Optical characterization of volume-scattering backgrounds

Scattering media act in many situations as backgrounds in target recognition and remote sensing and an accurate method for their characterization is highly desirable. The use of light sources with short temporal coherence produces the depth resolution needed for this purpose. The low coherence interferometry has been used, for long time, as a filter to suppress multiple light scattering and preserve the single-scattering characterized by well defined scattering angles and polarization properties. Recently, the low-coherence interferometry was successfully applied to multiple light scattering regime. The signal obtained from such a measurement relates directly to the optical path-length distribution of the backscattered light and, therefore, comprehensively characterizes the scattering system. The path-length resolved backscattering defines the scattering properties of the medium and its shape has distinct features for single and multiple-scattering regimes. In our experiments, the path-length domain is sampled with a resolution equivalent to 30 fs in conventional time-of-flight measurements. We will show that the transition domain between single and multiple scattering can be fully characterized using this methodology and that single scattering information can be successfully retrieved even in the presence of a strong multiple scattering component.