Optical characterization of biological tissues is of real interest to improve medical diagnosis and in particular in the detection of precancerous tissues. The reduced scattering coefficient micro's and the absorption coefficient microa are the most commonly retrieved coefficients. Some methods also allow to obtain the anisotropy factor g, but only few of them are non-invasive. We propose a new non-invasive method allowing the estimation of the anisotropy factor and the reduced scattering coefficient. This method is based on the image analysis of the Q-element of Stokes vector backscattered from the turbid medium. These Q-element images show specific patterns depending on g, and micro's is determined by the size of the patterns. Therefore the use of Fourier Descriptors (FD) on simulated and experimental data, to discriminate the specific geometrical features of the Q-element, enabled us to determine the anisotropy factor and the scattering coefficient.