@article{pickering92,
  author = {J. W. Pickering and C. J. M. Moes and H. J. C. M. Sterenborg and S. A. Prahl and M. J. C. van Gemert},
  title = {Two Integrating Sphere with an Intervening Scattering Sample},
  journal = {J. Opt. Soc. Am. A},
  year = {1992},
  volume = {9},
  pages = {621--631},
  abstract = {Two integrating spheres placed so that the exit port of one and the entry port of the other are adjacent, with only a sample intervening, will allow the simultaneous determination of the reflectance and transmittance of the sample. Such a geometry allows measurements to be made as the sample undergoes some external stimulation, such as heat, pressure, or a chemical change. To determine the sample reflectance and transmittance from the measured values of irradiance within each sphere requires the calculation of the exchange of light through the sample between the spheres. First the power collected by a detector situated in the wall of an integrating sphere is calculated as a function of the area and reflectance of the wall, holes, sample, and detector for both diffuse and collimated light incident on the sample, and for a sample located at either the exit port (reflectance) or the entry port (transmittance) of the sphere. Next, using the single sphere equations, the effect of the multiple exchange of light between two integrating spheres, arranged so that the sample is placed between them, is calculated. In all cases of two integrating spheres the power detected is greater than or equal to that for the single sphere and depends on both the reflection and transmission properties of the sample. Additionally, the effect of a baffle placed between the sample and detector or of a non-isotropic detector is to reduce the power detected.},
}