Optics and photonics -- Test methods for telescopic systems

This document specifies the test method for the measurement of the axial colour performance which includes axial chromatic aberration and spherical aberration of telescopic systems and observational telescopic instruments.

Optique et photonique -- Méthodes d'essai pour systèmes télescopiques

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Status
Published
Publication Date
09-Feb-2021
Current Stage
5060 - Close of voting Proof returned by Secretariat
Start Date
30-Dec-2020
Completion Date
30-Dec-2020
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INTERNATIONAL ISO
STANDARD 14490-10
First edition
2021-02
Optics and photonics — Test methods
for telescopic systems —
Part 10:
Test methods for axial colour
performance
Optique et photonique — Méthodes d'essai pour systèmes
télescopiques —
Partie 10: Méthodes d'essai pour la performance de couleur axiale
Reference number
ISO 14490-10:2021(E)
ISO 2021
---------------------- Page: 1 ----------------------
ISO 14490-10:2021(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

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2021 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 14490-10:2021(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

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

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

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Requirements .......................................................................................................................................................................................................... 1

4.1 General ........................................................................................................................................................................................................... 1

4.2 Test arrangement .................................................................................................................................................................................. 1

4.3 Preparation and carrying out of measurements ........................................................................................................ 2

4.4 Determination of results ................................................................................................................................................................. 2

4.5 Uncertainty and fundamental limit of the measurement ................................................................................... 3

4.6 Test report ................................................................................................................................................................................................... 3

Annex A (informative) Measurement method for axial colour performance of the dioptric tester ...4

Bibliography ................................................................................................................................................................................................................................ 6

© ISO 2021 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO 14490-10:2021(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 of the voluntary nature of standards, 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 www .iso .org/

iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 172, Optics and photonics, Subcommittee

SC 4, Telescopic systems.
A list of all parts in the ISO 14490 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.
iv © ISO 2021 – All rights reserved
---------------------- Page: 4 ----------------------
ISO 14490-10:2021(E)
Introduction

ISO 14490-7 mentions several characteristics to determine image quality of telescopic systems besides

the limit of resolution evaluation. One unmentioned characteristic in ISO 14490-7 is the “axial colour

performance” which may be noted by the user as a coloured halo around objects or even a hue of

objects in the centre of the field of view. Typically, the axial colour performance also affects the colour

performance in the entire field of view.

The axial colour performance of a telescopic system is mainly determined by two major intrinsic

contributions. These are spherical aberration and axial chromatic aberration. According to ISO 10934

axial chromatic aberration is defined as the aberration of a lens, by which light of different wavelengths

is focused at different points along the optical axis. The axial chromatic aberration originates from the

intrinsic difference of the refractive index of glass as a function of the incident wavelength of light,

i.e. the dispersion. For a singlet (positive) lens the axial chromatic aberration yields different focal

lengths for different wavelengths, which may also be called chromatic focal shift. Multi-lens groups or

assemblies are designed to reduce and compensate this focal shift to go below the intrinsic dispersion

of singlet systems. The footprint of the axial chromatic correction of lenses is partially classified by

terms like “achromatic” or “apochromatic” lenses.

Axial chromatic aberration originates from the dispersion of the lens material. In contrast, spherical

aberration is related to the geometry of a lens and is classified as a monochromatic aberration. Spherical

aberration causes rays in the image space to intersect the optical axis before or after the image point

formed by the paraxial rays (see also ISO 10934). As a consequence the “best focus” is not well defined

even for a monochromatic evaluation of a system. From that it is obvious that the measurement of a

pure axial chromatic aberration may be influenced by spherical aberration.

This document thus describes the measurement of the joint effect of these two major contributions

since in practical use an observer will not be able to separate these two effects. However, for deeper

analysis in the laboratory the two effects may be analysed separately.

In the case of afocal systems, such as telescopes, the axial chromatic aberration as well as the spherical

aberration of the objective lens is imaged to infinity by the eyepiece (looked at by the user) and can be

measured in dioptres. The measurement of the axial colour performance as described in this document

may be combined with a monochromatic evaluation of the modulation transfer function (MTF, see

ISO 9336-3) to obtain an overall figure for the imaging performance of a telescopic system.

© ISO 2021 – All rights reserved v
---------------------- Page: 5 ----------------------
INTERNATIONAL STANDARD ISO 14490-10:2021(E)
Optics and photonics — Test methods for telescopic
systems —
Part 10:
Test methods for axial colour performance
1 Scope

This document specifies the test method for the measurement of the axial colour performance which

includes axial chromatic aberration and spherical ab
...

INTERNATIONAL ISO
STANDARD 14490-10
First edition
Optics and photonics — Test methods
for telescopic systems —
Part 10:
Test methods for axial colour
performance
Optique et photonique — Méthodes d'essai pour systèmes
télescopiques —
Partie 10: Méthodes d'essai pour la performance de couleur axiale
PROOF/ÉPREUVE
Reference number
ISO 14490-10:2020(E)
ISO 2020
---------------------- Page: 1 ----------------------
ISO 14490-10:2020(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2020

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

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii PROOF/ÉPREUVE © ISO 2020 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 14490-10:2020(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

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

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

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Requirements .......................................................................................................................................................................................................... 1

4.1 General ........................................................................................................................................................................................................... 1

4.2 Test arrangement .................................................................................................................................................................................. 1

4.3 Preparation and carrying out of measurements ........................................................................................................ 2

4.4 Determination of results ................................................................................................................................................................. 2

4.5 Uncertainty and fundamental limit of the measurement ................................................................................... 3

4.6 Test report ................................................................................................................................................................................................... 3

Annex A (informative) Measurement method for axial colour performance of the dioptric tester ...4

Bibliography ................................................................................................................................................................................................................................ 6

© ISO 2020 – All rights reserved PROOF/ÉPREUVE iii
---------------------- Page: 3 ----------------------
ISO 14490-10:2020(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 of the voluntary nature of standards, 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 www .iso .org/

iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 172, Optics and photonics, Subcommittee

SC 4, Telescopic systems.
A list of all parts in the ISO 14490 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.
iv PROOF/ÉPREUVE © ISO 2020 – All rights reserved
---------------------- Page: 4 ----------------------
ISO 14490-10:2020(E)
Introduction

ISO 14490-7 mentions several characteristics to determine image quality of telescopic systems besides

the limit of resolution evaluation. One unmentioned characteristic in ISO 14490-7 is the “axial colour

performance” which may be noted by the user as a coloured halo around objects or even a hue of

objects in the center of the field of view. Typically, the axial color performance also affects the colour

performance in the entire field of view.

The axial colour performance of a telescopic system is mainly determined by two major intrinsic

contributions. These are spherical aberration and axial chromatic aberration. According to ISO 10934

axial chromatic aberration is defined as the aberration of a lens, by which light of different wavelengths

is focused at different points along the optical axis. The axial chromatic aberration originates from the

intrinsic difference of the refractive index of glass as a function of the incident wavelength of light,

i.e. the dispersion. For a singlet (positive) lens the axial chromatic aberration yields different focal

lengths for different wavelengths, which may also be called chromatic focal shift. Multi-lens groups or

assemblies are designed to reduce and compensate this focal shift to go below the intrinsic dispersion

of singlet systems. The footprint of the axial chromatic correction of lenses is partially classified by

terms like “achromatic” or “apochromatic” lenses.

Axial chromatic aberration originates from the dispersion of the lens material. In contrast, spherical

aberration is related to the geometry of a lens and is classified as a monochromatic aberration. Spherical

aberration causes rays in the image space to intersect the optical axis before or after the image point

formed by the paraxial rays (see also ISO 10934). As a consequence the “best focus” is not well defined

even for a monochromatic evaluation of a system. From that it is obvious that the measurement of a

pure axial chromatic aberration may be influenced by spherical aberration.

This document thus describes the measurement of the joint effect of these two major contributions

since in practical use an observer will not be able to separate these two effects. However, for deeper

analysis in the laboratory the two effects may be analysed separately.

In the case of afocal systems, such as telescopes, the axial chromatic aberration as well as the spherical

aberration of the objective lens is imaged to infinity by the eyepiece (looked at by the user) and can be

measured in dioptres. The measurement of the axial colour performance as described in this document

may be combined with a monochromatic evaluation of the modulation transfer function (MTF, see

ISO 9336-3) to obtain an overall figure for the imaging performance of a telescopic system.

© ISO 2020 – All rights reserved PROOF/ÉPREUVE v
---------------------- Page: 5 ----------------------
INTERNATIONAL STANDARD ISO 14490-10:2020(E)
Optics and photonics — Test methods for telescopic
systems —
Part 10:
Test methods for axial colour performance
1 Scope

This document specifies the test method for the measurement of the axial colour performance which

includes axial chromatic aberration and spherical aberration of tele
...

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