Properties of the light emerging from a diffusive medium: angular dependence and flux at the external boundary

By using the diffusion approximation of the radiative transfer equation and the partial-current boundary condition, an analytical expression for the a ngular dependence of the specific intensity emerging from a diffusive mediu m has been obtained. The analytical expression for the angular distribution has been validated by comparisons with the results of Monte Carlo simulati ons. By using the diffusion equation and the extrapolated boundary conditio n, an heuristic analytical expression for the diffuse time-resolved reflect ance has also been obtained by assuming that the photon flux is simply prop ortional to the fluence rate. For the case of the semi-infinite medium, com parisons with Monte Carlo results are presented and time-resolved reflectan ce data are fitted with the simple fluence rate formula. The results obtain ed show that the simple expression correctly describes the time-resolved re flectance giving an error in the retrieved optical parameters smaller than that of other commonly used expressions.