IEC TR 61341:2010

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
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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 t
...