Assessment of Refractive Index of Pigments by Gaussian Fitting of Light Backscattering Data in Context of the Liquid Immersion Method
ILPO NISKANEN,* KAI-ERIK PEIPONEN, and JUKKA RÄTY
Using a multifunction spectrophotometer, the refractive index of a pigment can be estimated by measuring the backscattering of light from the pigment in immersion liquids having slightly different refractive indices. A simple theoretical Gaussian function model related to the optical path distribution is introduced that makes it possible to describe quantitatively the backscattering signal from transparent pigments using a set of only a few immersion liquids. With the aid of the data fitting by a Gaussian function, the measurement time of the refractive index of the pigment can be reduced. The backscattering measurement technique is suggested to be useful in industrial measurement environments of pigments.
Index Headings: Mineral pigments; Refractive index; Immersion method; Light scattering.
