IEC TR 60825-13:2006

TECHNICAL IEC
REPORT TR 60825-13
First edition
2006-08
Safety of laser products –
Part 13:
Measurements for classification
of laser products
Reference number
IEC/TR 60825-13:2006(E)
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TECHNICAL IEC
REPORT TR 60825-13
First edition
2006-08
Safety of laser products –
Part 13:
Measurements for classification
of laser products
 IEC 2006  Copyright - all rights reserved
No part of this publication may be reproduced or utilized in any form or by any means, electronic or
mechanical, including photocopying and microfilm, without permission in writing from the publisher.
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Telephone: +41 22 919 02 11 Telefax: +41 22 919 03 00 E-mail: inmail@iec.ch Web: www.iec.ch
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International Electrotechnical Commission
МеждународнаяЭлектротехническаяКомиссия
For price, see current catalogue

– 2 – TR 60825-13  IEC:2006(E)
CONTENTS
FOREWORD.3

1 Scope.5
2 Normative references .5
3 Terms and definitions .5
4 Applicability.7
4.1 General .7
4.2 Initial considerations .7
5 Instrumentation requirements .8
6 Classification flow.8
7 Parameters for calculation of accessible emission limits .12
7.1 Wavelength (λ).12
7.2 Multiple wavelength sources.13
7.3 Spectrally broad sources .14
7.4 Source temporal behaviour.16
7.5 Angular subtense (α).18
7.6 Emission duration.26
7.7 Measurement conditions.26
7.8 Scanning beams.27

Annex A (informative) Large source classification example .32

Bibliography.37

Figure 1 – Continuous wave laser classification flow.10
Figure 2 – Pulsed laser classification flow.11
Figure 3 – Important wavelengths and wavelength ranges .12
Figure 4 – Pulse duration definition.17
Figure 5 – Flat-topped and irregular pulses.18
Figure 6 – Examples of angular subtense .19
Figure 7 – Location of beam waist for a Gaussian beam .20
Figure 8 – Source measurement geometries .24
Figure 9 – Linear array apparent source size .25
Figure 10 – Effective angular subtense of a simple non-circular source .26
Figure 11 – Imaging a stationary apparent source located beyond the scanning beam
vertex .28
Figure 12 – Imaging a scanning apparent source located beyond the scanning beam
vertex .28

Table 1 – Reference points .20
Table 2 – Four source array.23

TR 60825-13  IEC:2006(E) – 3 –
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
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2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
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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.
The text of this technical report is based on the following documents:
Enquiry draft Report on voting
76/332/DTR 76/345/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.

– 4 – TR 60825-13  IEC:2006(E)
This technical report is to be used in conjunction with IEC 60825-1:1993 and its Amendment 1
(1997) and Amendment 2 (2001), referred to in this report as “the standard”.
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 maintenance result 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.

TR 60825-13  IEC:2006(E) – 5 –
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 (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 documents are 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 60825-1:1993, Safety of laser products – Part 1: Equipment classification, requirements
1)
and user’s guide
Amendment 1 (1997)
Amendment 2 (2001)
IEC 61040, Power and energy measuring detectors, instruments and equipment for laser
radiation
ISO 11554, Optics and optical instruments – Lasers and laser-related equipment – Test
methods for laser beam power, energy and temporal characteristics
3 Terms and definitions
For the purposes of this document, the terms and definitions contained in IEC 60825-1 as well
as the following apply.
3.1
angular velocity
speed of a scanning beam in radians per second
___________
1)
There exists a consolidated edition (1.2) of IEC 60825-1 (1993), including its Amendment 1 (1997) and
Amendment 2 (2001).
– 6 – TR 60825-13  IEC:2006(E)
3.2
beam profile
the irradiance distribution of a beam cross-section
3.3
beam waist
the minimum diameter of an axis-symmetric beam. For non-symmetric beams, there may be a
beam waist along each major axis, each located at a different distance from the source
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
the 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
a profile of a laser beam which is operated in the lowest transverse mode, TEM
NOTE A Gaussian beam profile may also be produced by passing non-TEM laser beams through beam shaping
optical elements.
3.7
measurement aperture
the 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
the number of pulses occurring per second, expressed in hertz (Hz)
3.9
Q-switch
a 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
a laser that emits short, high-power pulses by means of a Q-switch
3.11
Rayleigh distance
Z
r
0,5
the distance from the beam waist where the beam diameter has increased by a factor of 2
for Gaussian or near-Gaussian beam profiles
NOTE Rayleigh distance is often referred to as the confocal parameter.
3.12
responsivity
R
the output of a detector expressed as R = O/I, where O is the detector’s electrical output and I
is the optical power or energy input

TR 60825-13  IEC:2006(E) – 7 –
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 IEC 60825-1 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 IEC 60825-1, 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 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.
Measurements of scanned or modulated CW radiation at a fixed location also result 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 IEC 60825-1 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
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 the
configuration(s) of the product that are intended during all operating conditions, including
maintenance, service, and single fault conditions must be known. 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.
– 8 – TR 60825-13  IEC:2006(E)
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 IEC 60825-1 when measurements are needed. In many
cases actual radiometric measurements may not be necessary, and compliance with the
requirements of IEC 60825-1 can be determined from an analysis of a well-characterised
source and the design of the actual product.
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.
5 Instrumentation requirements
Measurement instruments to be used shall comply with the latest edition of IEC 61040 (Power
and energy measuring detectors, instruments and equipment for laser radiation). 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 precision 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.
Calibrations should be traceable to national standards.
Tests for the determination of measurement uncertainties of the instrument shall be done
according to IEC 61040.
For measurement uncertainties of CCD arrays and cameras see ISO 11554.
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.

TR 60825-13  IEC:2006(E) – 9 –
Tables 1 to 4 of IEC 60825-1 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
“Notes to Tables 1 to 4” of 9.3 of IEC 60825-1.
The classification flow is illustrated in Figures 1 and 2.
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.
Which class or classes are of interest must be determined. 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, and Class 2M might
be considered.
Next, the classification time base must be determined. This can be determined in terms of
default values (8.4e) in the standard), or determined from the definition of the T parameter
(Notes to Tables 1 to 4 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 1 to 4 in the
standard containing the formula or formulas of interest. The parameters used in the formulas
will determine what other parameters need to be determined. They include, primarily,
apparent source size (or the angular subtense equivalent, α), and the measurement
acceptance angle γ for the visible photochemical hazard. Generally, only simple extended
p
sources are addressed in this document. Considering the source to be a small source and
setting C = 1 is a conservative estimate if the apparent source size is not known.
Next, the measurement conditions must be determined (9.3 and Table 10 in the standard) and
AEL (Tables 1 to 4 in the standard). For a pulsed laser, several conditions given in 8.4f) 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 verified 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 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.

– 10 – TR 60825-13  IEC:2006(E)

Begin with
Choose Class to
Is laser YES
YES
product and
Wavelength evaluate –start Determine
continuous
supplied
known? with Class 1 time base
wave?
information
NO NO
Angular
YES
Refer to Pulsed NO
Determine
subtense,
Classification
wavelength
acceptance angle
Flowchart
known?
Determine angular
subtense,acceptance
angle or assume
Determine AEL
small source (C = 1)
Determine
measurement
time base
conditions and
limits (See Note 1)
Use
Choose another Accessible manufacturer’s
NO
Class emission less output data or

(See Note 2) than AEL? measure output

data
NO
YES
YES
Satisfies Can be assigned
Classification
single-fault? to chosen class
known
IEC  1466/06
Figure 1 – Continuous wave laser classification flow

TR 60825-13  IEC:2006(E) – 11 –

Begin with
Choose class to
Is laser
YES
product and YES
Wavelength,
evaluate – start
pulsed or Determine
supplied
PW, PRF
with Class 1
scanned? time base
information
known?
NO NO
Refer to CW
Determine
Angular
YES
Classification
NO
wavelength, PW
subtense,
Flowchart
and PRF
acceptance angle
known?
Determine angular
subtense, acceptance
angle or assume
Determine AEL
small source (C = 1)
measurement
Determine
conditions and
time base
limits (See Note 1)
Select one of
conditions in 8.4f)
to evaluate
Use
Choose another Accessible
NO
manufacturer’s
Class emission less
output data or
(See Note 2) than AEL?
measure output
data
YES
Have all
NO
conditions
of 8.4f) been
evaluated?
NO
YES
Can be assigned
Classification YES
Satisfies
to the chosen
known
single-fault?
Class
IEC  1467/06
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 – 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 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.

– 12 – TR 60825-13  IEC:2006(E)
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, optical
hazards are not strong functions of wavelength. There are several exceptions (refer to
Figure 3):
a) 302,4 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 Region
Wavelength  nm
200 400 600 800 1 000 1 200 1400 1 600 1 800
Retinal hazard region
Additive hazard
IEC  1468/06
region boundaries
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 1),
2) or 3) above, either the most hazardous (shortest) wavelength may be used, or the
wavelength may be measured for a given product.
In regions 1), 2) or 3), 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 sections 7.2.1 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 area, the hazards are additive, and a
piecewise summation must be performed, as described in item b) of 8.4 of IEC 60825-1. 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.

TR 60825-13  IEC:2006(E) – 13 –
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.
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
The term multiple wavelength sources refers to sources that emit radiation in two or more
discrete wavelengths. Multiple line lasers clearly fall into this category.
Lasers that emit pulses shorter than 100 fs 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.
7.2.1 Single hazard region
For several sources 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

– 14 – TR 60825-13  IEC:2006(E)
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 (700 nm to 1 400 nm), the time bases (either the emission duration t or the calculated parameter T )
are the same. Thus, the summation formula above still applies.
7.2.2 Two or more hazard regions
If a product emits two different wavelengths, and they are not in the same hazard region (e.g.,
λ = 300 nm and λ = 430 nm), each wavelength is to be treated separately:
1 2
If P (λ ) < AEL(λ ) and P (λ ) < AEL(λ ),
meas 1 1 meas 2 2
then the product does not exceed the class limit
If either condition is not satisfied, comparison with the AEL of higher classes should be
considered.
7.3 Spectrally broad sources
Some lasers (e.g., ultrashort-pulse lasers) have an appreciable spectral width. The
implications of this are that classification may require assessment in more than one spectral
region.
7.3.1 Spectral regions with small variation of the AEL with wavelength
If the spectral output of the emitter does not include any of spectral regions 1), 2) or 3) or the
boundary wavelengths of 4) or 5) (see 7.1 above), the distribution can be approximated by a
single wavelength.
1) If the AEL does not vary with wavelength, any choice of wavelength within the emitter
spectrum is equivalent.
2) If the AEL varies slowly with wavelength, and the wavelength emitter spectrum is
contained within one spectral range in the limit table, the limit for the peak or centre of the
distribution can be calculated, including shorter wavelengths corresponding to 10 % of
peak irradiance of the distribution. If the AEL difference is less than about 1 %, the peak
or centre wavelength may be used. A conservative approach is to use the most restrictive
wavelength concerned.
7.3.2 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)
If the emitter has some or all of its spectral output in the three regions in which the limits vary
greatly with wavelength, two approaches may be used.
1) Calculate the AEL using the lower wavelength boundary for the appropriate region. Since
AELs for shorter wavelengths are almost always more restrictive than AELs for longer
wavelengths, this simple and conservative approach may be used. However, this may
result in a limit that is overly restrictive. If the AEL calculated is acceptable (e.g., the
product is Class 1 with this assumption), no further calculations are needed.

TR 60825-13  IEC:2006(E) – 15 –
b) Calculate the sum of the measured power divided by the AEL as a function of wavelength.
Use the general summation in 7.2.1 above.
Assume, for instance, a source with a triangular spectral distribution, which has a lower
wavelength limit of 400 nm, a peak at 460 nm, and an upper wavelength limit of 520 nm.
The AEL from 400 nm to 450 nm is constant. Above 450 nm, the AEL increases
exponentially with the C factor. If:
P (400 nm < λ < 450 nm) / AEL (400 nm < λ < 450 nm) + Σ [P (λ )/AEL(λ )] < 1
meas meas i i
450<λ <520 nm
i
then the applicable AEL is not exceeded.
7.3.3 Spectral regions containing hazard-type boundaries (near 400 nm and
1 400 nm)
If the output spectral distribution includes a hazard region boundary (400 nm and 1 400 nm),
the output in each region is independent. Follow the procedure of 7.2.2 and 7.3.2 for each
spectral region, if necessary.
7.3.4 Very broad sources
A determination of power or energy per unit wavelength is required. If this information is not
available from the manufacturer, spectral measurements should be performed. It is beyond
the scope of this document to detail this here. Some information on broadband source
measurements is provided in CIE S009 – Photobiological Safety of Lamps and Lamp
Products.
If a laser product does not emit radiation below 315 nm, calculations can be simplified. The
following information is needed:
a) total power or energy between 315 nm and 400 nm measured as required by the standard
(P or Q );
a a
b) total power or energy between 400 nm and 700 nm measured as required by the standard
for thermal limits (P or Q );
b b
c) total power or energy between 400 nm and 450 nm measured as required by the standard
for photochemical limits (P or Q );
c c
d) power spectral distribution or energy spectral distribution from 450 nm to 600 nm
measured as required by the standard for photochemical limits (P (λ) or Q (λ));
d d
e) Power or energy spectral distribution from 700 nm to the long wavelength limit of the
distribution measured as required by the standard for thermal limits (P (λ)or Q (λ)).
e e
While the procedure applies to both power and energy, only power (P) will be used here.
– Choose an AEL. (Refer to Clause 9 of IEC 60825-1 for formulas and instructions on
calculating limits.)
– Calculate the ultraviolet limit AEL , and the ratio R = (P / AEL ).
a a a a
– Calculate the visible thermal limit AEL , and the ratio R = (P / AEL ).
b b b b
– Calculate the visible photochemical limit AEL for (400 nm < λ < 450 nm) and AEL (λ) for
c d
the range (450 nm < λ < 600 nm). Sum ratios:
R = P / AEL + Σ [P (λ ) / AEL (λ )]
cd c c d i d i
450 nm< λ <600 nm
i
– 16 – TR 60825-13  IEC:2006(E)
– Calculate the infrared thermal limit AEL (λ) for 700 nm to the long wavelength end of the
e
range. Sum ratios:
R = Σ [P (λ ) / AEL (λ )]
e e i e i
700 nm< λ <λ
i max
The product is assigned to the lowest laser Class for which ALL of the following are true:
R < 1,0;
a
R + R < 1,0; and
b e
R < 1,0
cd
7.4 Source temporal characteristics
If the product emits radiation continuously and with constant power, the analysis is
straightforward. The emission time must be determined, either specified in the standard as a
fixed duration, or specified by a calculated duration (i.e., T is a function of apparent source
size or source angular subtense). This allows the applicable AEL to be calculated. For such
products, the remainder of 7.4 need not be considered.
7.4.1 Sources with limited “ON” time
If a product can emit radiation only for a limited period of time that is less than the time basis
for that class specified in the standard, the shorter time can be used to calculate the
applicable AEL. Shorter emission times result in higher peak power limits. Note that it is
necessary to consider the AEL for all time durations up to the time base for classification.
7.4.2 Periodic or constant duty factor sources
Some products contain sources that produce a regular series of pulses, or an encoded
(irregular) series. The irregular series may be considered as a regular series if the maximum
duty factor is known. Duty factor here refers to the fraction or percentage of time the source is
emitting.
-6
For 3 microsecond long pulses at 120 pulses per second, the duty factor is 120 x 3 x 10 /1 or
0,036 %.
For an encoded series of pulses, using pulse train of 120 possible pulse positions of
3 microsecond long pulses every second with a 50 % encoding rate (50 % of the pulse
-6
positions contain a pulse, and 50 % do not), the duty factor is 0,5 x 120 x 3 x 10 /1 or
0,018 %.
Also, refer to Table 9 in IEC 60825-1 (time durations T below which pulse groups are
i
summed) for further information on how to calculate limits. The pulse rate, duty factor,
encoding duty factor and Table 9, along with the tables for the AELs, are needed to calculate
the effective pulse power and duration, as well as the effective pulse rate.
Three limits must be considered:
i) the limit for a single pulse, based on the pulse width;
ii) the limit for the average power for the specified or calculated classification time base;
iii) the limit for the average pulse energy from pulses within a pulse train, taking account
of C .
TR 60825-13  IEC:2006(E) – 17 –
Item f) of 8.4.of the standard specifies that the most restrictive of requirements i), ii), and iii)
be applied when determining the AEL for repetitively pulsed or modulated lasers for thermal
limits for wavelengths of 400 nm and above. Requirement iii) applies a correction factor to the
single pulse AEL based on the number of pulses emitted during the applicable time base or
T , whichever is shorter.
7.4.2.1 Pulse duration
The standard defines the pulse duration as the time increment measured between the half
peak power points at the leading and trailing edges of the pulse. Therefore, the duration of
interest is the time interval between the point, on the leading edge, at which the amplitude
reaches 50 % of the peak value and the point, on the trailing edge, that the amplitude returns
to the same value (see Figure 4).

2 4 6 8
t
IEC  1469/06
Figure 4 – Pulse duration definition
The pulse duration, t, can be accurately determined using a measurement instrument
consisting of a photosensitive detector and an oscilloscope or similar device. The measure-
ment instrument is subject to the following requirements.
a) The time response or frequency response of the entire measurement set-up must be
sufficient to measure the duration accurately.
b) The radiation to be measured must be sufficiently spread over the active area of the
detector such that there will be neither local saturation points nor local variations in
sensitivity of the detector.
c) The radiant exposure or irradiance of the radiation must not exceed the maximum
specified for the measurement instrument.
Single pulsed, Q-switched, mode-locked, and repetitively pulsed or scanning lasers all require
some knowledge of pulse duration in order to classify the product. In the case of scanned
radiation, pulse duration should be determined at all accessible positions in the scan pattern.
This is necessary because, depending on the type of deflector, the beam speed may not be
constant over the entire length of the scan line. For scanning products that incorporate a laser
operating in continuous wave (CW) mode, the pulse duration depends on beam diameter and
beam speed. For scanning products that incorporate a pulsed or modulated laser, the
modulation frequency, the beam diameter, and the scan velocity should be considered in
product
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