Laser-induced fluorescence and hyperspectral imaging integrated in one sensor system - the inSPECtor project

Optical spectroscopy-based methods provide an immense potential for identifying rock compositions in a non-invasive and highly efficient manner, which is crucial for innovative, sustainable and acceptable technologies in raw material exploration. In principle, we employ two fundamental types from the set of light-material interactions light absorption used for hyperspectral imaging (HSI), and light emission used for laser-induced fluorescence (LiF) spectroscopy. The light spectra measured after illumination may be used as fingerprints of a sample’s composition, as long as the characteristic spectral features are known and distinguishable.
In the inSPECtor project, we develop an integrated sensor system that combines the two types of spectroscopy in order to increase the range of detectable materials and the robustness of results. HSI has already proven successful for the mapping of various minerals and also of some REEs such as Nd. However, the complexity of natural samples leads to mixed spectra with masked or only weak REE-related features complicating or even precluding a robust identification of many other REEs. Here, LiF spectroscopy provides a much more sensitive alternative as REEs show very distinct emission features characteristic transitions in REE3+ ions, as encountered in typical REE-containing minerals.
Here, we present how the inSPECtor project combines the potential of both HSI and LiF, especially for REE identification. We focus on the qualitative aspects of REE characterization in synthetic REE standards, in natural minerals and complex rocks from a range of typical REE-mineral deposits. Based on the characterization and successful identification of Nd3+, Pr3+, Sm3+, Eu3+, Yb3+, Ho3+, Dy3+, Er3+, Tb3+ and Tm3+ , we summarize required sensor specifications and illustrate needed data analyses routines.