High-precision frequency-domain measurements of the optical properties of turbid media

We report high-precision measurements of the absorption and the reduced sca ttering coefficients for turbid media. Using a frequency-domain measurement technique for a point-source infinite-medium geometry, we find that the st andard deviations of multiple measurements of the absorption coefficient mu (a), and the reduced scattering coefficient mu(s)' are less than 0.6%, and three independently derived values for mu(a) and mu(s)' agree to better tha n 1%. Measurements of mu(a) agree with measurements of a nonscattering medi um to within 1.2%. To obtain high precision requires attention to proper co nditions for the spherical photon-density wave model, the detection lineari ty, and the ratio of the absorption rate to the source modulation rate. Fre quency-domain amplitude and phase measurements deviate from fitted curves b y 0.1% and 0.06 degrees rms, respectively. (C) 1999 Optical Society of Amer ica OCIS codes: 170.5270, 170.5280, 170.7050, 290.1990, 170.6510, 290.4210.