IEC 60825-4:2006/AMD2:2011

IEC 60825-4 ®
Edition 2.0 2011-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
AMENDMENT 2
AMENDEMENT 2
Safety of laser products –
Part 4: Laser guards
Sécurité des appareils à laser –
Partie 4: Protecteurs pour lasers

IEC 60825-4:2006/A2:2011
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IEC 60825-4 ®
Edition 2.0 2011-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
AMENDMENT 2
AMENDEMENT 2
Safety of laser products –
Part 4: Laser guards
Sécurité des appareils à laser –
Partie 4: Protecteurs pour lasers

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE PRICE CODE
G
CODE PRIX
ICS 31.260 ISBN 978-2-88912-431-2

– 2 – 60825-4 Amend. 2  IEC:2011
FOREWORD
This amendment has been prepared by IEC technical committee 76: Optical radiation safety
and laser equipment.
The text of this amendment is based on the following documents:
Enquiry draft Report on voting
76/428/CDV 76/442/RVC
Full information on the voting for the approval of this amendment can be found in the report
on voting indicated in the above table.
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• withdrawn,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.
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.
_____________
Replace the existing Annex D with the following new Annex D:

60825-4 Amend. 2  IEC:2011 – 3 –
Annex D
(normative)
Proprietary laser guard testing

D.1 General
This annex contains details of the test conditions to be adhered to and the documentation to
be supplied by manufacturers of proprietary laser guards.
It should be noted that it is inappropriate to use higher power lasers to simulate low power
laser parameters or use low powered lasers to simulate high powered, by changing irradiance
or by adjustment of the distance from the focal point, because beam quality and other
characteristics of the laser beam are likely to be different or unexpected. Manipulating
characteristics of lasers of a certain power level to make or extrapolate estimates of a laser in
a different level (higher or lower power) is not permitted.
The evidence of the tests described herein is relevant only for, and is limited to, the laser
parameters used. Thus the results of these tests should serve only for comparison of laser
guards.
–2
The protective exposure limit (PEL W·m ) shall be applicable only for the beam dimensions
at the guard used in the tests. These dimensions at the guard shall be stated by the laser
guard manufacturer because the PEL, which indicates protection, decreases as the laser
beam dimensions increase. If the PEL is exceeded, the guard can be damaged and eventually
disintegrates. For the purposes of this annex the protection time is the time interval from
initial irradiation of the front surface until the laser radiation emitting beyond the rear surface
exceeds the accessible emission limit (AEL) for Class 1 as defined in IEC 60825-1.
D.2 Test conditions
A variety of exposure limit tests with different materials and different lasers may cause non-
reproducible results that can lead to false interpretations for the protective exposure limit and
overestimated lifetime predictions of laser guards. Thus equal and comparable conditions for
repeated tests must be ensured to maintain the integrity of the results.
As part of ensuring the integrity of the results, effort shall be made to eliminate or at least
minimise systematic or other errors that may also result in false interpretations for the PEL or
overestimation of the guard lifetime. Such errors may arise from:
a) material: reflecting surfaces, where reflectivity changes through oxidation or
contamination;
b) laser: with high power lasers (e.g. multi-kilowatt lasers), especially those with good beam
quality (i.e. fibre lasers and disk lasers), reactions have been seen that have considerable
influence on the actual irradiance on the surface of the laser guards.
Thus during testing, it is important that no mechanical or physical effects (such as described
below) occur between the beam aperture and the point of incidence on the guard material that
adversely affect any optical properties. It is important to note that testing conditions should be
accurately replicated, otherwise the resultant PEL or protection times may not be reliably
reproduced.
Examples of effects that influence test results include but are not limited to:
• generation of fine metallic fume, whereby laser radiation is absorbed (e.g. thermal
blooming) or scattered (e.g. Mie effect) in the metallic fume;

– 4 – 60825-4 Amend. 2  IEC:2011
• change of the focal point (thermal induced focal shift), whereby there is a change of
the power density at the surface of the laser guard. These effects may reduce the laser
power on the sample under test;
• establishment of an equilibrium (i.e. thermal equilibrium or balance between, incident
and reflected or reemitted radiation) leading to a practically infinite PEL or protection
time in one test, while a repeated test under assumed equal conditions leads to a finite
PEL or protection time.
–2 –2
The tested exposure limit (W⋅m for CW lasers or J⋅m for pulsed lasers) shall be
determined by tests performed when irradiating at least six samples by irradiating one surface
of each sample. Each sample shall be of representative thickness and composition, having a
front test surface prepared to give worst case absorption to laser radiation. Dimensions of
these samples shall be not less than 3 times the beam diameter measured at the points where
the intensity distribution has decreased to a value of 1/e of the peak at the exposure location
(thereby guaranteeing that the radiant heat flow is taken into account). Structural connecting
elements shall only be included in the tests if they are necessary to ensure the construction
and integrity of the guard. In the case of non-circular beams, the geometry of the beam used
in the test shall be specified. Non-circular beams are those where the difference between the
major and the minor dimension is greater than 10 %. The tests shall be performed in both
pulsed and CW mode where pulsed and CW laser operation is possible as the pulsed
radiation may lead to different results.
NOTE 1 The parameters of pulsed radiation used in these tests should be representative of the parameters to be
used in any specified application.
NOTE 2 The geometry of the test beam is required to be specified because it affects the distribution of heat in the
sample.
NOTE 3 Particular care should be taken in the preparation of samples when testing laser guards using aluminium,
copper, stainless steel and materials with zinc coated surfaces. It has been observed for these and other similar
materials, the PEL and protection time is highly dependant on sample preparation and experimental setup that
affects the repeatability of the PEL and protection time measurements.
NOTE 4 The worst case absorption should take into account the reflectivity of the guard material and the changes
to the surface of the laser guard material over the foreseeable lifetime of the laser guard. However, the test plate
should not have been treated beforehand, in any possible way that could alter absorption conditions artificially,
except for accelerated natural reflectivity change of the guard material and the accelerated natural changes to the
surface of the laser guard material reasonably expected over the foreseeable lifetime of the laser guard.
Qualification test should be done in normal conditions for the laser shielding.”
If a sample holder is necessary for the tests, then its maximum overlap on the sample edge
shall not exceed 3 mm from the edge of the sample. The holding arrangement in contact
with the sample shall be thermally insulating (e.g. ceramic, etc.) compatible with use at the
temperatures generated.
The sample shall be normal (or tilted no more than ±3° to avoid retro-reflections) to the laser
beam with the beam axis centred on the sample at a distance ‘F1’ as shown in Figure D.1.
The distance F1 past the focal point shall be not greater than 3 times the focal length (F) of
the focusing lens. If for a specific application the guard is to be positioned at a distance less
than 3 times the focal length (F) away from the focal point, the minimum distance between the
focal point and the guard has to be taken as the distance F1.

Guard
Lens
F F1
IEC  1585/06
Figure D.1 – Simplified diagram of the test arrangement

60825-4 Amend. 2  IEC:2011 – 5 –
NOTE 5 Test should be performed with horizontally directed beam as shown in Figure D.1. If different beam
direction were used, mention the test arrangement regarding the beam direction in the qualification report.
The surface of the sample under test shall be sufficiently ventilated (e.g. by using a cross jet)
to ensure that the test surface and the space between the test sample and the beam shaping
optics remain clear of debris, fume, etc. during the period of the test. The ventilation shall
have the same effect as the air circulation in the intended application.
In addition, where there are multiple layers to the sample guard, all internal surfaces and
internal spaces shall be sufficiently ventilated (e.g. by using a cross jet) to ensure that all
surfaces remain clear of debris, fume etc. during the period of the test.
Cross jet on the front surface
and each multiple space
Laser beam
Guard system
F1
IEC  668/11
Figure D.2 – Simplified diagram of the ventila
...