduces the MPE for repetitivepulse exposure of the eye.
pulse exposure of the eye.
calorimeter. A device for measuring the total amount of removed
energy absorbed from a source of electromagnetic
radiation.
carcinogen. An agent potentially capable of causing carcinogen. An agent potentially capable of causing cancer.
cancer.
coagulation. The process of congealing by an increase in coagulation. The process of congealing by an increase in
viscosity characterized by a condensation of material from viscosity characterized by a condensation of material from a
a liquid to a gelatinous or solid state.
liquid to a gelatinous or solid state.
coherent. A light beam is said to be coherent when the coherent. A beam of light characterized by a fixed phase
electric vector at any point in it is related to that at any other relationship (spatial coherence) or single wavelength, i.e.,
point by a definite, continuous function.
monochromatic (temporal coherence).
collateral radiation. Any electromagnetic radiation, except collateral radiation. Any electromagnetic radiation, except
laser radiation, emitted by a laser or laser system which is laser radiation, emitted by a laser or laser system which is
physically necessary for its operation.
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, microscopes, or loupes.
collecting optics. Lenses or optical instruments having
magnification and thereby producing an increase in energy
or power density. Such devices may include telescopes,
binoculars, microscopes, or loupes.
collimated beam. Effectively, a “parallel” beam of light collimated beam. Effectively, a “parallel” beam of light
with very low divergence or convergence.
with very low divergence or convergence.
Condition 1. Pertains to optically aided viewing of
collimated beams through telescopes or binoculars.
Condition 2. Pertains to optically aided viewing of sources
with highly divergent beams through magnifiers or eye
loupes or unaided viewing with or without strong
accommodation (Condition 2 has slightly different
measurement conditions in IEC 60825-1).
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Reference Document – Section 2 Definitions
ANSI Z136.1, Edition 2000
ANSI Z136.1, Edition 2007
conjunctival discharge (of the eye). Increased secretion removed
of mucus from the surface of the eyeball.
continuous wave (CW). The output of a laser which is continuous wave (CW). In this standard, a laser operating
operated in a continuous rather than a pulsed mode. In this with a continuous output for a period > 0.25 s is regarded as
standard, a laser operating with a continuous output for a a CW laser.
period > 0.25 s is regarded as a CW laser.
controlled area. An area where the occupancy and controlled area (laser). An area where the occupancy and
activity of those within is subject to control and activity of those within is subject to control and supervision
supervision for the purpose of protection from radiation for the purpose of protection from laser radiation hazards.
hazards.
cornea. The transparent outer coat of the human eye which cornea. The transparent outer layer of the human eye which
covers the iris and the crystalline lens. The cornea is the covers the iris and the crystalline lens. The cornea is the
main refracting element of the eye.
main refracting element of the eye.
critical frequency. The pulse repetition frequency above
which the laser output is considered continuous wave
(CW). For a 10 s exposure to a small source, the critical
frequency is 55 kHz for wavelengths between 0.4 and
1.05 m, and 20 kHz for wavelengths between 1.05 and
1.4 m.
critical frequency. The pulse repetition frequency above
which the laser output is considered continuous wave (CW).
For example, for a short unintentional exposure (0.25 s to 10
s) to nanosecond (or longer) pulses, the critical frequency is
55 kHz for wavelengths between 0.40 and 1.05 μm, and 20
kHz for wavelengths between 1.05 and 1.40 μm.
cryogenics. The branch of physical science dealing with removed
very low temperatures.
denaturation. Functional modification of the properties of removed
protein by structural alteration via heat or photochemical
processes.
depigmentation. The removal of the pigment of melanin removed
granules from human tissues.
dermatology. A branch of medical science that deals with removed
the skin, its structure, functions, and diseases.
diffuse reflection. Change of the spatial distribution of a diffuse reflection. Change of the spatial distribution of a
beam of radiation when it is reflected in many directions by beam of radiation when it is reflected in many directions by
a surface or by a medium.
a surface or by a medium.
diopter. A measure of the power of a lens, defined as 1/fo, removed
where fo is the focal length of the lens in meters.
divergence (). For the purposes of this standard,
divergence is taken as the plane angle projection of the
cone that includes 1 - 1/e (i.e. 63.2%) of the total radiant
energy or power. The value of the divergence is expressed
in radians or milliradians.
divergence. In this standard, the divergence is the increase
in the diameter of the laser beam with distance from the exit
aperture, based on the full angle at the point where the
irradiance (or radiant exposure for pulsed lasers) is 1/e times
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Reference Document – Section 2 Definitions
ANSI Z136.1, Edition 2000
NOTE: Many lasers have astigmatic divergence, i.e., have different
divergences in two axes. In such cases, the divergences may be
considered separately or averaged.
ANSI Z136.1, Edition 2007
the maximum value. Symbol: φ
effective energy (Qeff). Energy, in joules, through the effective energy. Energy, in joules, through the applicable
applicable measurement aperture.
measurement aperture. Symbol: Qeff
effective power (eff). Power, in watts, through the effective power. Power, in watts, through the applicable
applicable measurement aperture.
measurement aperture. Symbol: Φeff
electromagnetic radiation. The flow of energy consisting
of orthogonally vibrating electric and magnetic fields lying
transverse to the direction of propagation.
X-ray,
ultraviolet, visible, infrared, and radio waves occupy
various portions of the electromagnetic spectrum and differ
only in frequency, wavelength, and photon energy.
electromagnetic radiation. The flow of energy consisting
of orthogonally vibrating electric and magnetic fields lying
transverse to the direction of propagation. Gamma rays, Xray, ultraviolet, visible, infrared, and radio waves occupy
various portions of the electromagnetic spectrum and differ
only in frequency, wavelength, and photon energy.
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 appropriate due to the engineering
features limiting accessible emission.
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.
enclosed laser. A laser that is contained within a protective
housing of itself or of the laser or laser system in which it is
incorporated. Opening or removing of the protective
housing provides additional access to laser radiation above
the applicable MPE than possible with the protective
housing in place (an embedded laser is an example of one
type of enclosed laser).
enclosed laser. A laser that is contained within a protective
housing of itself or of the laser or laser system in which it is
incorporated. Opening or removing of the protective
housing provides additional access to laser radiation above
the applicable MPE than possible with the protective
housing in place (an embedded laser is an example of one
type of enclosed laser).
endoscope. An instrument utilized for the examination of removed
the interior of a canal or hollow organ.
energy. The capacity for doing work. Energy content is energy. The capacity for doing work. Energy content is
commonly used to characterize the output from pulsed commonly used to characterize the output from pulsed
lasers, and is generally expressed in joules (J).
lasers, and is generally expressed in joules (J).
epidemiology. A branch of medical science that deals with removed
the incidence, distribution, and control of disease in a
population.
epithelium (of the cornea). The layer of cells forming the epithelium (of the cornea). The layer of cells forming the
outer surface of the cornea.
outer surface of the cornea.
erythema. Redness of the skin due to congestion of the erythema. For the purposes of the standard, redness of the
capillaries.
skin due to exposure from laser radiation.
extended source. A source of optical radiation with an extended source. A source of optical radiation with an
angular subtense at the cornea larger than min. See small angular subtense at the cornea larger than αmin. See point
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Reference Document – Section 2 Definitions
ANSI Z136.1, Edition 2000
source.
ANSI Z136.1, Edition 2007
source.
eye-safe laser. A Class 1 laser product. Because of the
frequent misuse of the term “eye-safe wavelength” to mean
“retina-safe,” (e.g., at 1.5-1.6 μm) and eye-safe laser to
refer to a laser emitting at wavelengths outside the retinalhazard region, the term “eye-safe” can be a misnomer.
Hence, the use of eye-safe laser is discouraged.
fail-safe interlock. An interlock where the failure of a fail-safe interlock. An interlock where the failure of a
single mechanical or electrical component of the interlock single mechanical or electrical component of the interlock
will cause the system to go into, or remain in, a safe mode. will cause the system to go into, or remain in, a safe mode.
field of view. The full solid angle from which a detector’s
active area receives radiation.
focal length. The distance, measured in centimeters,
from the secondary nodal point of a lens to the secondary
focal point. For a thin lens imaging a distant source, the
focal length is the distance between the lens and the focal
point.
focal length. The distance from the secondary nodal point
of a lens to the secondary focal point. For a thin lens
imaging a distant source, the focal length is the distance
between the lens and the focal point.
focal point. The point toward which radiation converges focal point. The point toward which radiation converges or
or from which radiation diverges or appears to diverge.
from which radiation diverges or appears to diverge.
fundus. See ocular fundus.
removed
funduscopic. Examination of the fundus (rear) of the eye.
removed
half-power point. The value on either the leading or half-power point. The time on either the leading or trailing
trailing edge of a laser pulse at which the power is one-half edge of a laser pulse at which the power is one-half of its
of its maximum value.
maximum value.
hertz (Hz). The unit which expresses the frequency of a hertz (Hz). The unit which expresses the frequency of a
periodic oscillation in cycles per second.
periodic oscillation in cycles per second.
infrared. The region of the electromagnetic spectrum
between the long-wavelength extreme of the visible
spectrum (about 0.7 m) and the shortest microwaves
(about 1 mm).
infrared. In this standard, the region of the electromagnetic
spectrum between the long wavelength extreme of the
visible spectrum (about 0.7 μm) and the shortest
microwaves (about 1 mm).
infrared radiation.
Electromagnetic radiation with infrared radiation. Electromagnetic radiation with
wavelengths which lie within the range 0.7 m to 1 mm.
wavelengths which lie within the range 0.7 μm to 1 mm.
installation.
Placement and connection of laser installation. Placement and connection of laser equipment
equipment at the appropriate site to enable intended at the appropriate site to enable intended operation.
operation.
integrated radiance. The integral of the radiance over integrated radiance. The integral of the radiance over the
the exposure duration, expressed in joules-per-square- exposure duration, expressed in joules-per-centimeter-
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Reference Document – Section 2 Definitions
ANSI Z136.1, Edition 2000
centimeter per-steradian (Jcm-2sr-1).
ANSI Z136.1, Edition 2007
squared per-steradian (J⋅cm-2⋅sr-1).
intrabeam viewing. The viewing condition whereby the intrabeam viewing. The viewing condition whereby the eye
eye is exposed to all or part of a laser beam (See small- is exposed to all or part of a laser beam.
source viewing).
ionizing radiation. Electromagnetic radiation having a removed
sufficiently large photon energy to directly ionize atomic or
molecular systems with a single quantum event.
iris. The circular pigmented membrane which lies behind iris. The circular pigmented structure which lies behind the
the cornea of the human eye. The iris is perforated by the cornea of the human eye. The iris is perforated by the pupil.
pupil.
irradiance. Radiant power incident per unit area irradiance. Radiant power incident per unit area upon a
upon a surface, expressed in watts-per-square-centimeter surface, expressed in watts-percentimeter-squared (W⋅cm(Wcm-2). Synonym: power density.
2). Symbol: E
Jaeger's test. Samples of type of various sizes printed on a removed
card for testing close visual acuity. An analogue of the
Snellen chart for distant visual acuity.
joule. A unit of energy. 1 joule = 1 watt • second.
joule. A unit of energy. 1 joule = 1 N⋅m; 1 joule = 1 watt •
second.
Lambertian surface. An ideal surface whose emitted or Lambertian surface. An ideal (diffuse) surface whose
emitted or reflected radiance is independent of the viewing
reflected radiance is independent of the viewing angle.
angle.
laser. A device that produces radiant energy predominantly by stimulated emission. Laser radiation may
be highly coherent temporally, or spatially, or both. An
acronym for Light Amplification by Stimulated Emission
of Radiation.
laser. A device that produces radiant energy predominantly
by stimulated emission. Laser radiation may be highly
coherent temporally, or spatially, or both. An acronym for
Light Amplification by Stimulated Emission of Radiation.
laser barrier. A device used to block or attenuate
incident direct or diffuse laser radiation. Laser barriers
are frequently used during times of service to the laser
system when it is desirable to establish a boundary for a
temporary (or permanent) laser controlled area (See
Section 4.6.4).
laser barrier. A device used to block or attenuate incident
direct or diffuse laser radiation. Laser barriers are frequently
used during times of service to the laser system when it is
desirable to establish a boundary for a controlled laser area.
laser classification. An indication of the beam hazard level
of a laser or laser system during normal operation or the
determination thereof. The hazard level of a laser or laser
system is represented by a number or a numbered capital
letter. The laser classifications are Class 1, Class 1M, Class
2, Class 2M, Class 3R, Class 3B and Class 4. In general, the
potential beam hazard level increases in the same order.
laser diode. A laser employing a forward-biased laser diode. A laser employing a forward-biased
semiconductor junction as the active medium. semiconductor junction as the active medium.
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Reference Document – Section 2 Definitions
ANSI Z136.1, Edition 2000
ANSI Z136.1, Edition 2007
Synonyms: injection laser; semiconductor laser.
laser personnel. Persons who routinely work around
hazardous laser beams. This standard requires such persons
to be protected by engineering controls, administrative
procedures, or both.
laser pointer. A Class II or Class IIIa laser product that
is usually hand held that emits a low-divergence visible
beam of less than 5 milliwatts and is intended for
designating specific objects or images during discussions,
lectures or presentations as well as for the aiming of
firearms or other visual targeting practice.
laser pointer. A laser product that is usually hand held that
emits a low-divergence visible beam and is intended for
designating specific objects or images during discussions,
lectures or presentations as well as for the aiming of
firearms or other visual targeting practice. These products
are normally Class 1, Class 2 or Class 3R.
laser safety officer (LSO). One who has authority to laser safety officer (LSO). One who has authority and
monitor and enforce the control of laser hazards and effect responsibility to monitor and enforce the control of laser
the knowledgeable evaluation and control of laser hazards. hazards and effect the knowledgeable evaluation and control
of laser hazards.
laser system. An assembly of electrical, mechanical, and
optical components which includes a laser.
lesion. An abnormal change in the structure of an organ or
part due to injury or disease.
laser system. An assembly of electrical, mechanical, and
optical components which includes a laser.
lesion. An abnormal change in the structure of an organ or
part due to injury or disease.
limiting angular subtense (min). The apparent visual limiting angular subtense. See alpha min.
angle which divides small-source viewing from extendedsource viewing (see Section 8.1 for criteria). min is
defined as 1.5 mrad.
limiting aperture (Df ). The maximum diameter of a limiting aperture diameter. The diameter of a circle over
circle over which radiance and radiant exposure are which irradiance or radiant exposure is averaged for
averaged for purposes of hazard evaluation and purposes of hazard evaluation and classification. Symbol: Df
classification.
limiting cone angle (). Angle of acceptance for
measurement of photochemical hazard for extended
sources with radiance and integrated radiance (see
Section 9.2.1.1, Table 5b and Figure 3).
limiting cone angle. The cone angle through which radiance
or integrated radiance is averaged when photochemical
effects are considered in hazard evaluation and
classification. Symbol: γ
limiting exposure duration (Tmax). An exposure duration limiting exposure duration. An exposure duration which is
which is specifically limited by the design or intended specifically limited by the design or intended use(s).
use(s) (see Section 8 for examples).
Symbol: Tmax
macula. The small uniquely pigmented specialized area of
the retina of the eye, which, in normal individuals, is
predominantly employed for acute central vision (i.e. area
of best visual acuity).
macula. The small uniquely pigmented specialized area of
the retina of the eye, which, in normal individuals, is
predominantly employed for acute central vision (i.e., area
of best visual acuity).
magnified viewing. Viewing a small object through an
optical system that increases the apparent object size. This
type of optical system can make a diverging laser beam
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ANSI Z136.1, Edition 2000
ANSI Z136.1, Edition 2007
more hazardous (e.g., using a magnifying optic to view an
optical fiber with a laser beam emitted).
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. It does not include operation
or service as defined in this section.
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. The criteria for MPE for the eye and skin are detailed
in Section 8.
meter. A unit of length in the international system of
units; currently defined as the length of a path traversed
in vacuum by light during a period of 1/299792458
seconds. Typically, the meter is subdivided into the
following units:
centimeter (cm) = 10-2 m
millimeter (mm) = 10-3 m
micrometer (m) = 10-6 m
nanometer (nm) = 10-9 m
maintenance. Performance of those adjustments or
procedures (specified in the user information provided by
the manufacturer and considered preventative, to maintain
optimal performance of the laser system), which are to be
carried out by the user to ensure the intended performance of
the product. It does not include operation or service as
defined in this section.
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.
measurement aperture. The aperture used for classification
of a laser to determine the effective power or energy that is
compared with the AEL for each laser hazard class.
meter. A unit of length in the international system of units;
currently defined as the length of a path traversed in vacuum
by light during a period of 1/299792458 seconds. Typically,
the meter is subdivided into the following units:
centimeter (cm) = 10-2 m
millimeter (mm) = 10-3 m
micrometer (μm) = 10-6 m
nanometer (nm) = 10-9 m
minimum viewing distance. The minimum distance at
minimum viewing distance. The minimum distance at which the eye can produce a focused image of a diffuse
which the eye can produce a focused image of a diffuse source, usually assumed to be 10 cm.
source, usually assumed to be 10 cm.
monochromatic light. Having or consisting of one color or
wavelength.
nominal hazard zone (NHZ). The space within which the
nominal hazard zone (NHZ). The space within which level of the direct, reflected, or scattered radiation may
the level of the direct, reflected, or scattered radiation exceed the applicable MPE. Exposure levels beyond the
during normal operation exceeds the applicable MPE. boundary of the NHZ are below the appropriate MPE.
Exposure levels beyond the boundary of the NHZ are
below the appropriate MPE level.
nominal ocular hazard distance (NOHD). The distance
nominal ocular hazard distance (NOHD). The distance along the axis of the unobstructed beam from a laser, fiber
along the axis of the unobstructed beam from a laser, end, or connector to the human eye beyond which the
fiber end, or connector to the human eye beyond which irradiance or radiant exposure is not expected to exceed the
the irradiance or radiant exposure, during installation or applicable MPE.
service, is not expected to exceed the appropriate MPE.
non-beam hazard. A class of hazards that result from
non-beam hazard. A class of hazards that result from factors other than direct human exposure to a laser beam.
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factors other than direct human exposure to a laser beam.
normative appendix. Conforming to or based on norms of
an authoritative standard; a principle of right action binding
upon the members of a group and serving to guide, control,
or regulate proper and acceptable behavior.
ocular fundus. The interior posterior surface of the eye (the
ocular fundus. The interior posterior surface of the eye retina), as seen upon ophthalmoscopic examination.
(the retina), as seen upon ophthalmoscopic examination.
operation. The performance of the laser or laser system
operation. The performance of the laser or laser system over the full range of its intended functions (normal
over the full range of its intended functions (normal operation). It does not include maintenance or service as
operation). It does not include maintenance or service as defined in this section.
defined in this section.
ophthalmoscope. An instrument for examining the interior
ophthalmoscope. An instrument for examining the interior of the eye.
of the eye.
optically aided viewing. Viewing with a telescopic
optically aided viewing. Viewing the laser source with (binocular) or magnifying optic. Under certain
an optical device such as an eye loupe, hand magnifier, circumstances, viewing with an optical aid can increase the
microscope, binoculars, telescope, etc. Optically aided hazard from a laser beam (see telescopic viewing or
viewing does not include viewing with corrective magnified viewing).
eyewear or with indirect image converters.
optical density. The logarithm to the base ten of the
optical density (D. Logarithm to the base ten of the reciprocal of the transmittance at a particular wavelength:
reciprocal of the transmittance. That is,
Dλ = log10 (1/τλ)
where τλ is the transmittance at the wavelength of interest.
D = - log10 
Symbol: D(λ), Dλ or OD
where   is the transmittance.
NOTE: The higher the optical density, the lower the transmittance.
Ten times the optical density is equal to the transmission loss
expressed in decibels, e.g., an optical density of 0.3 corresponds to a
transmission loss of 3 dB, i.e., 50 percent.
photochemical effect. A biological effect produced by a
chemical action brought about by the absorption of photons
by molecules that directly alter the molecule.
photophobia. An unusual intolerance of light. Also, an removed
aversion to light usually caused by physical discomfort
upon exposure to light.
photosensitizers. Substances which increase the sensitivity
photosensitizers.
Substances which increase the of a material to exposure by optical radiation.
sensitivity of a material to irradiation by electromagnetic
energy.
pigment epithelium (of the retina). The layer of cells
pigment epithelium (of the retina). The layer of cells which contain brown or black pigment granules next to and
which contain brown or black pigment granules next to and behind the rods and cones.
behind the rods and cones.
plasma radiation. Black-body radiation generated by
plasma radiation. Black-body radiation generated by luminescence of matter in a laser generated plume.
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luminescence of matter in a laser-generated plume.
point source. No longer used. See small source.
point source. For purposes of this standard, a source with
an angular subtense at the cornea equal to or less than alphamin (αmin), i.e., ≤ 1.5 mrad.
point source viewing. The viewing condition whereby the
angular subtense of the source, α, is equal to or less than the
limiting angular subtense, αmin.
power. The rate at which energy is emitted, transferred, or
power. The rate at which energy is emitted, transferred, or received. Unit: watts (W) (joules per second).
received. Unit: watts (joules per second).
protective housing. An enclosure that surrounds the laser or
protective housing. An enclosure surrounding the laser or laser system and prevents access to laser radiation above the
laser system that prevents access to laser radiation above applicable MPE. The aperture through which the useful
the applicable MPE level. The aperture through which the beam is emitted is not part of the protective housing. The
useful beam is emitted is not part of the protective housing. protective housing limits access to other associated radiant
The protective housing may enclose associated optics and a energy emissions and to electrical hazards associated with
workstation, and limits access to other associated radiant components and terminals, and may enclose associated
energy emissions and to electrical hazards associated with optics and a workstation.
components and terminals.
pulse duration. The duration of a laser pulse, usually
pulse duration. The duration of a laser pulse, usually measured as the time interval between the half-power points
measured as the time interval between the half-power on the leading and trailing edges of the pulse. Typical units:
points on the leading and trailing edges of the pulse.
microsecond (μs) = 10-6 s
nanosecond (ns) = 10-9 s
picosecond (ps) = 10-12 s
femtosecond (fs) = 10-15 s
Symbol: t
pulse-repetition frequency (PRF). The number of pulses
pulse-repetition frequency (PRF). The number of occurring per second, expressed in hertz. Symbol: F.
pulses occurring per second, expressed in hertz.
pulsed laser. A laser which delivers its energy in the form
pulsed laser. A laser which delivers its energy in the form of a single pulse or a train of pulses. In this standard, the
of a single pulse or a train of pulses. In this standard, the duration of a pulse is less than 0.25 s.
duration of a pulse < 0.25 s.
pupil. The variable aperture in the iris through which light
pupil. The variable aperture in the iris through which light travels to the interior of the eye.
travels to the interior of the eye.
Q-switch. A device for producing very short (~10-250 ns),
Q-switch. A device for producing very short (~10-250 ns), intense laser pulses by enhancing the storage and dumping
intense laser pulses by enhancing the storage and dumping of electronic energy in and out of the lasing medium,
of electronic energy in and out of the lasing medium, respectively.
respectively.
Q-switched laser. A laser that emits short (~10-250 ns),
Q-switched laser. A laser that emits short (~10-250 ns), high-power pulses by means of a Q-switch.
high-power pulses by means of a Q-switch.
radian (rad). A unit of angular measure equal to the angle
radian (rad). A unit of angular measure equal to the angle subtended at the center of a circle by an arc whose length is
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subtended at the center of a circle by an arc whose length is equal to the radius of the circle. 1 radian ~ 57.3 degrees; 2π
equal to the radius of the circle. 1 radian ~ 57.3 degrees; 2 radians = 360 degrees.
radians = 360 degrees.
radiance. Radiant flux or power output per unit solid angle
radiance. Radiant flux or power output per unit solid angle per unit area expressed in wattsper-centimeter squared perper unit area expressed in watts-per-centimeter squared-per- steradian (W⋅cm-2⋅ sr-1). Symbol: L
steradian (W  cm-2  sr-1).
radiant energy. Energy emitted, transferred, or received in
radiant energy. Energy emitted, transferred, or received in the form of radiation. Unit: joules (J). Symbol: Q
the form of radiation. Unit: joules (J).
radiant exposure. Surface density of the radiant energy
radiant exposure. Surface density of the radiant energy received, expressed in units of joulesper-centimeter squared
received, expressed in units of joules-per-centimeter (J⋅cm-2). Symbol: H
squared (Jcm-2).
radiant flux. Power emitted, transferred, or received in the
radiant flux. Power emitted, transferred, or received in the form of radiation. Unit: watts (W). Also called radiant
form of radiation. Unit: watts (W). Also called radiant power. Symbol: Φ
power.
removed
radiant intensity. Quotient of the radiant flux leaving a
source and propagated into an element of solid angle
containing the direction, by the element of solid angle.
Radiant intensity is expressed in units of watts per
steradian (Wsr-1).
radiant power. Power emitted, transferred, or received in
radiant power. Power emitted, transferred, or received the form of radiation, expressed in watts (W). Synonym:
in the form of radiation, expressed in watts (W). radiant flux.
Synonym: radiant flux.
radiometry. For the purposes of this standard, the
radiometry. A branch of science that deals with the measurement of infrared, visible, and ultraviolet radiation.
measurement of radiation. For the purposes of this
standard, radiometry will be limited to the measurement of
infrared, visible, and ultraviolet radiation.
removed
Rayleigh scattering. Scattering of radiation in the course
of its passage through a medium containing particles whose
sizes are small compared with the wavelength of the
radiation.
reflectance. The ratio of total reflected radiant power to
reflectance. The ratio of total reflected radiant power to total incident power. Also called “reflectivity.”
total incident power. Also called reflectivity.
reflection. Deviation of radiation following incidence on a
reflection. Deviation of radiation following incidence on a surface.
surface.
refraction. The bending of a beam of light in transmission
refraction.
The bending of a beam of light in through an interface between two dissimilar media or in a
transmission through an interface between two dissimilar medium whose refractive index is a continuous function of
media or in a medium whose refractive index is a position (graded index medium).
continuous function of position (graded index medium).
refractive index (of a medium). Denoted by n, the ratio of
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refractive index (of a medium). Denoted by n, the ratio the velocity of light in a vacuum to the phase velocity in the
of the velocity of light in vacuum to the phase velocity in medium. Synonym: index of refraction.
the medium. Synonym: index of refraction.
repetitive pulse laser. A laser with multiple pulses of
repetitive pulse laser. A laser with multiple pulses of radiant energy occurring in a sequence.
radiant energy occurring in a sequence.
retina. The sensory tissue that receives the incident image
retina. The sensory membrane that receives the incident formed by the cornea and lens of the human eye.
image formed by the cornea and lens of the human eye. The
retina lines the inside of the eye.
retinal hazard region. Optical radiation with wavelengths
retinal hazard region.
Optical radiation with between 0.4 and 1.4 μm, where the principal hazard is
wavelengths between 0.4 and 1.4 m, where the principal usually to the retina.
hazard is usually to the retina.
safety latch. A mechanical device designed to require a
safety latch. A mechanical device designed to slow direct conscious decision to override the latch to gain entry into a
entry to a controlled area.
controlled area.
scanning laser. A laser having a time-varying direction,
scanning laser. A laser having a time-varying direction, origin, or pattern of propagation with respect to a stationary
origin, or pattern of propagation with respect to a stationary frame of reference.
frame of reference.
scintillation. The rapid changes in irradiance levels in a
scintillation. The rapid changes in irradiance levels in a cross-section of a laser beam.
cross-section of a laser beam.
secured enclosure. An enclosure to which casual access is
secured enclosure. An enclosure to which casual access impeded by an appropriate means, e.g., a door secured by a
is impeded by an appropriate means, e.g., a door secured magnetically or electrically operated lock or latch, or by
by a magnetically or electrically operated lock or latch, or fasteners that need a tool to remove.
by fasteners that need a tool to remove.
service. The performance of procedures, typically defined as
service.
The performance of those procedures or repair, to bring the laser or laser system or laser product
adjustments described in the manufacturer's service back to full and normal operational status. It does not
instructions which may affect any aspect of the include operation or maintenance as defined in this section.
performance of the laser or laser system. It does not
include maintenance or operation as defined in this section.
shall. The word shall is to be understood as mandatory.
shall. The word “shall” is to be understood as mandatory.
should. The word should is to be understood as advisory.
should. The word “should” is to be understood as
advisory.
removed, back to “point source”
small source. In this document, a source with an angular
subtense at the cornea equal to or less than alpha-min (
This includes all sources
min), i.e.,  than 1.5 mrad.
formerly referred to as “point sources” and meeting
small-source viewing (formerly called point source or
intrabeam viewing) conditions. (See Section 8.1 for
criteria).
removed, see “point-source viewing”
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small-source viewing. The viewing condition whereby
the angular subtense of the source, min, is equal to or less
than the limiting angular subtense, min (See Section 8.1
for criteria).
NOTE: Small-source viewing was formerly called “intrabeam”
viewing.
solid angle. The three-dimensional angular spread at the
solid angle. The three-dimensional angular spread at the vertex of a cone measured by the area intercepted by the
vertex of a cone measured by the area intercepted by the cone on a unit sphere whose center is the vertex of the cone.
cone on a unit sphere whose center is the vertex of the Solid angle is expressed in steradians (sr).
cone. Solid angle is expressed in steradians (sr).
source. A laser or a laser-illuminated reflecting surface.
source. A laser or a laser-illuminated reflecting surface.
spectator. An individual who wishes to observe or watch a
spectator. An individual who wishes to observe or watch a laser or laser system in operation, and who may lack the
laser or laser system in operation, and who may lack the appropriate laser safety training.
appropriate laser safety training.
specular reflection. A mirror-like reflection.
specular reflection. A mirror-like reflection.
steradian (sr). The unit of measure for a solid angle. There
steradian (sr). The unit of measure for a solid angle. are 4π steradians about any point in space.
There are 4 steradians about any point in space.
standard operating procedure (SOP). Formal written
standard operating procedure (SOP). Formal written description of the safety and administrative procedures to be
description of the safety and administrative procedures to followed in performing a specific task.
be followed in performing a specific task.
removed
stromal haze (of the cornea).
Cloudiness in the
connective tissue or main body of the cornea.
removed
surface exfoliation (of the cornea). A stripping or peeling
off of the surface layer of cells from the cornea.
removed
synergism. A condition in which the combined effect is
greater than the sum of the effects of individual
contributors.
T1. The exposure duration (time) at which MPEs based upon
T1. The exposure duration (time) at which MPEs based thermal injury are replaced by MPEs based upon
upon thermal injury are replaced by MPEs based upon photochemical injury to the retina.
photochemical injury to the retina.
T2. The exposure duration (time) beyond which extended
T2. The exposure duration (time) beyond which extended- source MPEs based upon thermal injury are expressed as a
source MPEs based upon thermal injury are expressed as a constant irradiance.
constant irradiance.
Tmax. The total expected or anticipated exposure duration
Tmax. See limiting exposure duration.
(see Section 3 for classification; see Section 8 for intended
use determination). Tmax may differ depending upon its
use.
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telescopic viewing. Viewing an object from a long distance
with the aid of an optical system that increases the visual
size of the image. The system (e.g., binoculars) generally
collects light through a large aperture thus magnifying
hazards from large-beam, collimated lasers.
thermal effect. An effect brought about by the temperature
elevation of a substance due to laser exposure.
threshold limit (TL). In this standard, the term is
applied to laser protective eyewear filters, protective
windows, and barriers. The TL is an expression of the
“resistance factor” for beam penetration of a laser
protective device. This is generally related by the
Threshold Limit (TL) of the protective device (expressed
in Wcm-2 or Jcm-2). It is the maximum average
irradiance (or radiant exposure) at a given beam diameter
for which a laser protective device (e.g. filter, window,
barrier, etc.) provides adequate beam resistance. Thus,
laser exposures delivered on the protective device at or
below the TL will limit beam penetration to levels at or
below the applicable MPE.
tmin. For a pulsed laser, the maximum duration for which
the MPE is the same as the MPE for a 1 ns exposure. For
thermal biological effects, this corresponds to the “thermal
confinement duration” during which heat flow does not
significantly change the absorbed energy content of the
thermal relaxation volume of the irradiated tissue
(Example: tmin is 18 s in the spectral region 0.4 to 1.05 m
and is 50 s between 1.050 and 1.400 m).
threshold limit (TL). The term is applied to laser protective
eyewear filters, protective windows, and barriers. The TL is
an expression of the “resistance factor” for beam penetration
of a laser protective device. This is generally related by the
Threshold Limit (TL) of the protective device, expressed in
W⋅cm-2 or J⋅cm-2. It is the maximum average irradiance or
radiant exposure at a given beam diameter for which a laser
protective device provides adequate beam resistance. Thus,
laser exposures delivered on the protective device at or
below the TL will limit beam penetration to levels at or
below the applicable MPE.
tmin. For a pulsed laser, the maximum duration for which the
MPE is the same as the MPE for a 1 ns exposure. For
thermal biological effects, this corresponds to the “thermal
confinement duration” during which heat flow does not
significantly change the absorbed energy content of the
thermal relaxation volume of the irradiated tissue.
removed
tonometry. Measurement of the pressure (tension) of the
eyeball.
transmission. Passage of radiation through a medium.
transmission. Passage of radiation through a medium.
transmittance.
incident power.
transmittance. The ratio of transmitted power (energy) to
The ratio of transmitted power to incident power (energy).
ultraviolet radiation. In this standard, electromagnetic
ultraviolet radiation. Electromagnetic radiation with radiation with wavelengths between 0.18 and 0.40 μm
wavelengths shorter than those of visible radiation; for the (shorter than those of visible radiation).
purpose of this standard, 0.18 to 0.4 m.
uncontrolled area. An area where the occupancy and
uncontrolled area. An area where the occupancy and activity of those within is not subject to control and
activity of those within is not subject to control and supervision for the purpose of protection from radiation
supervision for the purpose of protection from radiation hazards.
hazards.
viewing window. A visually transparent part of an enclosure
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viewing window. Visually transparent parts of enclosures that contains a laser process. It may be possible to observe
that contain laser processes. It may be possible to the laser processes through the viewing windows.
observe the laser processes through the viewing windows.
visible radiation (light). The term is used to describe
visible radiation (light). In this standard, the term is used electromagnetic radiation which can be detected by the
to describe electromagnetic radiation which can be detected human eye. In this standard, this term is used to describe
by the human eye. This term is commonly used to describe wavelengths which lie in the range 0.4 to 0.7 μm. Derivative
wavelengths which lie in the range 0.4 to 0.7 m.
standards may legitimately use 0.38 – 0.78 μm for the
visible radiation range.
watt (W). The unit of power or radiant flux. 1 watt = 1
watt (W). The unit of power or radiant flux. 1 watt = 1 joule-per-second.
joule-per-second.
wavelength. The distance in the line of advance of a
wavelength. The distance between two successive points sinusoidal wave from any one point to the next point of
on a periodic wave which have the same phase.
corresponding phase (e.g., the distance from one peak to the
next).
work practices. Procedures used to accomplish a task.
work practices. Procedures used to accomplish a task.
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