Apertures integrating spheres

Following the reference and dark scans, the working sample is placed against the aperture of the integrating sphere. The spectrometer then determines the amount of light reflected by the sample by comparison against the reference standard. 

Diffuse transmission may also be collected using integrating sphere based DRA. To perform this measurement, we place the sample on the entrance aperture designed for the sample beam and cover the sample aperture with the standard high reflectivity sample. The baseline and dark current are collected exactly like the non-diffuse transmittance and analysis is the same as diffuse reflectance. 

The output aperture of an integrating sphere is a Lambertian, uniform source for which we can predict" the flux 4>out, exitance M, and radiance L. We find the formulas inferred in various vendor s writeups a bit unclear, but Equations 9.3a-9.3c are consistent with them in the terminology and notation of our Chapter 2. 

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