IEC TR 60825-13:2011

IEC/TR 60825-13 ®
Edition 2.0 2011-10
TECHNICAL
REPORT
colour
inside
Safety of laser products –
Part 13: Measurements for classification of laser products

IEC/TR 60825-13:2011(E)
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IEC/TR 60825-13 ®
Edition 2.0 2011-10
TECHNICAL
REPORT
colour
inside
Safety of laser products –
Part 13: Measurements for classification of laser products

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
XB
ICS 31.260 ISBN 978-2-88912-741-2

– 2 – TR 60825-13  IEC:2011(E)
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Applicability . 8
4.1 General . 8
4.2 Initial considerations . 8
5 Instrumentation requirements . 9
6 Classification flow. 10
7 Parameters for calculation of accessible emission limits . 12
7.1 Wavelength (λ) . 12
7.1.1 Wavelength determination . 12
7.1.2 Ocular hazard regions . 14
7.2 Multiple wavelength sources . 14
7.2.1 General . 14
7.2.2 Single hazard region . 15
7.2.3 Two or more hazard regions . 15
7.3 Spectrally broad sources . 15
7.3.1 General . 15
7.3.2 Spectral regions with small variation of the AEL with wavelength . 15
7.3.3 Spectral regions with large variation of the AEL with wavelength
(302,5 nm - 315 nm, 450 nm – 600 nm and 1 150 nm – 1 200 nm) . 16
7.3.4 Spectral regions containing hazard-type boundaries (near 400 nm
and 1 400 nm) . 16
7.3.5 Very broad sources . 16
7.4 Source temporal characteristics . 17
7.4.1 General . 17
7.4.2 Sources with limited “ON” time . 17
7.4.3 Periodic or constant duty factor sources . 17
7.4.4 Sources with amplitude variation . 19
7.4.5 Sources with varying pulse durations or irregular pulses . 20
7.5 Angular subtense (α) . 20
7.5.1 General . 20
7.5.2 Location of the reference point . 22
7.5.3 Methods for determining angular subtense (α) . 23
7.5.4 Multiple sources and simple non-circular beams . 26
7.6 Emission duration . 31
7.6.1 General . 31
7.6.2 Pulse duration . 31
7.6.3 Pulse repetition frequency . 31
7.7 Measurement conditions . 31
7.7.1 General . 31
7.7.2 Measurement conditions for classification . 31
7.7.3 Measurement conditions for hazard evaluation . 33
7.8 Scanning beams . 36
7.8.1 General . 36

TR 60825-13  IEC:2011(E) – 3 –
7.8.2 Stationary angular subtense (α ) . 36
s
7.8.3 Scanned pulse duration (T ) . 37
p
7.8.4 Scanning angular subtense (α ) . 38
scan
7.8.5 Bi-directional scanning . 39
7.8.6 Number of scan lines in aperture (n) . 39
7.8.7 Maximum hazard location . 40
7.8.8 Gaussian beam coupling parameter (η) . 41
7.8.9 Scan angle multiplication factor . 41
Annex A (informative) Examples . 43
Annex B (informative) Useful conversions . 64
Bibliography . 65

Figure 1 – Continuous wave laser classification flow . 11
Figure 2 – Pulsed laser classification flow . 12
Figure 3 – Important wavelengths and wavelength ranges . 13
Figure 4 – Pulse duration definition . 18
Figure 5 – Flat-topped and irregular pulses . 20
Figure 6 – Angular subtense . 21
Figure 7 – Location of beam waist for a Gaussian beam . 23
Figure 8a – Measurement set-up with source imaging . 24
Figure 8b – Measurement set-up for accessible source . 26
Figure 8 – Apparent source measurement set-ups . 26
Figure 9 – Linear array apparent source size . 27
Figure 10 – Measurement geometries . 29
Figure 11 – Effective angular subtense of a simple non-circular source . 30
Figure 12 – Imaging a stationary apparent source located beyond the scanning beam
vertex . 37
Figure 13 – Imaging a scanning apparent source located beyond the scanning beam
vertex . 37
Figure 14 – Scanning mirror with an arbitrary scan angle multiplication factor . 42
Figure A.1 – Multiple raster lines crossing the measurement aperture at distance from
scanning vertex where C = 1 . 49
Table 1 – Reference points . 22
Table 2 – Four source array . 28
Table A.1 – Number of source cases . 62
Table A.2 – Number of source cases . 63

– 4 – TR 60825-13  IEC:2011(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
___________
SAFETY OF LASER PRODUCTS –
Part 13: Measurements for classification of laser products

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
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with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
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5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
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6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
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other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
The main task of IEC technical committees is to prepare International Standards. However, a
technical committee may propose the publication of a technical report when it has collected
data of a different kind from that which is normally published as an International Standard, for
example "state of the art".
IEC 60825-13, which is a technical report, has been prepared by IEC technical committee 76:
Optical radiation safety and laser equipment.
This second edition cancels and replaces the first edition of IEC 60825-13, published in 2006.
It constitutes a technical revision.
The main changes with respect to the previous edition are as follows:
Minor changes and additions have been made in the definitions, classification flow has been
updated, apparent source sections have been clarified, scanning has been updated, and more
examples and useful conversions have been added to the annexes.

TR 60825-13  IEC:2011(E) – 5 –
The text of this technical report is based on the following documents:
Enquiry draft Report on voting
76/424/DTR 76/447/RVC
Full information on the voting for the approval of this technical report can be found in the
report on voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
This technical report is to be used in conjunction with IEC 60825-1:2007.
A list of all parts of the IEC 60825 series, published under the general title Safety of laser
products, can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.

IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
– 6 – TR 60825-13  IEC:2011(E)
SAFETY OF LASER PRODUCTS –
Part 13: Measurements for classification of laser products

1 Scope
This part of IEC 60825 provides manufacturers, test houses, safety personnel, and others
with practical guidance on methods to perform radiometric measurements or analyses to
establish the emission level of laser energy in accordance with IEC 60825-1:2007 (herein
referred to as “the standard”). The measurement procedures described in this technical report
are intended as guidance for classification of laser products in accordance with that standard.
Other procedures are acceptable if they are better or more appropriate.
Information is provided for calculating accessible emission limits (AELs) and maximum
permissible exposures (MPEs), since some parameters used in calculating the limits are
dependent upon other measured quantities.
This document is intended to apply to lasers, including extended sources and laser arrays.
Users of this document should be aware that the procedures described herein for extended
source viewing conditions may yield more conservative results than when using more rigorous
methods.
NOTE Work continues on more complex source evaluations and will be provided as international agreement on
the methods is reached.
2 Normative references
The following referenced document is indispensable for the application of this document. For
dated references, only the edition cited applies. For undated references, the latest edition of
the referenced document (including any amendments) applies.
IEC 60825-1:2007, Safety of laser products – Part 1: Equipment classification and
requirements
3 Terms and definitions
For the purposes of this document, the terms and definitions contained in IEC 60825-1:2007
as well as the following terms and definitions apply.
3.1
angular velocity
speed of a scanning beam in radians per second
3.2
beam profile
irradiance distribution of a beam cross-section
3.3
beam waist
minimum diameter of an axis-symmetric beam
Note 1 to entry: For non-symmetric beams, there may be a beam waist along each major axis, each located at a
different distance from the source.

TR 60825-13  IEC:2011(E) – 7 –
3.4
charge-coupled device
CCD
self-scanning semiconductor imaging device that utilizes metal-oxide semiconductor (MOS)
technology, surface storage, and information transfer
3.5
critical frequency
pulse repetition frequency above which a pulsed laser can be modelled as CW for the
purposes of laser hazard evaluation
3.6
Gaussian beam profile
profile of a laser beam which is operated in the lowest transverse mode, TEM
NOTE 1 to entry: A Gaussian beam profile may also be produced by passing non-TEM laser beams through
beam shaping optical elements.
3.7
measurement aperture
aperture used for classification of a laser to determine the power or energy that is compared
to the AEL for each class
3.8
pulse repetition frequency
PRF
number of pulses occurring per second, expressed in hertz (Hz)
3.9
Q-switch
device for producing very short, high peak power laser pulses by enhancing the storage and
dumping of energy in and out of the lasing medium, respectively
3.10
Q-switched laser
aser that emits short, high-power pulses by means of a Q-switch
3.11
Rayleigh length
Z
r
distance from the beam waist in the direction of propagation for which the beam diameter or
beam widths are equal to 2 times that at the beam waist
NOTE 1 to entry: Rayleigh length is often referred to as ½ the confocal parameter.
3.12
responsivity
R
ratio of the output of a detector to the corresponding input expressed as R = O/I, where O is
the detector’s electrical output and I is the optical power or energy input
3.13
Ultrashort pulse laser
laser that emits pulses shorter than 100 fs and can contain a relatively large spectral content

– 8 – TR 60825-13  IEC:2011(E)
4 Applicability
4.1 General
This report is intended to be used as a reference guide by (but not limited to) manufacturers,
testing laboratories, safety officers, and officials of industrial or governmental authorities. This
report also contains interpretations of the standard pertaining to measurement matters and
provides supplemental explanatory material.
4.2 Initial considerations
Before attempting to make radiometric measurements for the purpose of product classification
or compliance with the other applicable requirements of the standard, there are several
parameters of the laser that must first be determined.
a) Emission wavelength(s)
Lasers may emit radiation at one or more distinct wavelengths.
The emission wavelength, wavelengths, or spectral wavelength distribution can typically
be obtained from the manufacturer of the laser. Depending on the type of laser, the
manufacturer may specify a wavelength range rather than a single value. Otherwise, the
emission wavelength, wavelengths or spectral distribution can be determined by
measurement, which is beyond the scope of this technical report. See 7.1 for assessing
the accessible emission limit (AEL) for multiple wavelengths.
b) Time mode of operation
The time mode of operation refers to the rate at which the energy is emitted. Some lasers
emit continuous wave (CW) radiation; other lasers emit energy as pulses of radiation.
Pulsed lasers may be single pulsed, Q-switched, repetitively pulsed, or mode locked.
Scanned or modulated CW radiation at a fixed location also results in a train of pulses.
In addition, the pulse train may be encoded, but have an average duty factor (emission
time as a fraction of elapsed time, expressed as a decimal fraction or percentage).
c) Reasonably foreseeable single fault conditions
The standard specifies that tests shall be performed under each and every reasonably
foreseeable single fault condition. It is the responsibility of the manufacturer to ensure that
the accessible radiation does not exceed the AEL of the assigned class under all such
conditions.
d) Measurement uncertainties
It is important to consider potential sources of error in measurement of laser radiation.
Clause 5 of this technical report addresses measurement uncertainties.
e) Collateral radiation (see the standard for definition of collateral radiation)
Collateral radiation entering the measurement aperture may affect measured values of
power or energy and pulse duration. Test personnel should ensure that the measurement
setup blocks or accounts for collateral radiation that would otherwise reach the detector.
f) Product configuration
If measurements are being made for the purpose of classification, then all controls and
settings listed in the operation, maintenance and service instructions must be adjusted in
combination to result in the maximum accessible level of radiation. Measurements are also
required with the use of accessories that may increase the radiation hazard (for example,
collimating optics) which are supplied or offered by the manufacturer of the laser product
for use with the product.
NOTE This includes any configuration of the product, which it is possible to attain without using tools or
defeating an interlock including configurations and settings against which the operation and maintenance
instructions contain warnings. For example, when optical elements such as filters, diffusers or lenses in the
optical path of the laser beam can be removed without tools, the product is to be tested in the configuration
which results in the highest hazard level. The instruction by the manufacturer not to remove the optical
elements cannot justify classification as a lower class. Classification is based on the engineering design of the
product and cannot be based on appropriate behaviour of the user.

TR 60825-13  IEC:2011(E) – 9 –
If measurements are being made to determine the requirements for safety interlocks,
labels and information for the user, then the product must be evaluated under the
configurations applicable for each of the defined categories of use (operation,
maintenance, and service) in accordance with the standard.
IEC technical committee 76 (TC 76) recognises the existence of equivalent measurement
procedures, which could yield results that are as valid as the procedures described in this
technical report. This report describes measurement procedures that are adequate to meet
the measurement requirements of the standard when measurements are needed. In many
cases actual radiometric measurements may not be necessary, and compliance with the
requirements of the standard can be determined from an analysis of a well-characterised
source and the design of the actual product.
Measurements of accessible emission levels must be made at points in space to which human
access is possible during operation and maintenance, as applicable. (For example, if
operation may require removal of portions of the protective housing and defeat of safety
interlocks, measurements must be made at points accessible in that product configuration.)
Therefore, under some circumstances it may be necessary to partially disassemble a product
to undertake measurements at the required measurement location, particularly when
considering reasonably foreseeable single fault conditions. Where a final laser product
contains other laser products or systems, it is the final product that is subject to the provisions
of the standard.
Measurements must be made with the measuring instrument detector so positioned and so
oriented with respect to the laser product as to result in the maximum detection of radiation by
the instrument. That is, the detector may have to be moved or the angle changed to obtain a
maximum reading on the meter. Appropriate provision must be made to avoid or to eliminate
the contribution of collateral radiation to the measurement. For example, it may be necessary
to take measurements some distance away from a laser system’s output to avoid corrupting
the data with radiation from flash lamps or pump diodes/diode lasers. As another example, it
may be necessary to filter collateral radiation out with a line filter.
5 Instrumentation requirements
Measurement instruments to be used should comply with the latest edition of IEC 61040.
Which instrument class (between class 1 and class 20 giving the approximate value of the
possible measurement uncertainty) is to be used depends on the measurement accuracy
needed.
Where instruments not fully compliant with IEC 61040 are used, the individual contributions of
different parameters to the total measurement uncertainty have to be evaluated separately.
The main points to be considered are those given in IEC 61040:
• change of responsivity with time;
• non-uniformity of responsivity over the detector surface;
• change of responsivity during irradiation;
• temperature dependence of responsivity;
• dependence of responsivity on the angle of incidence;
• non-linearity;
• wavelength dependence of responsivity;
• polarisation dependence of responsivity;
• errors in averaging of repetitively pulsed radiation over time;
• zero drift;
• calibration uncertainty.
– 10 – TR 60825-13  IEC:2011(E)
Calibrations should be traceable to national standards.
Tests for the determination of measurement uncertainties of the instrument should be done
according to IEC 61040.
For measurement uncertainties of CCD arrays and cameras see ISO 11146-3.
6 Classification flow
Known or measured parameters of the product enable calculation of AELs and measurement
conditions. In addition, fault conditions that increase the hazard must be analysed. Then, a
product emission measurement (or several different measurements) will determine if the
emission is within the AEL of the class under consideration.
Tables 4 to 9 in the standard provide the accessible emission limits. These tables have rows
for the wavelength ranges and columns for the emission durations. Within each row and
column entry, there exist one or more formulas containing parameters that are defined in
Table 10 in the standard.
The classification flow is illustrated in Figures 1 and 2. The initial approach is to use the
default simplified evaluation from 9.3.2 in the standard. It considers the beam to be emitted
from a small (point) source with C = 1, a conservative approach if the apparent source size is
not known. If the product output appears to be generated by an extended source and is in the
400 nm – 1400 nm range, and if the class determined by the simplified evaluation is not
acceptable, then one can alternately determine the class using the more complex evaluation.
This involves using additional parameters, including the angular subtense α as a function of
distance and the measurement acceptance angle γ for the visible photochemical hazard.
p
First determine whether the laser is pulsed or continuous wave. If the pulse duration is
greater than 0,25 s, the laser is considered continuous wave. For a continuous wave laser,
refer to the flowchart in Figure 1, and for a pulsed laser, refer to the flowchart in Figure 2.
Next, the wavelength must be determined.
If the laser is pulsed or scanned, the pulse width (PW) and pulse repetition frequency (PRF)
must also be determined.
Determine the applicable class or classes. For instance, for a low power application not in the
400 nm – 700 nm region, Class 1, Class 1M and Class 3R might be considered. For a visible
wavelength source, Class 1, Class 1M, Class 2, Class 2M and Class 3R might be considered.
Next, the classification time base must be established. This can be determined in terms of
default values (8.3e) in the standard), or determined from the definition of the T parameter
(Table 10 in the standard), or from considering the particular temporal output properties of the
product in question.
This information is needed to locate the row and column entries of Tables 4 to 9 in the
standard containing the formula or formulas of interest, and thus to determine the AELs.
Next, the measurement conditions must be determined (9.3 and Table 11 of the standard).
For a pulsed laser, several conditions given in 8.3f) of the standard must be evaluated to
ensure all fall within the AEL.
Once the AEL has been determined, the output data should be evaluated. The output data
may be provided by the manufacturer or measured directly. If output data are provided by the
manufacturer, it must be confirmed that the measurements were performed in accordance
with Clause 9 of the standard. If the accessible emission is less than the AEL, the laser may

TR 60825-13  IEC:2011(E) – 11 –
be assigned to that class. For a pulsed laser, the AEL of the class applies for all emission
durations within the time base.
If the accessible emission is not less than the AEL, a higher class AEL should be chosen and
assessed. This is repeated until the AEL is not exceeded or the laser product is assigned to
Class 4.
The system must be evaluated in accordance with the standard to insure that a reasonably
forseeable single fault cannot cause the laser to emit radiation higher than the AEL for the
assigned class. If this criterion is met, the laser classification is known.

Begin with Choose
Is laser YES
product and YES Class to
Wavelength
continuous Determine
supplied evaluate –
known?
time base
wave?
information start with
Class 1
NO
NO
Angular
YES
Determine subtense, NO
Refer to Pulsed
wavelength acceptance
Classification
angle known?
Flowchart
Determine angular
subtense,
acceptance angle or
assume small
source (C = 1)
Determine AEL
(See Note 3)
Determine
measurement
time base
conditions and
limits
(See Note 1, 2)
Choose NO
Accessible Use manufacturer’s
another Class emission less
output data or
(See Note 3) than AEL?
measure output data
NO
YES
YES Satisfies
Can be
Classification
single-
assigned to
known
fault?
chosen
IEC  2339/11
Figure 1 – Continuous wave laser classification flow

– 12 – TR 60825-13  IEC:2011(E)

Begin with
Choose Class
YES Wavelength,
product and YES
Is laser
to evaluate –
PW, PRF
supplied Determine
pulsed or
start with
known?
information time base
scanned?
Class 1
NO NO
Refer to CW
Angular
Determine
YES
Classificatio NO
subtense,
wavelength,
n Flowchart
acceptance
PW and PRF
angle known?
Determine angular
subtense,
acceptance angle or
assume small source
Determine AEL (C = 1)
measurement See Note 3
Determine
conditions and
time base
limits
(See Note 1, 2)
Select one of
conditions in 8.3f) to
evaluate
Use
Choose
manufacturer’s
Accessible
another Class
output data or
emission less
(See Note 3)
measure output
than AEL?
NO
data
YES
Have all
NO
conditions of
8.3f) been
evaluated?
NO
YES
YES
Satisfies
Can be assigned
Classification
single-
to the chosen
known
fault?
Class
IEC  2340/11
Figure 2 – Pulsed laser classification flow
NOTE 1 There may be more than one condition to be met if a product is to be assigned a certain class. For
instance, in the wavelength region 400 nm – 600 nm, neither the thermal nor photochemical limit (each with its own
measurement conditions) should be exceeded for a class to apply. Also, if a product has a pulsed output, none of
the three limits (single pulse, pulse train and average power) may be exceeded.
NOTE 2 If using an extended source, the AEL will be a function of distance from the source. The most hazardous
distance must be used for classification.
NOTE 3 If Class 1 or Class 2 requirements are not satisfied, it is appropriate to evaluate product emission using
the Class 1M or Class 2M requirements. If a product emission satisfies the Class 1M or Class 2M requirements, it
is not necessary to satisfy the Class 3R requirements.
7 Parameters for calculation of accessible emission limits
7.1 Wavelength (λ)
7.1.1 Wavelength determination
It is usually not necessary to determine this parameter to great accuracy. In general,
biological hazards are not strong functions of wavelength. There are several exceptions (refer
to Figure 3):
TR 60825-13  IEC:2011(E) – 13 –
a) 302,5 nm – 315 nm region: over this range, the T and C parameters change
1 2
significantly;
b) 450 nm – 600 nm region: over this range, the photochemical hazard decreases by a factor
of 1 000;
c) 1 150 nm – 1 200 nm region: over this range, the thermal hazard decreases by a factor of
eight;
d) 400 nm: at wavelengths greater than 400 nm, the hazard is mainly retinal; at shorter
wavelengths, it is mainly non-retinal;
e) 1 400 nm; at wavelengths greater than 1 400 nm, the hazard is mainly non-retinal; at
shorter wavelengths, it is mainly retinal.

Rapid change of the
AEL with
wavelength
Retinal photochemical
hazard region
(thermal hazard exists
for sufficient exposure
for all wavelengths
above 400 nm)
Visible
Wavelength (nm)
200 400 600 800 1 000 1 200 1 600 1 800
1 400
Retinal hazard region
Additive hazard
region boundaries IEC  2341/11

Figure 3 – Important wavelengths and wavelength ranges
For a narrow laser line, a wavelength provided by the manufacturer will likely be all that is
necessary, and the remainder of 7.1 as well as 7.2 and 7.3 below need not be considered.
If the range of possible wavelengths (product-to-product variation) is a sizeable fraction of a),
b) or c) above, either the most hazardous (shortest) wavelength may be used, or the
wavelength may be measured for a given product.
In regions a), b) or c), a piece-wise summation may be required, determining the limit at
several wavelengths and weighting by the output associated with that wavelength. This is
discussed in detail below in subclauses 7.2.2 and 7.3.
Additive refers to hazards that must be considered together. For instance, multiple emissions
less than 400 nm, or between 400 nm and 1 400 nm, or greater than 1 400 nm are additive.
For spectrally broad or multiple emissions in each region, the hazards are additive, and a
piecewise summation must be performed, as described in item b) of 8.3 of the standard. If a
product emits wavelengths in two of these ranges (e.g., 700 nm and 1 500 nm), then the two
wavelengths should be considered separately using the relevant AELs for each wavelength.
For classification purposes, the higher class will apply.
For lasers whose possible range of output wavelength or output spectrum includes
wavelengths greater than 1 400 nm and/or less than 400 nm, special considerations should be
made with regard to the AEL. The hazards on either side of the boundary wavelengths are
different, and the effects are different. To be assigned a given class, the power or energy in
each spectral region must be less than each corresponding AEL.

– 14 – TR 60825-13  IEC:2011(E)
Measurement or determination of the wavelength parameter is fundamental to laser hazard
evaluations and laser classification. The wavelength must be identified to decide on which
type of power or energy meter is to be employed. Some radiometers have detector elements
that respond very efficiently in the visible and near-infrared, but have little to no responsivity
in the far-infrared or ultraviolet and vice versa. Additionally, the appropriate application of
exposure limits is dependant upon wavelength as well. In most cases, direct measurement of
the operating wavelength of a laser is not necessary. This is usually specified by the
manufacturer with more than a reasonable amount of certainty.
For lasers that can emit more than one wavelength, or emit near either limit of the retinal
hazard region, determination of the emission spectrum is of utmost importance. Measurement
of wavelength or spectral emission can be accomplished by techniques using a variety of
equipment. Optical spectrum analyzers and similar instruments, such as wavemeters, offer
the easiest operation. Most of these devices simply sample the beam and give a digital
readout of the wavelength or spectrum. Some have geometrical and field of view limitations,
but are usually very reliable. Monochromators, especially if manually operated, can be a little
more labour intensive and time consuming, but are also very dependable and accurate.
Optical filters, such as narrow band pass filters can also be considered as another option but
they do have some limitations. Employment of these filters requires prior knowledge of
approximately what wavelength is expected. Also, for multiple wavelength lasers or lasers
with a broad emission, use of filters for wavelength or spectral emission determination can be
quite cumbersome, if not futile.
7.1.2 Ocular hazard regions
The thermal hazard exists for sufficient exposure at all wavelengths above 400 nm.
The retinal photochemical hazard is only a consideration from 400 nm to 600 nm, and for
exposure times greater than 1 s.
The hazard regions are broken down as follows:
• 180 nm to 400 nm. The hazard is mainly photochemical and non-retinal for CW exposure
and thermal for pulsed exposure. (The standard does not address wavelengths shorter
than 180 nm);
• 400 nm to 600 nm. In this range, both thermal and photochemical hazards must be
considered. For the photochemical hazard, emission times of less than 10 s (or 1 s for the
wavelength region 400 to 484 nm with apparent sources between 1,5 and 82 mrad) need
not be considered;
• 400 nm to 1 400 nm. In this range, the retinal hazard region, the hazard to the retina
predominates;
• 1 400 nm to 1 mm. At wavelengths greater than 1 400 nm the penetration depth of the
radiation is much smaller than for wavelengths between 400 nm and 1 400 nm. The
hazard is thermal but mainly non-retinal.
7.2 Multiple wavelength sources
7.2.1 General
The term multiple wavelength sources refers to a source that emits radiation in two or more
discrete wavelengths. Multiple line lasers clearly fall into this category. These different
wavelengths may fall into different hazard regions of the spectrum resulting in different
biological effects and need to be accounted for independently. See 7.1.1, 7.1.2, and Figure 3.
Ultrashort pulse lasers can contain a relatively large wavelength bandwidth. The wavelength
bandwidth for these lasers should be evaluated with the procedure in 7.3 if the AEL or MPE
limit varies more than 10 % for the wavelength band of the laser pulse.

TR 60825-13  IEC:2011(E) – 15 –
7.2.2 Single hazard region
For several sources emitting simultaneously at different wavelengths whose radiation
produces the same type of hazard, a weighted sum must be used to determine whether the
product meets or exceeds the AEL for a given class. For a single wavelength the criterion
may be stated as:
If P < AEL,
meas
then the product does not exceed the class limit
where P is the measured power (or energy or other quantity specified), and AEL is the
meas
class power (or energy or other quantity specified) limit. This can be restated as:
If P / AEL < 1,
meas
then the product does not exceed the class limit.
In this form, this can be extended to two wavelengths:
If P (λ ) / AEL(λ ) + P (λ ) / AEL(λ ) < 1,
meas 1 1 meas 2 2
then the product does not exceed the class limit.
For more than two wavelengths, this can be extended to a general summation:
If Σ [P (λ ) / AEL(λ )] < 1,
meas i i
i = 1,2,3…
then the product does not exceed the class limit.
This only applies to one type of hazard at a time (i.e., photochemical and thermal hazards are
treated separately).
NOTE While the thermal hazard limit values are different for the visible range (400 nm to 700 nm) and the near
infrared range (70
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