Research On Theories And Experiments Of Composition Concentration Measurement Of Turbid Media With Variable Transform Method

The spectroscopy techniques based on the nature of light have been widely used in various fields of productive practices. However, the chemical composition detection techniques in turbid media have not been able to be effectively developed. The main reason is that the optical path in turbid media shows tortuous shape due to the influence of scattering particles. In this case, if the Lambert-Beer law is applied in the coexistence system of absorption and scattering, it will result in relatively low precision and inaccurate measurement, which restricts the application of spectroscopy techniques in the detection of chemical composition in turbid media.In this paper, the problems of composition concentration measurement in turbid media are analyzed firstly and the Variable Transform (VT) method is proposed. Then, the simulation of Monte Carlo combined with the IAD algorithm, and the experiment of double-integrating-sphere system combined with IAD algorithm have been conducted to verify the feasibility to extract the scattering information from the intralipid solution. Furthermore, the linear relationship between the scattering coefficient and the concentration of Intralipid has been established. Experimental results show that, detection the composition concentration in turbid media by the VT method is effective and feasible, and the relative error to predict the concentration of Intralipid is within 10%.Based on above studies, the optimal detection conditions of composition concentrations are investigated to improve detection accuracy. Firstly, taking the simple turbid media for example, light distribution characteristic in turbid media and the significance of optimal detection conditions are discussed. Secondly, based on diffusion theory, optimal detection conditions on diffuse reflectance measurement are analyzed, and the optimal detection distance of the simple turbid media are calculated through Monte Carlo simulation and diffusion theory. In addition, the expressions of optimal detection distance for turbid media with different concentrations are obtained according to the evaluation function of optimal detection conditions on diffuse reflectance. Finally, the optimal detection conditions on diffuse transmittance measurement are discussed. The expressions of optimal thickness for turbid media with different concentrations are obtained according to the evaluation function of optimal detection conditions, and the measuring accuracy applying the optimal thickness is conducted particularly. Results show that, the optimal detection conditions will further improve the measuring accuracy of component concentration in turbid media and establish a foundation for the research for the complicated turbid media.