Validity conditions for the radiative transfer equation

Luis Martı́-López, Jorge Bouza-Domı́nguez, Jeremy C. Hebden, Simon R. Arridge, René A. Martı́nez-Celorio
2003 Optical Society of America. Journal A: Optics, Image Science, and Vision  
We compare the radiative transfer equation for media with constant refractive index with the radiative transfer equation for media with spatially varying refractive indices [J. Opt. A Pure App. Opt. 1, L1 (1999)] and obtain approximate conditions under which the former equation is accurate for modeling light propagation in scattering media with spatially varying refractive indices. These conditions impose restrictions on the variations of the refractive index, the gradient of the refractive
more » ... the refractive index, the divergence of the rays, the frequency of modulation, and the widths of light pulses, which are related to the mean refractive index, the absorption coefficient, and the reduced scattering coefficient of the medium. Each condition is geometrically interpreted. Some implications of the results are discussed.
doi:10.1364/josaa.20.002046 pmid:14620333 fatcat:g2vmsogshjch5jvgaif6c7gske