BS ISO 19742:2018 pdf download

BS ISO 19742:2018 pdf download.Optics and photonics — Optical materials and components — Test method for bubbles and inclusions in infrared optical materials
1 Scope
This document specifies the apparatus, condition, sample, procedure and data processing of measuring bubbles and inclusions in infrared optical materials.
It is applicable to the determination of bubbles and inclusions in infrared optical materials, such as infrared optical glass, infrared crystals and infrared ceramics, which are 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 10110-8, 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 bubble
gaseous voids in the bulk infrared glass and ceramics materials, of generally circular cross section
3.2 inclusion
all localized bulk infrared material defects of generally circular cross section
EXAMPLE Small knots, small stones, sand and crystals.
3.3 material imperfection value
total sum of the cross-sectional area of bubbles (3.1) and inclusions (3.2) per 100 cm 3 of a sample
4 Principle
The principle of this test is to measure bubbles and inclusions by utilizing a diffuse infrared light source to illuminate the test sample, calculate their number and sum up their cross-sectional areas per unit volume. A schematic diagram of the measurement of bubbles and inclusions is shown in Figure 1.
5.2 Infrared light source system
The infrared light source system consists of an infrared light source and a diffuser screen. The infrared light source emnits light which covers the transmission spectra region of samples. The intensity and uniformity of the infrared light source shall meet the requirements of the response of the image sensor. The diffuser screen shall be uniform and meet the requirements of measurements.
5.3 Infrared imaging system
The infrared imaging system consists of an imaging lens and an image sensor. The depth focus of the imaging lens should cover the thickness of samples. The object spatial resolution of the imaging lens corresponding to the image sensor shall be less than the specified minimum size of bubbles and inclusions in samples. The value of the object spatial resolution is recommended to be not more than 0,1 mm. An array image sensor is generally used. The working wavelength band of an infrared image sensor should be within the transmission spectrum of the sample measurement. When the scanning interfaces between sections can be clearly identified and the images of bubbles and inclusions do not overlap, a scanning image system may be used.