IEC TR 61341:2010

Method of measurement of centre beam intensity and beam angle(s) of reflector lamps

IEC/TR 61341:2010 describes the method of measuring and specifying the centre beam intensity and the associated beam angle(s) of reflector lamps. It applies to:
- incandescent,
- tungsten halogen,
- gas-discharge and LED based reflector lamps for general lighting purposes. It does not apply to lamps for special purposes such as projection lamps. This second edition cancels and replaces the first edition published in 1994 and constitutes a technical revision. Due to the increasing use of reflector equipped LED lamps, the scope has been broadened and measurement conditions been included in order to take account of these lamps. Further, for easier understanding of the relation between the different axis and different intensities, two figures have been added. The luminous intensity distribution shall be reported instead of the centre beam intensity, if the latter is very low ("butterfly" distributions).

Méthode de mesure de l'intensité dans l'axe du faisceau et de l'angle (ou des angles) d'ouverture des lampes à réflecteur

La CEI/TR 61341:2010 décrit la méthode de mesure et de spécification de l'intensité dans l'axe du faisceau des lampes à réflecteur et de l'angle (ou des angles) d'ouverture dudit faisceau. Il s'applique aux lampes à réflecteur pour éclairage général des types suivants:
- à filament de tungstène,
- tungstène-halogène,
- à décharge et à LED. Il ne s'applique pas aux lampes spéciales, telles que les lampes de projection. Cette déuxième édition annule et remplace la première édition publiée en 1994 et constitue une révision technique. Suite à l'utilisation de plus en plus répandue des réflecteurs équipés de lampes à DEL, le domaine d'application a été élargi et des conditions de mesure ont été introduites pour tenir compte de ces lampes. En outre, deux figures ont été ajoutées pour une meilleure compréhension de la relation entre les différents axes et les différentes intensités. La répartition de l'intensité lumineuse doit être utilisée à la place de l'intensité dans l'axe du faisceau, si cette dernière est très faible (répartitions de type "butterfly").

General Information

• Status: Published
• Publication Date: 17-Feb-2010
• ICS: 29.140.20 - Incandescent lamps
• ICS: 33.060.30 - Radio relay and fixed satellite communications systems
• Technical Committee: SC 34A - Electric light sources
• Drafting Committee: WG 6 - TC 34/SC 34A/WG 6
• Current Stage: PPUB - Publication issued
• Start Date: 18-Feb-2010
• Completion Date: 31-May-2010

Standards Content (Sample)

IEC/TR 61341 ®
Edition 2.0 2010-02
TECHNICAL
REPORT
RAPPORT
TECHNIQUE
Method of measurement of centre beam intensity and beam angle(s) of reflector
lamps
Méthode de mesure de l’intensité dans l’axe du faisceau et de l'angle (ou des
angles) d’ouverture des lampes à réflecteur

IEC/TR 61341:2010
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IEC/TR 61341 ®
Edition 2.0 2010-02
TECHNICAL
REPORT
RAPPORT
TECHNIQUE
Method of measurement of centre beam intensity and beam angle(s) of reflector
lamps
Méthode de mesure de l’intensité dans l’axe du faisceau et de l'angle (ou des
angles) d’ouverture des lampes à réflecteur

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
K
CODE PRIX
ICS 29.140.20 ISBN 978-2-88910-508-3
– 2 – TR 61341 © IEC:2010
CONTENTS
FOREWORD.3
INTRODUCTION.5
1 Scope.6
2 Terms and definitions .6
3 Basic beam patterns.7
4 General conditions for measurement .7
5 Test arrangement .7
6 Measuring procedure.8
7 Specification of centre beam intensity and beam angle(s).9
Bibliography.10

Figure 1 – Relation between optical beam axis, geometrical-mechanical axis, peak
intensity and centre beam intensity.6
Figure 2 – Measurement of luminous intensity distribution .9
Figure 3 – Case where the centre beam intensity is smaller than 50 % of the peak
intensity.9

TR 61341 © IEC:2010 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
METHOD OF MEASUREMENT OF CENTRE BEAM INTENSITY
AND BEAM ANGLE(S) OF REFLECTOR LAMPS

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
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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 61341, which is a technical report, has been prepared by subcommittee 34A: Lamps, of
IEC Technical Committee 34: Lamps and related equipment.
The text of this technical report is based on the following documents:
Enquiry draft Report on voting
34A/1340/DTR 34A/1371/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.

– 4 – TR 61341 © IEC:2010
This second edition cancels and replaces the first edition published in 1994 and constitutes a
technical revision.
Due to the increasing use of reflector equipped LED lamps, the scope has been broadened
and measurement conditions been included in order to take account of these lamps. Further,
for easier understanding of the relation between the different axis and different intensities,
two figures have been added. The luminous intensity distribution shall be reported instead of
the centre beam intensity, if the latter is very low (“butterfly” distributions).
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
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.
TR 61341 © IEC:2010 – 5 –
INTRODUCTION
While the light output of lamps is normally characterized by the luminous flux, for reflector
lamps it is characterized by the centre beam intensity together with the beam angle(s).
This Technical Report gives guidance with regard to the measurement and interpretation of
these two basic characteristics of reflector lamps in order to allow the comparability of
reported values.
The adopted principles may help to classify lamps into beam angle groups; they are not
intended for the assessment of individual lamps.
For additional information, the reader is referred to the CIE Technical Report No 43,
describing the photometric characteristics of floodlight luminaires.

– 6 – TR 61341 © IEC:2010
METHOD OF MEASUREMENT OF CENTRE BEAM INTENSITY
AND BEAM ANGLE(S) OF REFLECTOR LAMPS

1 Scope
This Technical Report describes the method of measuring and specifying the centre beam
intensity and the associated beam angle(s) of reflector lamps.
It applies to incandescent, tungsten halogen and gas-discharge and LED based reflector
lamps for general lighting purposes. It does not apply to lamps for special purposes such as
projection lamps.
These recommendations relate to design testing of lamps only.
2 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
2.1
optical beam axis
the axis about which the luminous intensity distribution is substantially symmetrical
NOTE 1 The optical beam axis is not necessarily the same as the lamp axis through the lamp cap or the lamp
axis normal to a reference plane on the reflector (e.g. the rim), see Figure 1.
NOTE 2 It is assumed that only small (negligible) errors occur when symmetry is determined visually.
Center beam intensity
Mechanical/geometrical axis
Optical beam axis
Peak intensity
IEC  292/10
Figure 1 – Relation between optical beam axis, geometrical-mechanical axis,
peak intensity and centre beam intensity
2.2
peak intensity
I
p
the highest value of the luminous intensity regardless of whether or not it occurs on the
optical beam axis
NOTE The peak intensity is expressed in candela.
2.3
centre beam intensity
I
c
the value of the luminous intensity measured on the optical beam axis
NOTE The centre beam intensity is expressed in candela.

TR 61341 © IEC:2010 – 7 –
2.4
beam angle
the angle between two imaginary lines in a plane through the optical beam axis, such that
these lines pass through the centre of the front face of the lamp and through points at which
the luminous intensity is 50 % of the centre beam intensity
3 Basic beam patterns
The following beam patterns, as displayed on a surface normal to the optical beam axis, can
be distinguished.
– Symmetrical beam patterns, i.e. circular beams, for which measurements in any two
planes at right angles are sufficient.
– Asymmetrical beam patterns, for example oval or elliptical beams, which require
measurements in two planes coinciding with the major and minor axes (at right angles) of
the projected beam pattern.
– Irregular beam patterns, with more than one point of maximum intensity, which require
measurement in a number of planes.
4 General conditions for measurement
For incandescent and tungsten halogen lamps, prior to measurement, the lamp shall be aged
for approximately 1 h at its rated voltage. The measurements shall be made with a supply
voltage which is equal to the rated lamp voltage and which must be maintained constant
within ±0,5 %. If the lamp is marked with a voltage range, the test voltage shall be the mean
of the voltage range. The lamp shall not be rotated around the lamp axis during measurement.
For gas-discharge lamps, prior to measurement the lamp shall be aged for 100 h of normal
operation. During the measurement the appropriate reference ballast at rated input voltage
and frequency shall be used. The position of the gas-discharge lamp shall not be changed
during measurement.
For LED based reflector lamps, the measurement shall be made at an ambient temperature of
25 °C and at rated electrical operating conditions (voltage or current). The electrical operating
conditions shall be maintained constant within ± 0,5 % at thermal equilibrium. If there is a
temperature dependence of the luminous intensity of the LED based reflector lamp, the
position shall not be changed during measurement.
5 Test arrangement
The lamp is mounted in a suitable test facility, e.g. a photometer bench or directional
photometer.
The lamp is positioned at a suitable distance from the photo detector, i.e. the distance being
greater or equal to the shortest test distance which is compatible with the inverse square law
such that increasing the distance causes no practical change in the intensity.
The photo detector shall have spectral characteristics corrected according to the CIE spectral
luminous efficiency curve for photopic vision. The photo detector measures illuminance, which
is converted to luminous intensity by multiplying by the square of the distance.
The position of the photo detector relative to the lamp can be varied so that measurements
can be made over the field of illumination of the lamp. The distance between the lamp and the
photo detector should preferably be kept constant and the line perpendicular to the photo
detectors face plane should pass through the centre of the front face of the lamp. This test

– 8 – TR 61341 © IEC:2010
arrangement is based on the goniometer method of light intensity distribution measurement. If
the distance is not kept constant, suitable corrections shall be made.
NOTE 1 It is not necessary, or in some cases not possible, to achieve accurate alignment of the optical beam axis
in the measuring apparatus.
NOTE 2 Although specific details of a measuring system have been given, variations of technique are not
excluded. Should any discrepancy of results occur, the test method given in this report should be regarded as the
definitive technique.
6 Measuring procedure
6.1 The shape of the beam pattern, as projected on a matt screen, is viewed to determine
which basic beam pattern applies.
6.2 For lamps having a symmetrical or asymmetrical beam pattern with
– only one peak in the beam intensity distribution, or
– in case of more than one peak, with an angle between the peaks which is smaller than
10º,
the centre beam intensity is equal to the peak intensity.
The position of peak intensity is determined visually and its value, to be recorded as the
centre beam intensity (I ), is found by moving the lamp or photo detector while observing the
c
photo detector reading.
In each of the two planes (at right angles), the beam angle is determined by pivoting the lamp
or rotating the photo detector from one point of reading half centre beam intensity (I /2) to the
c
other point on the opposite side of the optical beam axis. For asymmetric beams, there may
be a need that before measurement the lamp is rotated around its axis in order to align with
the major and minor axes of the beam pattern.
6.3 For lamps having an irregular beam pattern with more than one peak in the luminous
intensity distribution, the following procedure shall be used, if both
– the angle between the maxima is 10º or larger, and
– the maxima have a luminous intensity at least 10 % higher than the lowest intensity
between them.
Measure the luminous intensity distribution (see Figure 2) and:
a) determine the point of peak intensity I ;
p
b) determine the positions on the distribution curve where the intensity is I /2;
p
c) bisect the angle between these two points;
d) determine the intensity value at the mid-point; to be recorded as the centre beam intensity
I ;
c
e) determine the positions on the distribution curve where the intensity is l /2;
c
f) the beam angle is determined from the curve at the two points where the intensity is l /2.
c
Measurements need to be made in at least 6 planes at regular intervals (or alternatively at
least 60 measurements in the field of illumination if plotting iso-candela diagrams).
NOTE Example: The (at least) 60 measurements may be achieved by at least
...