An Analysis of the Nonlinear Spectral Mixing of Didymium and Sodalime Glass Beads Using Hyperspectral Imagery (HSI) Microscopy

Nonlinear spectral mixing occurs when materials are intimately mixed. Intimate mixing is a common characteristic of granular materials. A linear spectral unmixing inversion applied to a nonlinear mixture yields subpixel abundance estimates that do not equal the true values of the mixture's components. Several methods to invert nonlinear spectral mixtures have been proposed. There is, however, a paucity of real spectral image data sets that contain well characterized intimate mixtures. To address this, special materials were custom fabricated, mechanically mixed to form intimate mixtures, and measured with a hyperspectral imagery (HSI) microscope. The results of analyses of visible/near-infrared HSI microscopy image cubes of intimate mixtures of the two materials are presented. The materials are described as the numerous unmixing algorithms applied to the HSI data of the mixtures. Abundance estimates varied widely.