Particle size analysis -- Image analysis methods

This document describes a method to transfer the images from particles having relative motion to binary images within practical systems, in which the particles in the images are individually separated. Images of moving particles are created by an optical image capture device. Effects of particle movement on the images are either minimized by the instrumentation or corrected by software procedures. This method is applicable to the particle images that are clearly distinguishable from static background. Further processing of the binary image, which is then considered as static, is described in ISOÂ 13322-1. A dynamic image analysis system is capable of measuring a higher number of particles compared to static image analysis systems. This document provides guidance on instrument qualification for particle size distribution measurements by using particulate reference materials. This document addresses the relative movement of the particles with respect to each other, the effect of particle movement on the image (motion blur), the movement and position along the optical axis (depth of field), and the orientation of the particles with respect to the camera.

Analyse granulométrique -- Méthodes par analyse d'images

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Published
Publication Date
16-Dec-2021
Current Stage
5060 - Close of voting Proof returned by Secretariat
Start Date
16-Sep-2021
Completion Date
15-Sep-2021
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FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 13322-2
ISO/TC 24/SC 4
Particle size analysis — Image analysis
Secretariat: BSI
methods —
Voting begins on:
2021-07-21
Part 2:
Voting terminates on:
Dynamic image analysis methods
2021-09-15
Analyse granulométrique — Méthodes par analyse d'images —
Partie 2: Méthodes par analyse d'images dynamiques
RECIPIENTS OF THIS DRAFT ARE INVITED TO
SUBMIT, WITH THEIR COMMENTS, NOTIFICATION
OF ANY RELEVANT PATENT RIGHTS OF WHICH
THEY ARE AWARE AND TO PROVIDE SUPPOR TING
DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
Reference number
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/FDIS 13322-2:2021(E)
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN-
DARDS TO WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS. ISO 2021
---------------------- Page: 1 ----------------------
ISO/FDIS 13322-2:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2021

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

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ii © ISO 2021 – All rights reserved
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ISO/FDIS 13322-2:2021(E)
Contents Page

Foreword ..........................................................................................................................................................................................................................................v

Introduction ................................................................................................................................................................................................................................vi

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms, definitions and symbols ............................................................................................................................................................ 1

3.1 Terms and definitions ....................................................................................................................................................................... 1

3.2 Symbols ......................................................................................................................................................................................................... 5

4 Principle ........................................................................................................................................................................................................................ 6

4.1 Key components of a dynamic image analyser............................................................................................................ 6

4.2 Illumination ............................................................................................................................................................................................... 7

4.2.1 Time performance .......................................................................................................................................................... 7

4.2.2 Direction of illumination ........................................................................................................................................... 8

4.2.3 Spectrum of illumination .......................................................................................................................................... 8

4.2.4 Stability of the light source ..................................................................................................................................... 8

4.2.5 Special types of illumination ................................................................................................................................. 9

4.3 Particle motion ........................................................................................................................................................................................ 9

4.4 Particle positioning ............................................................................................................................................................................. 9

4.5 Optical system ......................................................................................................................................................................................11

4.5.1 General...................................................................................................................................................................................11

4.5.2 Lens design ........................................................................................................................................................................11

4.5.3 Optical magnification ................................................................................................................................................11

4.5.4 Optical resolution .........................................................................................................................................................11

4.5.5 Lens errors .........................................................................................................................................................................11

4.6 Image capture device ......................................................................................................................................................................11

4.6.1 Matrix camera .................................................................................................................................................................11

4.6.2 Line scan camera ..........................................................................................................................................................11

4.6.3 Exposure time .................................................................................................................................................................12

4.6.4 Frame rate/line rate ........................................................................................................................................... ........12

4.6.5 Sensor resolution .........................................................................................................................................................12

4.7 Image analysis methods ...............................................................................................................................................................12

4.7.1 Image analysis process ............................................................................................................................................12

4.7.2 Robustness of the image analysis method ..............................................................................................13

4.7.3 Image correction ...........................................................................................................................................................13

4.7.4 Segmentation methods ........................................................................................................................................... .13

4.7.5 Particle classification ................................................................................................................................................14

4.8 Conversion to meaningful particle descriptors .......................................................................................................14

4.9 Statistical representation of descriptors .......................................................................................................................14

4.10 Particle dispersion technique .................................................................................................................................................14

4.11 Systematic corrections dealing with set-up characteristics .........................................................................14

5 Operational procedures .............................................................................................................................................................................15

5.1 General ........................................................................................................................................................................................................15

5.2 Instrument set-up and calibration ......................................................................................................................................15

5.2.1 Preliminaries ....................................................................................................................................................................15

5.2.2 Site of installation ........................................................................................................................................................15

5.2.3 Magnification and sensor resolution ...........................................................................................................15

5.2.4 Illumination .......................................................................................................................................................................16

5.2.5 Segmentation ...................................................................................................................................................................17

5.2.6 Contamination ................................................................................................................................................................17

5.3 Dispersing systems ...........................................................................................................................................................................18

5.3.1 Preliminary considerations .................................................................................................................................18

5.3.2 Particle velocity..............................................................................................................................................................18

5.3.3 Frame coverage ..............................................................................................................................................................19

© ISO 2021 – All rights reserved iii
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ISO/FDIS 13322-2:2021(E)

5.3.4 Medium .................................................................................................................................................................................19

5.3.5 Homogeneous dispersion and segregation ............................................................................................19

5.4 Operational qualification ............................................................................................................................................................19

5.5 Image enhancement algorithms ...........................................................................................................................................20

5.6 Measurements ......................................................................................................................................................................................20

5.6.1 Particle size and shape ............................................................................................................................................20

5.6.2 Pixel to length conversion .....................................................................................................................................20

5.6.3 Size class limits ...............................................................................................................................................................20

6 Sample preparation ........................................................................................................................................................................................21

6.1 Sample splitting and reduction ..............................................................................................................................................21

6.2 Touching particles .............................................................................................................................................................................21

6.3 Number of particles to be counted .....................................................................................................................................21

7 Accuracy and instrument qualification .....................................................................................................................................21

7.1 General ........................................................................................................................................................................................................21

7.2 Trueness ....................................................................................................................................................................................................22

7.2.1 General...................................................................................................................................................................................22

7.2.2 Qualification test ...........................................................................................................................................................22

7.2.3 Qualification acceptance ........................................................................................................................................22

7.3 Repeatability ..........................................................................................................................................................................................23

7.3.1 General...................................................................................................................................................................................23

7.3.2 Repeatability test ..........................................................................................................................................................23

7.4 Intermediate precision ..................................................................................................................................................................24

7.4.1 General...................................................................................................................................................................................24

7.4.2 Qualification acceptance ........................................................................................................................................24

8 Test report ................................................................................................................................................................................................................24

8.1 General ........................................................................................................................................................................................................24

8.2 Sample .........................................................................................................................................................................................................25

8.3 Dispersion ................................................................................................................................................................................................25

8.4 Image analysis instrument.........................................................................................................................................................25

8.5 Analyst identification .....................................................................................................................................................................26

Annex A (informative) Theoretical background ....................................................................................................................................27

Annex B (informative) Comparison between particle size distributions by number and by

volume ..........................................................................................................................................................................................................................30

Annex C (informative) Recommended particle velocity and exposure time ............................................................31

Annex D (informative) Particle diameter dependence on threshold selection ....................................................35

Annex E (normative) Requirements for reference material .....................................................................................................39

Annex F (informative) Robustness and ruggedness of the image analysis method .........................................42

Annex G (informative) Optional methods ....................................................................................................................................................45

Annex H (informative) Typical examples of sample feed and image capture systems ..................................46

Bibliography .............................................................................................................................................................................................................................54

iv © ISO 2021 – All rights reserved
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ISO/FDIS 13322-2:2021(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/ patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation on the meaning of ISO specific terms and expressions related to conformity

assessment, as well as information about ISO's adherence to the World Trade Organization (WTO)

principles in the Technical Barriers to Trade (TBT) see the following URL: www .iso .org/ iso/ foreword

.html.

This document was prepared by Technical Committee ISO/TC 24, Particle characterization including

sieving, Subcommittee SC 4, Particle characterization.

This second edition cancels and replaces the first edition (ISO 13322-2:2006), which has been

technically revised.
The main changes compared to the previous edition are as follows:
— the text has been aligned with changes introduced in ISO 13322-1:2014;

— clauses on instrumentation (principle) and operational procedures have been significantly

expanded;

— a new clause on accuracy and instrument qualification using particulate reference materials has

been added.
A list of all parts in the ISO 13322 series can be found on the ISO website.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.
© ISO 2021 – All rights reserved v
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ISO/FDIS 13322-2:2021(E)
Introduction

The ISO 13322 series is applicable to the analysis of images for the purpose of determining particle

size distributions. The purpose of this document is to provide guidance for measuring and describing

particle size distribution, using image analysis methods where particles are in motion. This entails

using techniques for dispersing particles in liquid or gas, taking in-focus, still images of them while

the particles are moving and subsequently analysing the images. This methodology is called dynamic

image analysis.

There are several image capture methods. Some typical methods are described in this document.

ISO 13322-1 on static image analysis methods assumes that an adequate image has already been

captured and concentrates upon the analysis of these images.
vi © ISO 2021 – All rights reserved
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FINAL DRAFT INTERNATIONAL STANDARD ISO/FDIS 13322-2:2021(E)
Particle size analysis — Image analysis methods —
Part 2:
Dynamic image analysis methods
1 Scope

This document describes a method to transfer the images from particles having relative motion to

binary images within practical systems, in which the particles in the images are individually separated.

Images of moving particles are created by an optical image capture device. Effects of particle movement

on the images are either minimized by the instrumentation or corrected by software procedures. This

method is applicable to the particle images that are clearly distinguishable from a static background.

Further processing of the binary image, which is then considered as static, is described in ISO 13322-1.

A dynamic image analysis system is capable of measuring higher number of particles compared to static

image analysis systems. This document provides guidance on instruments qualification for particle

size distribution measurements by using particulate reference materials. This document addresses

the relative movement of the particles with respect to each other, the effect of particle movement on

the image (motion blur), the movement and position along the optical axis (depth of field), and the

orientation of the particles with respect to the camera.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements 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.

ISO 9276-1, Representation of results of particle size analysis — Part 1: Graphical representation

ISO 9276-2, Representation of results of particle size analysis — Part 2: Calculation of average particle

sizes/diameters and moments from particle size distributions

ISO 9276-6, Representation of results of particle size analysis — Part 6: Descriptive and quantitative

representation of particle shape and morphology

ISO 13322-1, Particle size analysis — Image analysis methods — Part 1: Static image analysis methods

ISO 14488, Particulate materials — Sampling and sample splitting for the determination of particulate

properties

ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories

3 Terms, definitions and symbols
3.1 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 13322-1 and the following

apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
© ISO 2021 – All rights reserved 1
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ISO/FDIS 13322-2:2021(E)
3.1.1
acceptable depth of field

depth with respect to focal depth where the sharpness of the edges of the

particle images is accepted for segmentation

Note 1 to entry: The acceptable depth of field is decided by the software on the basis of sharpness of the images

and is also dependent on the particle size.
3.1.2
accuracy

closeness of agreement between a test result or measurement result and the true value (3.1.20)

Note 1 to entry: In practice, the accepted reference value is substituted for the true value.

Note 2 to entry: The term “accuracy”, when applied to a set of test or measurement results, involves a combination

of random components and a common systematic error or bias component.

Note 3 to entry: Accuracy refers to a combination of trueness (3.1.19) and precision (3.1.12).

[SOURCE: ISO 3534-2:2006, 3.3.1]
3.1.3
certified reference material
CRM

reference material (3.1.13) characterised by a metrologically valid procedure for one or more specified

properties, accompanied by an RM certificate that provides the value of the specified property, its

associated uncertainty, and a statement of metrological traceability

Note 1 to entry: The concept of value includes a nominal property or a qualitative attribute such as identity or

sequence. Uncertainties for such attributes may be expressed as probabilities or levels of confidence.

Note 2 to entry: Metrologically valid procedures for the production and certification of RMs are given in, among

others, ISO 17034 and ISO Guide 35.
Note 3 to entry: ISO Guide 31 gives guidance on the contents of RM certificates.
Note 4 to entry: ISO/IEC Guide 99:2007 has an analogous definition.
[SOURCE: ISO Guide 35:2017, 3.2]
3.1.4
flow cell
measurement cell inside which the gas- or liquid-particle mixture flows
3.1.5
frame coverage

fraction of the image area that is obscured by the projection area of all

segmented particles counted in the image

Note 1 to entry: Frame coverage can be expressed as a part or percentage of image area.

3.1.6
intermediate precision

accuracy (3.1.2) and precision under intermediate precision conditions (3.1.7)

[SOURCE: ISO 3534-2:2006, 3.3.15, modified — "and precision" and the field of application < dynamic

image analysis > have been added.]
2 © ISO 2021 – All rights reserved
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ISO/FDIS 13322-2:2021(E)
3.1.7
intermediate precision conditions

conditions where test results or measurement results are obtained on

different dynamic image analysis instruments and with different operators using the same prescribed

method

Note 1 to entry: There are four elements to the operating condition: time, calibration, operator and equipment.

3.1.8
image capture device

matrix camera or line scan camera for converting an optical image to digital image data

3.1.9
measurement zone

volume in which particles are measured by an image analyser, formed by the measurement frame

including a third dimension from the acceptable depth of field (3.1.1)
Note 1 to entry: The measurement zone is defined by the software (see 3.1.1).
3.1.10
orifice tube

tube with an aperture through which a stream of fluid with dispersed particles flows

3.1.11
illumination

continuous illumination for an image capture device (3.1.8) with an electronic exposure time controller,

or illumination of short duration for a synchronized image capture device
3.1.12
precision

closeness of agreement between independent test/measurement results obtained under stipulated

conditions

Note 1 to entry: Precision depends only on the distribution of random errors and does not relate to the true value

(3.1.20) or the specified value.

Note 2 to entry: The measure of precision is usually expressed in terms of imprecision and computed as a

standard deviation of the test results or measurement results. Less precision is reflected by a larger standard

deviation.

Note 3 to entry: Quantitative measures of precision depend critically on the stipulated conditions. Repeatability

conditions (3.1.15) and reproducibility conditions are particular sets of extreme stipulated conditions.

[SOURCE: ISO 3534-2:2006, 3.3.4]
3.1.13
reference material
material, sufficiently homoge
...

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