BRDF / BTDF Measurement

In collaboration with the Measurement Standards Laboratory of New Zealand, PSI has developed a goniospectrophotometer for the measurement of Bi-directional Reflectance/Transmittance Distribution Functions. The system features:
    • Tuneable monochromatic input beam with polarizer and monitoring detector;
    • 6-axis robot for sample positioning and rotation in 3 axes;
    • Precision slew ring for detector motion;
    • Software control and coordination of all measurement functions.
Measurements of BRDT/BTDF are used for characterisation of the appearance of surfaces. This involves illuminating the sample in multiple directions often over the full hemisphere of angles over the surface and then measuring the reflected light over the full hemisphere of angles from the surface.
From this the sample can be classified in terms of whether its appearance is diffuse, glossy, specular, etc. The same also applies for whether a sample’s transmittance is diffuse, hazy, regular, etc.

Furthermore, because the input beam is monochromatic and can be tuned to different wavelengths, the sample’s spectral reflectance can be analysed as well as any fluorescence effects.

These measurements have a wide range of applications including:
Characterisation of the appearance of motor vehicle coatings;
Evaluation of the appearance of foods;
Creating models for surfaces (textiles, skin, plants etc.) for use in simulations such as animated films.

As such the BRDF and BTDF measurement systems are used intensively by the automotive, consumer and entertainment industries.

Senior Research Scientist at the Measurement Standards Laboratory of New Zealand Dr Annette Koo says “The goniospectrophotometer that we developed in conjunction with PSI has enabled us to realise an independent scale of absolute reflectance and transmittance for both regular and diffuse materials. We can now offer a wide range of services characterising materials such as diffusers, gonio-apparent materials, reference colour standards (including ceramics, opal and spectralon), optical coatings, transmittance haze standards and many more.”

In addition to the high-end application shown in this example, PSI can also manufacture the BRDF/BTDF measurement equipment in a range of sizes with different configurations, broadband sources, multiple detector options, etc. See also the BiRT BRDF measurement systems [here].

For more information please contact one of our sales/applications engineers.