Influence of Surface-Induced Nonuniform Reflectance on the Diffuse Reflectance Factor Part Ⅰ: Model Predictions

摘要

The Kubelka-Munk (KM) model is used frequently as a tool to design paper to reach a desired opacity and whiteness. The input data in this modelling, the scattering and absorption coefficients, are commonly derived from diffuse reflectance factor measurements. The quality of the coefficient values is dependent on the structure of the samples and the backings from which they were obtained. In this paper, we focus on modelling the influence of non-uniform reflectance induced by the surface structure, and how it affects the diffuse reflectance factors obtained using the d/0° standardized measurement geometry. From the analysis, we conclude that the structure of the surface facing the detector may have a significant effect on the instrument readings depending on whether the sample is glossy or reflects diffusely from the surface. Based on this surface reflectance, we analyze various situations of relevance for the papermaker, and show that common-practice application of the KM model to reflectance factor measurements may lead to serious misinterpretations.