Use of a laser beam with an oblique angle of incidence to measure the reduced scattering coefficient of a turbid medium.

A simple and quick approach is used to measure the reduced scattering coefficient (µ(s)') of a semi-infinite turbid medium having a much smaller absorption coefficient than µ(s)'. A laser beam with an oblique angle of incidence to the medium causes the center of the diffuse reflectance that is several transport mean-free paths away from the incident point to shift away from the point of incidence by an amount Δx. This amount is used to compute µ(s)' by µ(s)' = sin(α(i))/(nΔx) where n is the refractive index of the turbid medium divided by that of the incident medium and α(i) is the angle of incidence measured from the surface normal. For a turbid medium having an absorption coefficient comparable with µ(s)', a revision to the above formula is made. This method is tested theoretically by Monte Carlo simulations and experimentally by a video reflectometer.