Fine ceramics (advanced ceramics, advanced technical ceramics) -- Measurement method of spectral reflectance of fine ceramic thin films under humid conditions

This document specifies the procedure for measuring the spectral reflectance of fine ceramic thin films in an environment with variable relative humidity by using a general-purpose spectrophotometer.

Céramiques techniques -- Méthode de mesurage de la transmittance spectrale des films minces de céramiques fines en conditions humides

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Status
Published
Publication Date
28-Apr-2021
Technical Committee
Drafting Committee
Current Stage
5060 - Close of voting Proof returned by Secretariat
Start Date
24-Mar-2021
Completion Date
24-Mar-2021
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INTERNATIONAL ISO
STANDARD 23738
First edition
2021-04
Fine ceramics (advanced ceramics,
advanced technical ceramics) —
Measurement method of spectral
reflectance of fine ceramic thin films
under humid conditions
Céramiques techniques — Méthode de mesurage de la transmittance
spectrale des films minces de céramiques fines en conditions humides
Reference number
ISO 23738:2021(E)
ISO 2021
---------------------- Page: 1 ----------------------
ISO 23738:2021(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 23738:2021(E)
Contents Page

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

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

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

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

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

4 Principle ........................................................................................................................................................................................................................ 2

5 Measurement room ambient environment .............................................................................................................................. 2

6 Test pieces ................................................................................................................................................................................................................... 2

7 Measuring apparatus ....................................................................................................................................................................................... 3

7.1 Apparatus configuration ................................................................................................................................................................. 3

7.2 Spectrophotometer calibration ................................................................................................................................................ 4

8 Environmental conditions and control procedures ......................................................................................................... 5

9 Reflectance measurement procedure ............................................................................................................................................ 5

10 Evaluations of spectral shifts between dry and humid conditions ..................................................................5

10.1 General ........................................................................................................................................................................................................... 5

10.2 Single-layer films ................................................................................................................................................................................... 6

10.3 Anti-reflective coatings .................................................................................................................................................................... 6

10.4 Edge filters .................................................................................................................................................................................................. 8

11 Test report ................................................................................................................................................................................................................10

Annex A (informative) Structure and function of environmental mini-chamber ...............................................12

© ISO 2021 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO 23738:2021(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 206, Fine ceramics.

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 23738:2021(E)
Introduction

Fine ceramic thin films are used in many optical applications, such as anti-reflective coatings, infrared

sensor cut filters, X-ray sensor cut filters and band-pass filters. Even though the spectral reflectance

of fine ceramic thin films is specified for each product, the refractive index and the optical properties

change if these thin films are exposed to a humid environment. The reason for such changes in the

optical properties is that water is adsorbed onto the surfaces inside the voids of fine ceramic thin films.

A standard for evaluating the reliability of these films under a range of humidity conditions is therefore

necessary. A standard for determining the spectral transmittance under humid and dry conditions

was developed in ISO 17861. This document provides test methods that enable changes in the spectral

reflectance of fine ceramic coatings in a humid environment due to water adsorption to be evaluated

easily and accurately. The aim of this document is to promote the rapid adoption of this test method to

facilitate further growth in this industry.
© ISO 2021 – All rights reserved v
---------------------- Page: 5 ----------------------
INTERNATIONAL STANDARD ISO 23738:2021(E)
Fine ceramics (advanced ceramics, advanced technical
ceramics) — Measurement method of spectral reflectance
of fine ceramic thin films under humid conditions
1 Scope

This document specifies the procedure for measuring the spectral reflectance of fine ceramic thin films

in an environment with variable relative humidity by using a general-purpose spectrophotometer.

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 8980-3, Ophthalmic optics — Uncut finished spectacle lenses — Part 3: Transmittance specifications

and test methods
ISO 9211, Optics and photonics — Optical coatings

ISO 17861, Fine ceramics (advanced ceramics, advanced technical ceramics) — Measurement method of

spectral transmittance of fine ceramics thin films under humid condition
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 8980-3, ISO 9211 and

ISO 17861 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 http:// www .electropedia .org/
3.1
half of maximum/minimum reflectance wavelength
R1/2

wavelength at which the reflectance is equal to half of the maximum and minimum values observed in a

spectral reflectance curve obtained for a certain range of wavelength
3.2
environmental mini-chamber
small chamber that is used to control humidity

Note 1 to entry: This chamber is equipped with a quartz window for the optical beam inlet and outlet, an

evacuation feedthrough to evacuate the mini-chamber and an inlet to feed air with a controlled humidity to the

mini-chamber.
3.3
spectral reflectance

regularly reflected or spectral component of the illumination (i.e. light that is reflected in a mirror-like

way off a surface at the same angle and in the same plane as the incident ray) that is measured by using

a spectral reflectometer
© ISO 2021 – All rights reserved 1
---------------------- Page: 6 ----------------------
ISO 23738:2021(E)
3.4
monochromator

optical device that transmits a specific range of wavelengths from a polychromatic light

3.5
spectrophotometer
optical instrument that measures spectral transmittance or reflectance

Note 1 to entry: This instrument consists of an optical source, a monochromator, a sample chamber, an optical

detector, a signal processor, a data processor, and an interface
3.6
double-beam spectrophotometer

type of spectrophotometer that is utilized to compare the light intensity of a reference sample with that

of a test piece

Note 1 to entry: Compared with a single-beam spectrophotometer, this instrument provides a higher level of

measurement stability. In a double-beam spectrophotometer, the energy of the source light beam is divided into

two beams: a reference beam and a sample beam. The energy of the sample beam is detected by referring to the

energy of the reference beam.
3.7
integrating sphere

optical component consisting of a hollow spherical cavity with an inner surface that is covered with a

diffuse white reflective coating

Note 1 to entry: The cavity is equipped with small holes for the mounting of a test piece and for the inlet and

outlet of the light beam.
4 Principle

Fine ceramic thin films sometimes possess a voided micro columnar structure. Due to this structure,

moisture in the air is adsorbed onto the surfaces of columns with voids between them. The quantity of

adsorbed water is affected by the hydrostatic vapour pressure and temperature in the environment.

Depending on the quantity of water that is adsorbed, the refractive index of a thin film changes,

resulting in a change in its spectral reflectance. To evaluate what effects the adsorption of water on the

surface of voids in fine ceramic thin films has on the spectral reflectance of thin films, it is necessary

to measure the optical properties under a vacuum, a high-humidity environment and a low-hu

...

INTERNATIONAL ISO
STANDARD 23738
First edition
Fine ceramics (advanced ceramics,
advanced technical ceramics) —
Measurement method of spectral
reflectance of fine ceramic thin films
under humid conditions
PROOF/ÉPREUVE
Reference number
ISO 23738:2021(E)
ISO 2021
---------------------- Page: 1 ----------------------
ISO 23738:2021(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 PROOF/ÉPREUVE © ISO 2021 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 23738:2021(E)
Contents Page

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

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

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

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

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

4 Principle ........................................................................................................................................................................................................................ 2

5 Measurement room ambient environment .............................................................................................................................. 2

6 Test pieces ................................................................................................................................................................................................................... 2

7 Measuring apparatus ....................................................................................................................................................................................... 3

7.1 Apparatus configuration ................................................................................................................................................................. 3

7.2 Spectrophotometer calibration ................................................................................................................................................ 4

8 Environmental conditions and control procedures ......................................................................................................... 5

9 Reflectance measurement procedure ............................................................................................................................................ 5

10 Evaluations of spectral shifts between dry and humid conditions ..................................................................5

10.1 General ........................................................................................................................................................................................................... 5

10.2 Single-layer films ................................................................................................................................................................................... 6

10.3 Anti-reflective coatings .................................................................................................................................................................... 6

10.4 Edge filters .................................................................................................................................................................................................. 8

11 Test report ................................................................................................................................................................................................................10

Annex A (informative) Structure and function of environmental mini-chamber ...............................................12

© ISO 2021 – All rights reserved PROOF/ÉPREUVE iii
---------------------- Page: 3 ----------------------
ISO 23738:2021(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 206, Fine ceramics.

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 2021 – All rights reserved
---------------------- Page: 4 ----------------------
ISO 23738:2021(E)
Introduction

Fine ceramic thin films are used in many optical applications, such as anti-reflective coatings, infrared

sensor cut filters, X-ray sensor cut filters and band-pass filters. Even though the spectral reflectance

of fine ceramic thin films is specified for each product, the refractive index and the optical properties

change if these thin films are exposed to a humid environment. The reason for such changes in the

optical properties is that water is adsorbed onto the surfaces inside the voids of fine ceramic thin films.

A standard for evaluating the reliability of these films under a range of humidity conditions is therefore

necessary. A standard for determining the spectral transmittance under humid and dry conditions

was developed in ISO 17861. This document provides test methods that enable changes in the spectral

reflectance of fine ceramic coatings in a humid environment due to water adsorption to be evaluated

easily and accurately. The aim of this document is to promote the rapid adoption of this test method to

facilitate further growth in this industry.
© ISO 2021 – All rights reserved PROOF/ÉPREUVE v
---------------------- Page: 5 ----------------------
INTERNATIONAL STANDARD ISO 23738:2021(E)
Fine ceramics (advanced ceramics, advanced technical
ceramics) — Measurement method of spectral reflectance
of fine ceramic thin films under humid conditions
1 Scope

This document specifies the procedure for measuring the spectral reflectance of fine ceramic thin films

in an environment with variable relative humidity by using a general-purpose spectrophotometer.

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 8980-3, Ophthalmic optics — Uncut finished spectacle lenses — Part 3: Transmittance specifications

and test methods
ISO 9211, Optics and photonics — Optical coatings

ISO 17861, Fine ceramics (advanced ceramics, advanced technical ceramics) — Measurement method of

spectral transmittance of fine ceramics thin films under humid condition
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 8980-3, ISO 9211 and

ISO 17861 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 http:// www .electropedia .org/
3.1
half of maximum/minimum reflectance wavelength
R1/2

wavelength at which the reflectance is equal to half of the maximum and minimum values observed in a

spectral reflectance curve obtained for a certain range of wavelength
3.2
environmental mini-chamber
small chamber that is used to control humidity

Note 1 to entry: This chamber is equipped with a quartz window for the optical beam inlet and outlet, an

evacuation feedthrough to evacuate the mini-chamber and an inlet to feed air with a controlled humidity to the

mini-chamber.
3.3
spectral reflectance

regularly reflected or spectral component of the illumination (i.e. light that is reflected in a mirror-like

way off a surface at the same angle and in the same plane as the incident ray) that is measured by using

a spectral reflectometer
© ISO 2021 – All rights reserved PROOF/ÉPREUVE 1
---------------------- Page: 6 ----------------------
ISO 23738:2021(E)
3.4
monochromator

optical device that transmits a specific range of wavelengths from a polychromatic light

3.5
spectrophotometer
optical instrument that measures spectral transmittance or reflectance

Note 1 to entry: This instrument consists of an optical source, a monochromator, a sample chamber, an optical

detector, a signal processor, a data processor, and an interface
3.6
double-beam spectrophotometer

type of spectrophotometer that is utilized to compare the light intensity of a reference sample with that

of a test piece

Note 1 to entry: Compared with a single-beam spectrophotometer, this instrument provides a higher level of

measurement stability. In a double-beam spectrophotometer, the energy of the source light beam is divided into

two beams: a reference beam and a sample beam. The energy of the sample beam is detected by referring to the

energy of the reference beam.
3.7
integrating sphere

optical component consisting of a hollow spherical cavity with an inner surface that is covered with a

diffuse white reflective coating

Note 1 to entry: The cavity is equipped with small holes for the mounting of a test piece and for the inlet and

outlet of the light beam.
4 Principle

Fine ceramic thin films sometimes possess a voided micro columnar structure. Due to this structure,

moisture in the air is adsorbed onto the surfaces of columns with voids between them. The quantity of

adsorbed water is affected by the hydrostatic vapour pressure and temperature in the environment.

Depending on the quantity of water that is adsorbed, the refractive index of a thin film changes,

resulting in a change in its spectral reflectance. To evaluate what effects the adsorption of water on the

surface of voids in fine ceramic thin films has on the spectral reflectance of thin films, it is necessary

to measure the optical properties under a vacuum, a high-humidity environment and a low-humidity

environment. Comparing the results measured under a vacuum, a high-humidity environment and a

low-humidity environmen
...

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