SIST EN 61280-1-4:2010

Fibre optic communication subsystem test procedures - Part 1-4: General communication subsystems - Light source encircled flux measurement method (IEC 61280-1-4:2009)

This part of IEC 61280 is intended to characterize the encircled flux of two types of light sources: transmission light sources, which are usually coherent and substantially under-excite the mode volume of a multimode fibre, and measurement light sources, which are incoherent and excite most of the mode volume of a multimode fibre. This part of IEC 61280 sets forth a standard procedure for the collection of two-dimensional fibre optic nearfield greyscale data and subsequent reduction to one-dimensional data expressed as a set of three sampled parametric functions of radius from the fibre's optical centre. This revision of IEC 61280-1-4 continues to fulfil its original purpose, characterization of transmission light sources, which enables the accurate mathematical prediction of minimum guaranteed link length in 1 gigabit per second or greater fibre optic data communication systems. New to this revision is support for improved measurement precision of insertion loss in multimode fibre optic links through the characterization of measurement light sources. Estimation of the fibre core diameter is not an objective of this standard.

Lichtwellenleiter-Kommunikationsuntersysteme - Grundlegende Prüfverfahren - Teil 1-4: Allgemeine Kommunikationsuntersysteme - Verfahren zur Messung des begrenzten Lichtstroms einer Strahlungsquelle (IEC 61280-1-4:2009)

Procédures d'essai des sous-systèmes de télécommunication à fibres optiques - - Partie 1-4: Sous-systèmes généraux de télécommunication - Méthode de mesure du flux inscrit de la source lumineuse (CEI 61280-1-4:2009)

La CEI 61280-1-4:2009 définit une procédure standard consistant à collecter des données de niveaux de gris de champ proche de fibres optiques bidimensionnelles, puis à les réduire en données unidimensionnelles exprimées sous la forme d'un ensemble de trois fonctions paramétriques échantillonnées du rayon par rapport au centre optique de la fibre. La présente révision de la CEI 61280-1-4 satisfait ce but initial, la caractérisation des sources lumineuses de transmission, qui permet une prévision mathématique précise de la longueur minimum garantie de la liaison dans les systèmes de communication de données par fibres optiques de 1 gigabit par seconde ou plus. Une nouveauté de cette révision est l'amélioration de la précision des mesures des pertes d'insertion dans des liaisons à fibres optiques multimodales par la caractérisation des sources lumineuses de mesure.

Postopki preskušanja optičnega komunikacijskega podsistema - 1-4. del: Splošni komunikacijski podsistemi - Merilna metoda za pretok, ki ga obkroža svetlobni vir (IEC 61280-1-4:2009)

Ta del IEC 61280 je namenjen opredelitvi pretoka, ki ga obkrožata dve vrsti svetlobnega vira: transmisijski svetlobni viri, ki so običajno koherentni in vzbujajo manjše število rodov večrodovnega vlakna, in merilni svetlobni viri, ki so nekoherentni in vzbujajo večino rodov večrodovnega vlakna. Ta del IEC 61280 določa standardni postopek za zbiranje črno-belih dvodimenzionalnih bližnjih podatkov optičnih vlaken in kasnejše zmanjševanje na enodimenzionalne podatke, izražene kot zaporedje treh vzorčenih parametričnih funkcij premera od optične sredine vlakna. Ta revizija IEC 61280-1-4 še naprej izpolnjuje svoj prvotni namen, opredelitev lastnosti transmisijskih svetlobnih virov, kar omogoča natančno matematično napovedovanje minimalne zagotovljene dolžine povezave pri sistemih za podatkovno komunikacijo z optičnimi vlakni s hitrostjo 1 gigabita na sekundo ali več. Novost v tej reviziji je podpora boljši natančnosti merjenja notranje izgube pri večrodovnih povezavah iz optičnih vlaken preko opredelitve lastnosti merilnih svetlobnih virov. Ocena premera sredice vlakna ni namen tega standarda.

General Information

• Status: Published
• Publication Date: 04-Mar-2010
• ICS: 33.180.01 - Fibre optic systems in general
• Technical Committee: MOC - Mobile Communications
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 24-Feb-2010
• Due Date: 01-May-2010
• Completion Date: 05-Mar-2010
• Ref Project: EN 61280-1-4:2010 - Fibre optic communication subsystem test procedures - Part 1-4: General communication subsystems - Light source encircled flux measurement method

Relations

• Replaces: SIST EN 61280-1-4:2004 - Fibre optic communication subsystem test procedures -- Part 1-4: General communication subsystems - Collection and reduction of two-dimensional nearfield data for multimode fibre laser transmitters
• Effective Date: 01-Apr-2010
• Replaced By: SIST EN IEC 61280-1-4:2023 - Fibre optic communication subsystem test procedures - Part 1-4: General communication subsystems - Light source encircled flux measurement method (IEC 61280-1-4:2023)
• Effective Date: 08-Feb-2022
• Replaces: SIST EN 61280-1-4:2004 - Fibre optic communication subsystem test procedures -- Part 1-4: General communication subsystems - Collection and reduction of two-dimensional nearfield data for multimode fibre laser transmitters
• Effective Date: 13-May-2010
• Replaces: SIST EN 61280-1-4:2004 - Fibre optic communication subsystem test procedures -- Part 1-4: General communication subsystems - Collection and reduction of two-dimensional nearfield data for multimode fibre laser transmitters
• Effective Date: 28-Jan-2023

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN 61280-1-4:2010
01-april-2010
1DGRPHãþD
SIST EN 61280-1-4:2004
3RVWRSNLSUHVNXãDQMDRSWLþQHJDNRPXQLNDFLMVNHJDSRGVLVWHPDGHO6SORãQL
NRPXQLNDFLMVNLSRGVLVWHPL0HULOQDPHWRGD]DSUHWRNNLJDRENURåDVYHWOREQLYLU
,(&
Fibre optic communication subsystem test procedures - Part 1-4: General
communication subsystems - Light source encircled flux measurement method (IEC
61280-1-4:2009)
Lichtwellenleiter-Kommunikationsuntersysteme - Grundlegende Prüfverfahren - Teil 1-4:
Allgemeine Kommunikationsuntersysteme - Verfahren zur Messung des begrenzten
Lichtstroms einer Strahlungsquelle (IEC 61280-1-4:2009)
Procédures d'essai des sous-systèmes de télécommunication à fibres optiques - - Partie
1-4: Sous-systèmes généraux de télécommunication - Méthode de mesure du flux inscrit
de la source lumineuse (CEI 61280-1-4:2009)
Ta slovenski standard je istoveten z: EN 61280-1-4:2010
ICS:
33.180.01 6LVWHPL]RSWLþQLPLYODNQLQD Fibre optic systems in
VSORãQR general
SIST EN 61280-1-4:2010 en,fr
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 61280-1-4:2010

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SIST EN 61280-1-4:2010

EUROPEAN STANDARD
EN 61280-1-4

NORME EUROPÉENNE
February 2010
EUROPÄISCHE NORM

ICS 33.180.01 Supersedes EN 61280-1-4:2003


English version


Fibre optic communication subsystem test procedures -
Part 1-4: General communication subsystems -
Light source encircled flux measurement method
(IEC 61280-1-4:2009)


Procédures d'essai des sous-systèmes  Lichtwellenleiter-
de télécommunication à fibres optiques - Kommunikationsuntersysteme -
Partie 1-4: Sous-systèmes généraux Grundlegende Prüfverfahren -
de télécommunication - Teil 1-4: Allgemeine
Méthode de mesure du flux inscrit Kommunikationsuntersysteme -
de la source lumineuse Verfahren zur Messung des begrenzten
(CEI 61280-1-4:2009) Lichtstroms einer Strahlungsquelle
(IEC 61280-1-4:2009)




This European Standard was approved by CENELEC on 2010-02-01. CENELEC members are bound to comply
with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard
the status of a national standard without any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the Central Secretariat or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CENELEC member into its own language and notified
to the Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus,
the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy,
Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia,
Spain, Sweden, Switzerland and the United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Central Secretariat: Avenue Marnix 17, B - 1000 Brussels


© 2010 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 61280-1-4:2010 E

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SIST EN 61280-1-4:2010
EN 61280-1-4:2010 - 2 -
Foreword
The text of document 86C/920/FDIS, future edition 2 of IEC 61280-1-4, prepared by SC 86C, Fibre optic
systems and active devices, of IEC TC 86, Fibre optics, was submitted to the IEC-CENELEC parallel vote
and was approved by CENELEC as EN 61280-1-4 on 2010-02-01.
This European Standard supersedes EN 61280-1-4:2003.
The significant technical changes with respect to EN 61280-1-4:2003 are described in the introduction.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN and CENELEC shall not be held responsible for identifying any or all such patent
rights.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2010-11-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2013-02-01
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 61280-1-4:2009 was approved by CENELEC as a European
Standard without any modification.
In the official version, for Bibliography, the following notes have to be added for the standards indicated:
IEC 60793-1-20 NOTE  Harmonized as EN 60793-1-20.
IEC 60793-1-41 NOTE  Harmonized as EN 60793-1-41.
__________

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SIST EN 61280-1-4:2010
- 3 - EN 61280-1-4:2010

Annex ZA
(normative)

Normative references to international publications
with their corresponding European publications

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.

NOTE  When an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD
applies.

Publication Year Title EN/HD Year

IEC 60793-2-10 - Optical fibres - EN 60793-2-10 -
Part 2-10: Product specifications - Sectional
specification for category A1 multimode fibres


IEC 60825-1 - Safety of laser products - EN 60825-1 -
Part 1: Equipment classification and
requirements


IEC 61745 1988 End-face image analysis procedure for the - -
calibration of optical fibre geometry test sets

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SIST EN 61280-1-4:2010

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SIST EN 61280-1-4:2010

IEC 61280-1-4
®
Edition 2.0 2009-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside


Fibre optic communication subsystem test procedures –
Part 1-4: General communication subsystems – Light source encircled flux
measurement method

Procédures d’essai des sous-systèmes de télécommunication à fibres
optiques –
Partie 1-4: Sous-systèmes généraux de télécommunication – Méthode de
mesure du flux inscrit de la source lumineuse

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
W
CODE PRIX
ICS 33.180.01 ISBN 2-8318-1070-6
® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale

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SIST EN 61280-1-4:2010
– 2 – 61280-1-4 © IEC:2009
CONTENTS
FOREWORD.4
0 Introduction .6
0.1 General .6
0.2 Changes from previous edition .6
0.3 Assumptions applicable to the characterization of data sources .6
0.4 Assumptions applicable to the characterization of measurement sources .6
1 Scope.7
2 Normative references .7
3 Terms and definitions .7
4 Symbols .8
5 Apparatus.9
5.1 Common apparatus .9
5.1.1 General .9
5.1.2 Computer .10
5.1.3 Image digitizer.10
5.1.4 Detector .10
5.1.5 Magnifying optics.11
5.1.6 Attenuation .11
5.1.7 Micropositioner (optional) .11
5.1.8 Input port.12
5.1.9 Calibration light source.12
5.2 Transmission source apparatus .12
5.2.1 General .12
5.2.2 Test jumper assembly.13
5.2.3 Fibre shaker .13
5.3 Measurement source apparatus .14
6 Sampling and specimens.14
7 Geometric calibration .15
8 Measurement procedure.15
8.1 Safety .15
8.2 Image acquisition .15
8.2.1 Raw image acquisition.15
8.2.2 Dark image acquisition .16
8.2.3 Corrected image .16
8.3 Optical centre determination.16
8.3.1 General .16
8.3.2 Centroid image .16
8.3.3 Centroid computation .17
8.4 Test source image acquisition .17
9 Computation of encircled flux .17
9.1 Computation of radial data functions .17
9.2 Integration limit and baseline determination.19
9.2.1 Integration limit.19
9.2.2 Baseline determination .19
9.2.3 Baseline subtraction .19

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SIST EN 61280-1-4:2010
61280-1-4 © IEC:2009 – 3 –
9.3 Computation of encircled flux .19
10 Results .20
10.1 Information available with each measurement .20
10.2 Information available upon request.20
11 Specification information .20
Annex A (informative) Measurement sensitivity considerations .22
Annex B (informative) Theory of geometric calibration using the micropositioner .27
Annex C (normative) Procedure for geometric calibration using the micropositioner.32
Bibliography.34

Figure 1 – Apparatus block diagram.10
Figure 2 – Typical set-up for transmission source measurement .13
Figure 3 – Fibre shaker example.14
Figure 4 – Pixel and ring illustration.18
Figure A.1 – Core images from instrument A and instrument B .22
Figure A.2 – Compressed core images from instrument A and instrument B.22
Figure A.3 – Intensity versus radius for Instruments A and B .23

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SIST EN 61280-1-4:2010
– 4 – 61280-1-4 © IEC:2009
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

FIBRE OPTIC COMMUNICATION SUBSYSTEM TEST PROCEDURES –

Part 1-4: General communication subsystems –
Light source encircled flux measurement method


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
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
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
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
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
members of its technical committees and IEC National Committees for any personal injury, property damage or
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.
International Standard IEC 61280-1-4 has been prepared by subcommittee 86C: Fibre optic
systems and active devices, of IEC technical committee 86: Fibre optics.
This second edition cancels and replaces the first edition published in 2003. This second
edition constitutes a technical revision. The significant technical changes with respect to the
previous edition are described in the introduction.
The text of this standard is based on the following documents:
FDIS Report on voting
86C/920/FDIS 86C/932/RVD

Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.

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SIST EN 61280-1-4:2010
61280-1-4 © IEC:2009 – 5 –
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts of the IEC 61280 series can be found, under the general title Fibre optic
communication subsystem test procedures, 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.

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 publication using a colour printer.

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SIST EN 61280-1-4:2010
– 6 – 61280-1-4 © IEC:2009
0 Introduction
0.1 General
This part of IEC 61280 is used to measure the encircled flux of a multimode light source.
Encircled flux is a measure, as a function of radius, of the fraction of the total power radiating
from a multimode optical fibre’s core.
The basic approach is to collect 2D nearfield data using a calibrated camera, and to
mathematically convert the 2D data into three normalized functions of radial distance from the
fibre’s optical centre. The three functions are intensity, incremental flux and encircled flux.
Intensity has dimension optical power per area; incremental flux has dimension power per
differential of radius; and encircled flux has dimension total optical power, all three being
functions of radius.
These three radial functions are intended to characterize fibre optic laser sources either for
use in mathematical models predicting the minimum guaranteed length of a communications
link, or to qualify a light source to measure insertion loss in multimode links.
0.2 Changes from previous edition
This edition of the standard differs from its predecessor in both scope and content. Many of
the content changes improve the measurement precision. Several changes have been made
to the computation procedure:
• the integration methodology of the radial functions was simple summation, and is now
specified to use trapezoidal integration or other higher-order techniques (see 9.3);
• a baseline subtraction step is specified to improve immunity to DC drifts (see 9.2.2 and
9.2.3);
• the ring width parameter is explicitly specified (see 9.2.1);
• the integration limit is specified (see 9.3).
The geometric calibration of the apparatus microscope now specifies either (depending on the
application) the methodology of IEC 61745 or the original technique using the
micropositioning stage (see Clause 7). Pixel sensitivity uniformity correction is now optional.
0.3 Assumptions applicable to the characterization of data sources
The 50-μm or 62,5-μm core near-parabolic graded-index multimode fibre used as the “test
jumper assembly” is treated as if it possessed perfect circular symmetry about its optical
centre, as asymmetries in the launched optical flux distributions will dominate any
lopsidedness of the test jumper assembly. It is further assumed that all cladding modes will be
stripped by passage through the specified ten metres or more of fibre. The modes of a mode
group need not carry equal flux. (In fact, with such short fibres, one thousand metres or less,
unequal distribution of flux in the modes of a group is the norm, not the exception.)
0.4 Assumptions applicable to the characterization of measurement sources
Measurement sources are assumed to be sufficiently broadband and incoherent that speckle
is not a problem, and to have a sufficiently symmetrical nearfield distribution that the
truncated centroid of that nearfield indicates the location of the optical centre of the fibre with
sufficient accuracy for the purposes of this standard.

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SIST EN 61280-1-4:2010
61280-1-4 © IEC:2009 – 7 –
FIBRE OPTIC COMMUNICATION SUBSYSTEM TEST PROCEDURES –

Part 1-4: General communication subsystems –
Light source encircled flux measurement method



1 Scope
This part of IEC 61280 is intended to characterize the encircled flux of two types of light
sources: transmission light sources, which are usually coherent and substantially under-excite
the mode volume of a multimode fibre, and measurement light sources, which are incoherent
and excite most of the mode volume of a multimode fibre.
This part of IEC 61280 sets forth a standard procedure for the collection of two-dimensional
fibre optic nearfield greyscale data and subsequent reduction to one-dimensional data
expressed as a set of three sampled parametric functions of radius from the fibre’s optical
centre. This revision of IEC 61280-1-4 continues to fulfil its original purpose, characterization
of transmission light sources, which enables the accurate mathematical prediction of minimum
guaranteed link length in 1 gigabit per second or greater fibre optic data communication
systems. New to this revision is support for improved measurement precision of insertion loss
in multimode fibre optic links through the characterization of measurement light sources.
Estimation of the fibre core diameter is not an objective of this standard.
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 60793-2-10, Optical fibres – Part 2-10: Product specifications – Sectional specification for
category A1 multimode fibres
IEC 60825-1, Safety of laser products – Part 1: Equipment classification and requirements
IEC 61745:1988, End-face image analysis procedure for the calibration of optical fibre
geometry test sets
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
calibration light source
light source used to find the optical centre of a multimode fibre
3.2
centroid image
image used to determine the optical centre of the multimode fibre core

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SIST EN 61280-1-4:2010
– 8 – 61280-1-4 © IEC:2009
3.3
corrected image
image which has had a dark image subtracted from it and whose elements have had
uniformity correction applied
3.4
dark image
image taken with the measured light source either turned off or not installed in the input port.
Stray light and electrical signals of the detection system will remain in the dark image
3.5
image
two-dimensional rectangular array of numbers whose elements are pixels and whose pixel
values linearly correspond to the optical power falling on the pixels
3.6
light source
something that emits light that is coupled into a fibre, the output of which can be measured
(can be a calibration light source, a transmission light source or a light source used for
attenuation measurements)
3.7
measurement light source
light source intended to be used in the measurement of attenuation
3.8
nominal core radius
half the nominal core diameter of the multimode fibre to be measured
3.9
ring smoothing
technique to reduce the two dimensional near field image into a 1-D near field intensity profile
while cancelling the effects of the periodic spacing of imager pixels of finite area
3.10
transmission light source
light source used to transmit digital data over multimode fibre optic links
3.11
uniformity correction
process to correct the sensitivity of a pixel so that it performs substantially like an average
pixel
3.12
valid pixel
optical detection element in the detector matrix whose sensitivity, when corrected, is within
5 % of the mean sensitivity of the average conversion efficiency of the detector
4 Symbols
B  the baseline intensity. This value is determined from a region of the computed near
field just outside the core boundary.
D  the distance from the centre of the centroid image to the nearest boundary of the
image.
D , D , D , D the set of distances from the centre of the centroid image to, respectively, the
L R T B
left, right, top and bottom boundaries of the image. The minimum of this set is
used to compute D.

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SIST EN 61280-1-4:2010
61280-1-4 © IEC:2009 – 9 –
EF(i) the encircled flux vector.
i  the index parameter used in the parametric result vectors R(i), I(i) and EF(i) .
I the matrix of pixel intensities of a dark image as measured by the detector and
dark
digitizer.
I the matrix of pixel intensities of the light source, before correction, as measured by the
raw
detector and image digitizer.
I near-field intensity matrix. This is a matrix of pixel intensities, based on I , as
r,c raw
measured by the detector and corrected using U and I
dark.
I(i) the ring-smoothed intensity vector, each element being the arithmetic average of the
set of radial coordinates of all the pixels in a given ring.
N the number of rings used to compute the 1-D near field.
R
N the number of rows in an image. All columns in an image have the same number of
r
rows.
N the number of columns in an image. All rows in an image have the same number of
c
columns.
P the most intense valid pixel in the centroid image.
Max
P the least intense valid pixel in the centroid image.
Min
R the radial coordinate, in μm, of the centre of any pixel, referenced to the optical centre
X ,Y .
0 0
R(i) the ring-smoothed radial vector, each element being the arithmetic average of the radii
th
of all the pixels in the i ring.
S the column-weighted summation of all pixel intensities greater than T in the centroid
c
image.
S (i) the intensity summation vector used in ring smoothing.
I
S the summation of all pixel intensities greater than T in the centroid image.
P
S (i) the pixel counting vector used in ring smoothing.
N
S (i) the radius summation vector used in ring smoothing.
R
S the row-weighted summation of all pixel intensities greater than T in the centroid
r
image.
T the threshold used to determine which pixels in the centroid image will be used to
determine the optical centre. All pixels greater than or equal to T are used to compute
the centroid.
U the sensitivity correction matrix, applied to a dark-subtracted image to reduce non-
r,c
uniformity of the detector’s pixel-to-pixel conversion efficiency.
W the half-width, in μm, of the rings used to compute the 1-D near field.
X the x-axis (column) location of the centre of the centroid image.
0
Y the y-axis (row) location of the centre of the centroid image.
0
5 Apparatus
5.1 Common apparatus
5.1.1 General
The Figure 1 below shows an apparatus block diagram.

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SIST EN 61280-1-4:2010
– 10 – 61280-1-4 © IEC:2009
Collimating
3
region
Computer
Attenuat
...