ISO 19741:2018

INTERNATIONAL ISO
STANDARD 19741
First edition
2018-05
Optics and photonics — Optical
materials and components — Test
method for striae in infrared optical
materials
Optique et photonique — Matériaux et composants optiques —
Méthodes d’essai pour déterminer les stries des matériaux optiques
infrarouges
Reference number
©
ISO 2018
© ISO 2018
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ii © ISO 2018 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Apparatus . 2
6 Test conditions . 3
6.1 Environmental temperature . 3
6.2 Relative air humidity . 3
7 Sample . 3
8 Procedure. 4
8.1 Projection measurement . 4
8.2 Schlieren measurement . 4
9 Data processing . 5
10 Test report . 5
Annex A (informative) Test record for striae in infrared optical materials .6
Bibliography . 7
Foreword
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This document was prepared by Technical Committee ISO/TC 172, Optics and photonics, Subcommittee
SC3, Optical materials and components.
iv © ISO 2018 – All rights reserved

INTERNATIONAL STANDARD ISO 19741:2018(E)
Optics and photonics — Optical materials and components
— Test method for striae in infrared optical materials
1 Scope
This document specifies the principle, apparatus, condition, sample, procedure and data processing of
measuring striae in infrared optical materials.
It is applicable to the determination of striae in infrared optical materials, such as infrared optical glass,
which is opaque to visible wavelengths and whose transmission optical spectra are beyond 0,78 µm.
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 10110-7, Optics and photonics — Preparation of drawings for optical elements and systems — Part 7:
Surface imperfections
ISO 10110-8, Optics and photonics — Preparation of drawings for optical elements and systems — Part 8:
Surface texture; roughness and waviness
3 Terms and definitions
For the purposes of this document, the following terms and definitions 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
striae
regions of resembling bands, layers or rods formed due to short range severe deviations of refractive
index in infrared optical materials, observed only by infrared detecting devices
3.2
striae value
average grey level of striae (3.1) multiplying the percentage of striae area per thickness of infrared
optical materials
4 Principle
The principle of this test is to illuminate a sample with collimated infrared radiation and image the
material in a Schlieren or projection imaging system. The striae will be imaged and measured, and then
the area and the product of striae area percentage to the mean grey level will be calculated. When the
projection optical system is adjusted to a beam-contracting telescope system, it is known as a projection
measurement system. And when the projection optical system is adjusted to a camera system which
utilizes a knife edge device, it is known as a Schlieren measurement system. The schematic diagram of
striae measurement in infrared optical materials is shown in Figure 1.
Key
1 light source 8 lens 2 of projection optical system
2 condenser 9 image sensor
3 light source diaphragm 10 computer image collecting, processing and
displaying system
4 i
...