GB/T 36403-2018 in English

《GB/T 36403-2018红外光学玻璃红外透过率测试方法 傅里叶变换法》由TC447（全国工业玻璃和特种玻璃标准化技术委员会）归口，主管部门为中国建筑材料联合会。

ChinaStandards.net is in charge of this English translation. In case of any doubt about the English translation, the Chinese original shall be considered authoritative.

This standard is developed in accordance with the rules given in GB/T 1.1-2009.

This standard was proposed by China Building Materials Federation.

This standard is under the jurisdiction of the National Technical Committee on Industrial Glass and Special Glass of Standardization Administration of China (SAC/TC 447).


Test methods of infrared transmittance for infrared optical glass - Fourier transform method

1 Scope

This standard specifies the terms and definitions, test principle, test equipment, test sample, test environment, test procedures, data processing, measurement uncertainty and test report of infrared transmittance for infrared optical glass by Fourier transform method.

This standard is applicable to the test of infrared transmittance for infrared optical glass with a wavelength of not less than 2.5μm. It may also serve as reference for infrared optical materials such as crystals and ceramics.

2 Terms and definitions

For the purposes of this document, the following terms and definitions apply.

2.1
infrared transmittance
transmittance of infrared optical glass in infrared band, which is characterized by the percentage of radiation (light) flux before and after transmission through the sample

3 Test principle

The test principle of infrared transmittance for infrared optical glass by Fourier transform method is shown in Figure 1.



Key:

1——infrared light source;

2——Michelson interferometer;

3——moving mirror;

4——beam splitter;

5——fixed mirror;

6——sample chamber;

7——infrared detector;

8——signal analog-to-digital converter;

9——computer processing system.

Figure 1 Schematic diagram for test of infrared transmittance by Fourier transform method

The infrared spectrum signal of the infrared light source after collimation and beam expansion is incident on the Michelson interferometer, and the emitted infrared spectrum is a modulated interference pattern optical signal I(x, v) with light intensity distributed periodically. The interference spectrum optical signal, after entering the sample chamber and being transmitted by the sample, is focused on the infrared detector, and the interference pattern optical signal I'(x, v) transmitted by the sample is collected, while the interference pattern optical signal directly emitted without being transmitted by the sample is still I(x, v). After passing through the signal analog-to-digital converter, the infrared transmittance of the sample under test changing with the light wave number (wavelength) is obtained through Fourier transform on computer, as shown in Equation (1).

(1)

where,

(v)——the transmittance distribution of the sample under test changing with the wave number;

I′(x, v)——the intensity distribution of interference light transmitted through the sample changing with the optical path difference, lm;

I(x, v)——the intensity distribution of interference light not transmitted through the sample changing with the optical path difference, lm;

x——the optical path difference, cm;

v——the wave number, i.e. the reciprocal of the wavelength, cm-1.

4 Test equipment

4.1 Configuration of apparatus

The infrared transmittance tester consists of infrared light source, Michelson interferometer (beam splitter, moving mirror and fixed mirror), sample chamber, infrared detector, signal analog-to-digital converter and computer processing system.

4.2 Requirements for apparatus

The emission wavelength range of infrared light source used for the apparatus shall generally cover 2.5~25μm, and the light source shall be subjected to collimation and uniform beam expansion before radiating in the interferometer. The effective aperture of the apparatus is generally not less than 30mm and the resolution is not less than 5×106cm-1.

5 Test sample

5.1 Dimension requirements: The sample shall be larger than the effective aperture of the light hole, with a thickness of not less than 2mm.

5.2 Processing requirements: The sample shall be processed into a parallel plate, and two smooth surfaces shall be polished with the surface defect V. As for the surface shape, the aperture N shall not be greater than 1, the local aperture ∆N shall not be greater than 0.5, and the parallelism shall not be greater than 1'. The rest surfaces shall be finely ground.

Foreword i
1 Scope
2 Terms and definitions
3 Test principle
4 Test equipment
5 Test sample
6 Test Environment
7 Test procedures
8 Data processing
9 Measurement uncertainty
10 Test report
Annex A (Informative) Test report of infrared transmittance for infrared optical glass