Experimental and theoretical study of light propagation in the apple tissues : application to an optical process of laser spectroscopy spatially resolved ; Etude expérimentale et théorique de la propagation de la lumière dans les tissus de la pomme : application à un procédé de spectroscopie laser résolue dans l'espace

Light interaction with biological materials such as fruits and vegetables is a complex phenomenon involving both absorption and scattering of light within their structures (flesh and skin). In order to estimate the skin effect on the light propagation in apple samples, experimental and numerical studies have been carried out. A multispectral imaging system (633, 763, 784 and 852 nm) was developed to capture backscattered images of whole, cut apple, with and without skin (Granny Smith, Royal Gala and Golden Delicious). The originality of the instrument is due to the reconstruction of the backscattered signals (initially saturated) and to retrieve the internal optical properties (μa and μ's) optimized by inverse method. The numerical investigation is mainly based on the stochastic Monte Carlo method. The apple sample is simulated as a sphere comprising the flesh surrounded by a thin layer (skin). The input data was retrieved experimentally. A comparison between experimental and numerical data was performed by considering the two tissue arrangements (i.e. whole and half cut apples), with and without skin. These investigations show that the skin strongly influences the light propagation in apples close to the optical axis. Finally, a study focused on the search for correlations between recovered optical parameters (μa and μ's) and mechanical or rheological parameters. It has been shown that the reduced scattering coefficient (μ's) is able to predict the apple firmness. Correlations were also established between the optical properties (μa, μ's and μeff) and both elastic (G') and viscous (G'') moduli of apple purees. ; L’interaction de la lumière avec des matériaux biologiques tels que les fruits et légumes est un phénomène complexe qui implique l'absorption et la diffusion de la lumière dans leurs structures (chair et peau). Afin d'estimer l’effet de la peau sur la propagation de la lumière dans des échantillons de pommes, des études expérimentales et numériques ont été menées. Un système d'imagerie multispectrale ...