The effect of light losses in double integrating spheres on optical properties estimation

The double integrating sphere setup (DIS) measures diffuse reflectance, dif fuse transmittance and collimated transmittance, from which the optical pro perties of tissue (the absorption coefficient mu(a), the scattering coeffic ient mu(s) and the anisotropy of scattering g) are estimated. The effect of light losses in the DIS and optical thickness on optical properties estima tion by the inverse adding doubling algorithm (IAD) and uniqueness of measu rement have been investigated using a Monte Carlo method. Results were obta ined for optical properties in turbid tissues (0.80 less than or equal to a lbedo less than or equal to 0.99, 0.80 less than or equal to anisotropy les s than or equal to 0.99, 1.5 less than or equal to optical thickness less t han or equal to 7.5) sandwiched between glass slides. At optical thickness = 6.0 the loss of light through the glass slides is ranging from 13% +/- 0. 5% (at albedo = 0.80) to 15% +/- 0.5% (at albedo = 0.98) of the incident po wer. The loss of light at the exit port in the transmittance sphere is incr easing upto 50% of the incident power at highly forward scattering. These l osses result in a dependency on optical thickness of the optical properties estimation by the IAD algorithm. Furthermore, because of these losses, the DIS setup measurement Is found to be fundamentally nonunique, when simulta neously measuring the diffuse reflectance, diffuse transmittance and collim ated transmittance.