Speckle Pattern Acquisition and Statistical Processing for Analysis of Turbid Liquids

Analysis and fine distinction of turbid fluids is challenging since standard techniques, usually applied to transparent liquids, fail to work properly due to scattering losses. The phenomenon of speckle pattern, which arises when such liquids are illuminated by coherent light, can be successfully applied to investigate the properties of these media. In this work, we exploit a simple instrumental configuration, combining a laser diode and a PC-interfaced, digital CMOS camera, for acquiring images and video of speckle pattern generated by illuminating turbid fluid samples that were obtained by dilution of opaque suspensions, such as commercial vegetable milk. By processing the acquired image sequences, we have been able to extract several statistical parameters that can be correlated with the concentration of the scattering elements of each sample, allowing an easy differentiation of the various fluids.