We present both experimental measurements and Monte-Carlo-based simulations
of the diffusely backscattered intensity patterns that arise from illumina
ting a turbid medium with a polarized laser beam. It is rigorously shown th
at, because of axial symmetry of the system, only seven elements of the eff
ective backscattering Mueller matrix are independent. A new numerical metho
d that allows simultaneous calculation of all 16 elements of the two-dimens
ional Mueller matrix is used. To validate our method we compared calculatio
ns to measurements from a turbid medium that consisted of polystyrene spher
es of different sizes and concentrations in deionized water. The experiment
al and numerical results are in excellent agreement. (C) 1999 Optical Socie
ty of America.