What is Total Integrated Scattering?

1. Measuring TIS using integrating spheres

You can measure the TIS of a material sample or a surface using specially designed integrating spheres. Ideally the measurement setup should measure all of the scattered light signal (without the specular) into a hemisphere: the scattered light from the sample is integrated by a Lambertian reflective hemisphere, then normalized by the total reflected and transmitted power of the incident beam (also measured into a reflective hemisphere).

In practice, the sample is placed on the exit and then entrance port of an integrated sphere and illuminated by a laser source to measure the (specular reflectance power + diffuse transmittance power ) and the (diffuse reflectance power + specular transmittance power), respectively. The same measurement is performed again after opening a port that permits the specular beam out of the integrating sphere so that it is not included in the measurements of the diffuse transmittance power and the diffuse reflectance power.

2. Measuring TIS from BSDF

TIS can also be measured by using a goniometer with a detector that can be scanned in angular space to measure the BSDF of a sample or surface. TIS can be calculated directly from BSDF measurements as shown in the following formulas.