SYSTEM FOR IDENTIFYING MATERIALS BY NIR SPECTROMETRY

摘要

In a method for identifying an unknown product a library of absorbance spectra of known products is measured and stored in a library. A quick search using clustering techniques is conducted to narrow the search to a few products, followed by an exhaustive search of the spectra of the few products. More specifically, principal component analysis is applied to the absorbance spectra to generate product score vectors extending into principal component inside model space which are divided into clusters and subclusters in accordance with their relative proximity. Hyperspheres are constructed around each vector and an envelope is constructed to enclose each cluster surrounding the hyperspheres within the cluster. The absorbance spectrum of the unknown product to be identified is measured and an unknown product score vector is determined from the unknown product spectrum projecting in principal component inside model space of the clusters. It is determined whether or not the unknown product score vector falls within one of the envelopes and if so the product score vector is projected into the principal component inside model space of that cluster and it is determined whether or not the unknown product score vector falls within any of the subclusters divided from the cluster. This process is repeated until the unknown product score vector is found to lie in a cluster which is not further subdivided. In this manner, the search is narrowed to a few products. An exhaustive search is then carried out to match the spectrum of the unknown product with the spectra of the known products corresponding to the undivided subcluster.