Integrating sphere system is designed and constructed for multiple optical properties measurement

An integrating sphere system has been developed and built to measure various optical properties in the infrared spectral region of the visible spectrum.

This is especially true with specular samples, where you can measure the absolute transmittance and reflectance directly and with great precision.

The absorptance may be calculated from these values using a straightforward formula—the integrating sphere widely used for many optical properties measurements.

Working for many optical properties measurements

For many opaque and transmitting materials samples, the Fourier transform spectrophotometer is used to quantify these characteristics. Most of the detector-limited working spectral range of 2 m to 18 m is demonstrated to have enlarged uncertainties of less than 0.003 (absolute) for the measurements with the expanded uncertainties.

The sphere is controlled via two rotation phases, which allow the ports on the sphere to be reconfigured in any orientation relative to the input beam, depending on the direction of the input beam. The spherical system is intended for infrared spectral measurements only; nevertheless, the measurement technique, system design concepts, and system characteristics are usually applicable to other wavelengths.

Main optical properties to measure

It has been common practice to utilize integrating spheres to evaluate diffuse reflectance and transmittance of materials in the ultraviolet, visible, and near-infrared spectral ranges. More recently, in the mid-to far-infrared fields, dating as far back as the 1970s. However, the application of integrating spheres for the particular measurement of specular materials has been rare.

However, this is the case even though the theoretically predicted ratio of two observations for a perfect sphere would lead to the absolute reflectance of a specular sample. Real integrating spheres aren’t perfect, which is why they’re not used for specular reflectance measurements using integrating spheres. Because of this, no sphere-wall coating can ever be used as a perfect Lambertian diffuser. Additionally, baffles may alter the light distribution within the sphere. The accuracy of the sphere equations may be significantly affected by these and other deviations from a perfect sphere.

Designing a device for absolute transmission, reflectance, and absorptance measurement of specular samples utilizes the integrating sphere’s advantages for more precise light detection. An example of how the technique works is using IR windows and mirror characterization.

Because you can calculate the absolute measurement error for non-absorbing spectral areas directly, the ability to measure both transmittance and reflectance in the same geometry provides accurate uncertainty estimates for findings beyond these regions. The use of the integrating sphere eliminates many significant sources of measurement error, allowing the levels of precision shown in this article after considerable study and deliberation. LISUN has the best integrating sphere system for measuring optical properties.

Although it’s a good idea, direct installation on the sphere isn’t necessary for specular sample characterization. However, as shown in this work, placing the sample directly on the sphere has two significant benefits. To characterize non-ideal samples, these two papers are relevant. About the worst samples, the new design can tolerate more beam deflection, deviation, distortion, and focus shift than previous ones could. In addition, measurements may be made on not entirely specular materials but do show some scatter.