Imaging of Turbid Media with a Spatial Filter

Abstract

A buried object inside a turbid medium was imaged using a continuous-wave laser of 5-mW output power and a spatial filter. The spatial filter consists of a lens of 4-cm focal length and a pinhole of 10-μm diameter. A lock-in amplifier was used to reduce the noise. An absorbing rod of 2-mm diameter was buried in the center of a 5-cm thick cuvette filled with polystyrene spheres solution. The object was detected with a contrast of 99% when the turbid medium was 20 mean free path thick, and 10% when 30 mean free path thick.