Influences of the scattering phase functions on spatially resolved diffuse reflectance from a homogenous semi-infinite medium close to source are studied with Monte Carlo simulation. It is shown that the influences of optical parameters higher than the second order on the diffuse reflectance are quite weak in the region from 0.3 to several transport mean free pathes when Henyey-Greenstein phase function or a combined phase function of two parameters are used. But this influence may be substantial if the double Henyey-Greenstein function is used to describe the scattering property of tissue.

Steady-state diffuse reflectance based on P3 approximation is studied at short source-detector separations. In many practical applications, we can only measure the diffuse reflectance light close to the source, and attempt to derive the optical parameters of tissues from the collected data. In this paper, diffuse reflectance with different absorption coefficients and scattering coefficients at short source-detector separations is measured, and the experimental results are compared with that of P3 approximation. These studies show that P3 approximation can be used to describe the light contribution close to the source, and can be used to study strong absorption medium.