Using polarization to find a source in a turbid medium.

We study multiple scattering of partially polarized light using the theory of radiative transport. In particular, we study the light that exits a half-space composed of a uniform absorbing and scattering medium due to an unpolarized, isotropic, and continuous planar source. We assume that Rayleigh scattering applies. Using only angular integrals of the two orthogonal polarization components of the intensity exiting the half-space, we recover the depth and the strength of this source in two stages. First, we recover the depth of the source through the solution of a one-dimensional nonlinear equation. Then we recover the strength of the source through the solution of a linear least-squares problem. This method is limited to sources located at depths on the order of a transport mean-free path or less. Beyond that depth, these data do not contain sufficient polarization diversity for this inversion method to work. In addition, we show that this method is sensitive to instrument noise. We present numerical results to validate these results.