ISO 9211-1:2024

International
Standard
ISO 9211-1
Fourth edition
Optics and photonics — Optical
2024-02
coatings —
Part 1:
Vocabulary
Optique et photonique — Traitements optiques —
Partie 1: Vocabulaire
Reference number
© ISO 2024
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
3.1 Basic terms and definitions .1
3.1.1 General terms .1
3.1.2 Terms for optical properties of a coated surface .2
3.1.3 Terms for polarization .4
3.1.4 Phase related terms .5
3.2 Designations of coatings by principal function .6
3.2.1 Reflecting function .6
3.2.2 Antireflecting function .6
3.2.3 Beam splitting function.6
3.2.4 Attenuating function.7
3.2.5 Bandpass or band rejection filtering function .7
3.2.6 Selecting or combining function .7
3.2.7 Polarizing function .7
3.2.8 Phase changing function .7
3.2.9 Absorbing function .8
3.2.10 Supplementary function .8
3.3 Terms related to common coating imperfections .9
3.3.1 Point-like imperfections .9
3.3.2 Line-like imperfections .9
3.3.3 Area-like imperfections .10
3.3.4 Volume-like imperfections .10
Annex A (informative) Micrographs of common types of coating imperfections .11
Bibliography .20

iii
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,
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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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
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This document was prepared by Technical Committee ISO/TC 172, Optics and photonic, Subcommittee SC 3,
Optical materials and components.
This fourth edition cancels and replaces the third edition (ISO 9211-1:2018), which has been technically
revised.
The main changes are as follows:
— addition of the definition of spectral optical density;
— explanations of subscript for spectral average;
— explanations of average transmittance, reflectance, absorptance and optical density over wavelength or
wave number.
A list of all parts in the ISO 9211 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
Introduction
The optical properties of a coated surface are characterized by spectrophotometric values. These values
relate to the energy transported by electromagnetic waves (radiant or luminous) and they vary as a function
of the wavelength, the angle of incidence, and the state of polarization. Additional influences can be caused
by scattering.
NOTE 1 The functional spectral dependency is generally indicated by including the wavelength (λ) in parentheses
as part of the symbol.
NOTE 2 The wavelength (λ) can be replaced by the wavenumber (σ) or the photon energy (hν). h = Planck constant;
ν = frequency. The units recommended are the nanometre (nm) or the micrometre (µm) for the wavelength, the
−1
reciprocal centimetre (cm ) for the wavenumber and the electron volt (eV) for the photon energy.
When a coating is used at an angle of incidence different from zero, its characteristics depend upon the state
of polarization of the incident radiation and it can influence the polarization state of the emergent radiation.
It might then be necessary to indicate the orientation of the electric field vector in relation to the plane of
incidence.
The coatings are defined according to their function, i.e. according to the nature of the principal modification
to the surface properties that they realize. A coating intended to realize a principal function as defined in
Table 1 can also include one or more secondary functions. Their relative importance with regard to the
principal function may be indicated.
A surface for visual applications can be characterized by colorimetric parameters. These depend on the
reference illumination source, the reference observer, and the optical properties of the surface. Colorimetric
parameters are not part of this standard.
Examples of coating imperfections are given in Annex A. Test methods for the surface imperfections are
described in ISO 14997.
v
International Standard ISO 9211-1:2024(en)
Optics and photonics — Optical coatings —
Part 1:
Vocabulary
WARNING — The electronic file of this document contains colours which are considered to be
useful for the correct understanding of the document. Users should therefore consider printing this
document using a colour printer.
1 Scope
This document defines terms relevant to optical coatings. These terms are grouped in four classes: Terms
and definitions, definition of coatings by function, definitions of common coating imperfections and other
definitions.
This document identifies surface treatments of components and substrates excluding ophthalmic optics
(spectacles) by the application of optical coatings and gives a standard form for their specification. It defines
the general characteristics and the test and measurement methods whenever necessary, but is not intended
to define the process method.
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 11145, Optics and photonics — Lasers and laser-related equipment — Vocabulary and symbols
ISO 80000-7, Quantities and units — Part 7: Light and radiation
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 11145 and ISO 80000-7 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/
3.1 Basic terms and definitions
3.1.1 General terms
3.1.1.1
surface treatment of components and substrates
application of a coating of material(s) intended to modify the optical, physical or chemical characteristics
originally possessed by the surface of a component
Note 1 to entry: The substrates are considered to be geometrically perfect and optically homogeneous. In reality, an
assembly made up of a substrate and a coating is identified and measured experimentally as an entity.

3.1.1.2
incident medium
medium from which the electromagnetic radiation enters a coating
3.1.1.3
emergent medium
medium into which the electromagnetic radiation exits a coating
Note 1 to entry: Besides acting as mechanical support, the substrate carrying the coating physically can constitute the
incident medium and/or the emergent medium.
3.1.1.4
clear aperture
effective aperture
surface area to meet specifications
3.1.1.5
rim
surface area outside of the clear aperture
3.1.1.6
witness sample
sample that represents the actual coated component used for spectral and environmental testing
Note 1 to entry: The details of witness samples and measurements (e.g. material, surface texture, dimensions, number
per batch, position in the coating chamber, etc.) is subject to agreement between manufacturer and customer.
3.1.2 Terms for optical properties of a coated surface
3.1.2.1
spectral transmittance
τ(λ)
ratio of the spe
...