Theory of light transfer in food and biological materials

Authors: Lu, Renfu

Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 9/25/2015
Publication Date: 5/1/2016
Citation: Lu, R. 2016. Theory of light transfer in food and biological materials. In: Lu, R., editor. Light Scattering Technology for Food Property, Quality and Safety Assessment. Abingdon, United Kingdom: CRC Press, Taylor & Francis Group. p. 43-78.

Interpretive Summary:

Technical Abstract: In this chapter, we first define the basic radiometric quantities that are needed for describing light propagation in food and biological materials. Radiative transfer theory is then derived, according to the principle of the conservation of energy. Because the radiative transfer theory equation is generally too complex to solve, diffusion approximation theory needs to be introduced in order to simplify the mathematical description of light propagation in food and biological materials. It is then followed with the discussion of three boundary conditions commonly used for solving the diffusion equation. Moreover, analytical solutions to the diffusion equation under several special light illumination conditions are presented, which form the theoretical foundation for a number of modern noninvasive or in vivo optical property measurement techniques, including spatially-resolved, time-resolved, frequency domain, and spatial-frequency domain. Finite element method offers flexibility in dealing with complex geometries and nonhomogeneous or layered scattering media, and is useful in studying light propagation in food and biological materials. Application examples are given of using finite element method for modeling light propagation in semi-infinite scattering media and predicting the reflectance at the surface.