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Measuring the optical properties of two-layer agricultural tissue with a sequential method from spatially-resolved diffuse reflectance, Part I: Analysis and simplification
Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org
Citation: 2018 ASABE Annual International Meeting 1800612.(doi:10.13031/aim.201800612)
Authors: Aichen Wang, Renfu Lu, Lijuan Xie
Keywords: Diffusion-P3 model, optical property, sequential method, spatially-resolved, two-layer tissue
Abstract. Accurate quantification of the optical properties of two-layer agricultural tissues is of great importance for the quality detection with optical methods. In this work, a simple diffusion-P3 hybrid model was firstly proposed and optimized for extracting the optical properties of top layer. The ‘joint point‘ for the hybrid model was optimally suggested to be 2.5 mfp1'. Secondly, the factors that affect the extraction of the optical properties of top layer, including top layer thickness (d), mfp1'/mfp2', μa1/μa2, and μs1'/μa1, were analyzed. The effect of these factors can be concluded as three independent ones, i.e., d, μeff1/μeff2, and μs1'/μa1. It was found that with close d/mfp1' value, the -10% relative error contours for estimating the optical properties were similar for different samples. For the value of μa1/μa2 greater than 1, which is true for most agricultural products, the relative error contours of different samples shared common optimal regions. With respect to μs1'/μa1, benefitting from the high precision of diffusion-P3 hybrid model on describing light propagation for small source-detector separations, the effect of μs1'/μa1 was mild. Based these findings, the number of factors was reduced and the parameter estimation procedure can be simplified. The effect of μa1 /μa1=2 was ignored and the effect of mfp1'/mfp2' was significant only for extreme large and small mfp1'/mfp2' values, which was not applicable for the same type of agricultural products. And the effect of μs1'/μa1 was also ignored. This work laid a foundation for the practical implementation of the sequential method for measuring the optical properties of two-layer tissue from spatially-resolved diffuse reflectance.
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