Effects of optical variables in a single integrating sphere system on estimation of scattering properties of turbid media. (June 2020) - Hu, Dong
Abstract : This research was aimed at determining the effect of optical variables for a single integrating sphere system, coupled with the inverse adding-doubling method, on estimating the reduced scattering coefficient ( μ s ′ ) of turbid media. Integrating sphere measurements were performed on a total of 36 liquid samples and two solid samples. The results demonstrated that the system had good accuracy, with average errors for estimating absorption coefficient μ a (pure absorption) and μ s ′ (pure scattering) of liquid samples being 15.0% and 4.7% over 550–900 nm, compared with the collimated transmittance and empirical equation, respectively. The system also had good reproducibility for μ a and μ s ′, with the coefficients of variation lower than 4%. Sensitivity analysis revealed that the detectable values of μ a and μ s ′ were around 0.02 cm −1 and 4.5 cm −1 . Entrance and detector port diameters, standard reflectivity and anisotropy factor had a negligible effect on estimating μ s ′ (<2.2%). However, refractive indices of sample and cuvette, sphere wall reflectivity, beam diameter and its position, and specular reflectance had a relatively large effect on the estimation of μ s ′ (2.8%–35.3%). Hence these variables should be carefully chosen or accurately measured before optical property measurements are carried out. Application examples of the μ s ′ estimation for apple skin and flesh further validated the system performance, indicating that appropriate selection of optical variables could improve the estimation of μ s ′ . Highlights: A single integrating sphere (SIS) system was constructed. Accuracy, reproducibility and sensitivity of SIS system was assessed. Effects of optical variables on estimating reduced scattering coefficient ( μ s ′ ) investigated. The μ s ′ of apple skin and flesh samples were estimated separately.