Visualization of flow in multiple-scattering liquids

We have performed quasi-elastic multiple-light-scattering experiments on a suspension of colloidal particles in Brownian motion into which a capillary with Poiseuille flow of the same suspension was inserted. We show that the time correlation function of the backscattered light, measured at various points on the sample surface, provides information on the position of the capillary and on the flow rate, demonstrating the possibility of imaging flow in turbid media under conditions of no static scattering contrast.