Analytic evaluation of diffuse fluence error in multi-layer scattering media with discontinuous refractive index

TL;DR

This paper introduces an analytic method to estimate errors in diffuse radiation calculations across media with different refractive indices, avoiding complex simulations and highlighting error significance in specific scattering conditions.

Contribution

It presents a simple analytic approach for evaluating diffuse fluence errors at boundaries between scattering media with discontinuous refractive indices, applicable to multilayer systems.

Findings

Error is significant in forward-biased scattering media with absorption.

Cumulative errors increase in multilayer media with refractive index changes.

The method enables quick error estimation without Monte Carlo simulations.

Abstract

A simple analytic method of estimating the error involved in using an approximate boundary condition for diffuse radiation in two adjoining scattering media with differing refractive index is presented. The method is based on asymptotic planar fluences and enables the relative error to be readily evaluated without recourse to Monte Carlo simulation. Three examples of its application are considered: (1) evaluating the error in calculating the diffuse fluences at a boundary between two media with differing refractive index and dissimilar scattering properties (2) the dependence of the relative error in a multilayer medium with discontinuous refractive index on the ratio of the reduced scattering coefficient to the absorption coefficient ms'/ma (3) the parametric dependence of the error in the radiant flux Js at the surface of a three-layer medium. The error is significant for strongly forward biased scattering media with non-negligible absorption and is cumulative in multi-layered media with refractive index increments between layers.