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Monte Carlo Simulation of Light Propagation in Apples

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  2007 ASAE Annual Meeting  073058.(doi:10.13031/2013.23178)
Authors:   Jianwei Qin, Renfu Lu
Keywords:   Hyperspectral imaging; Optical properties; Fruits; Light propagation; Monte Carlo simulation

This paper reports on the investigation of light propagation in fresh apples in the visible and short-wave near-infrared region using Monte Carlo simulations. Optical properties of ‘Golden Delicious’ apples were determined over the spectral range of 500-1100 nm using a hyperspectral imaging method, and they were used in Monte Carlo (MC) models to simulate light propagation in fruit tissue. MC simulation models were validated by comparing with the diffusion theory model and experimental data. The patterns of diffuse reflectance, internal absorption, and penetration depth were determined using typical values of the absorption and reduced scattering coefficients (µa and µs’) for the apples. Up to 58.2% of the photons were absorbed under the maximum absorption condition, and 97.8% photons exited as diffuse reflectance for the zero absorption cases. The optimum sensing range for the apple samples under our imaging system setup was found to be 13 mm for the ‘Golden Delicious’ apples. Fruit tissue with a larger µa value absorbed light energy rapidly in short depth and radial distances, and light in the tissue with small µs’ value tended to propagate forward to the deeper area of the sample. Light penetration depths in ‘Golden Delicious’ apples were in the range of 2.9 to 11.3 mm over the 500-1000 nm spectral range. Pigments and water in fruit tissue greatly influenced light penetration depth.

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