BS ISO 17328:2014 pdf download.Optics and photonics — Optical materials and components — Test method for refractive index of infrared optical materials
This International Standard provides a standard method for measuring the relative refractive index to the air of Infrared materials used In the Infrared spectral range from 0.78 pm to 25 pm.
The sco of this International Standard excludes methods for measuring the refractive index of birefringent materials and methods for measuring the complex refractive index,
2 Normative references
The following documents, in whole or In part, are normatively referenced In this document and are Indispensable for Its application For dated references, only the edition cited applies. For undated references, the latest edition o4 the referenced document (including any amendments) applies.
ISO 11382:2010, Optics and photonics — Optical materials and components — Characterization of optical materials used in the infrared spectral range from 0.78 jim to 25 pm
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
refractive index
absolute relractive index
ratio of the velocity of the electromagnetic waves at a specific wavelength in a vacuum to the velocity of the waves in the material
IS0URCI: ISO 12123:2010,3.11
3.2
relative refractive index
ratio of the (absolute) refractive index of the material of the specimen to the (absolute) refractive index of the material in contact with the specimen at a specific wavelength
3.3
angle of minimum deviation
angle between the ray incident upon the specimen prism and the ray exiting the specimen prism at its minimum value, which occurs when the ray inside the specimen prism makes equal angles with the entrance and exit faces of the specimen prism
4 Method for measuring
4.1 General
In this International Standard, the technique of the minimum deviation method (or measuring refractive index is described.
The minimum deviation method shall be applied for measuring refractive index.
4.3 Apparatus and procedure for measurement
The apparatus for measurement shall be equipped with the following:
a) a method to emit a collimated monochromatic light beam of specified wavelength to the specimen prism;
b) a method to vary the angle of the collimated monochromatic light beam to the entrance face of the specimen prism;
c) a method to determine the direction of the monochromatic light beam refracted by the specimen prism;
d) a method to indicate the angle of minimum deviation δ;
e) a method to measure the temperature of the specimen prism.
Examples of apparatus for measurement of the angle of minimum deviation are shown in Annex A. A procedure for measurement is also described in Annex A. In addition, the absolute value of the angle of deviation error is described in Annex B.
NOTE See Figure 1.
4.4 Wavelength of light beam for measurement
The wavelengths of measurement shall adequately sample the spectral range of interest to enable curve fitting of the data to a dispersion formula, allowing calculation of the relative refractive index at any arbitrary wavelength within the spectral range.
5 Specimens
5.1 The shape and dimensions of the specimen prism
The specimen shall be a wedged prism made of the material to be measured. The entrance face and the exit face shall be polished.
An example of the shape of the specimen prism is shown in Figure 3. The optimum apex angle (such that error in measurement of the apex angle is least severe) for a material of the relative refractive index n rel is α = 2arctan(1/n rel ) (2)
For low index materials, this relation can result in undesirably large apex angles; this relation shall be used as guidance.
5.2 Surface accuracy
The surface accuracy of the entrance face and the exit face of the specimen prism shall be measured with an interferometer. Any measured power term shall not be subtracted from measurement data. A surface flatness error should be 150 nm P-V or less over the entire clear aperture of the specimen prism faces.
6 Test report
The test report shall specify the following:
a) specimen name in accordance with ISO 11382:2010, 5.6;BS ISO 17328 pdf download.BS ISO 17328-2014 pdf download
