Abstract
Ink analysis is an important tool in forensic science and document analysis. Hyperspectral imaging (HSI) captures large number of narrowband images across the electromagnetic spectrum. HSI is one of the non-invasive tools used in forensic document analysis, especially for ink analysis. The substantial information from multiple bands in HSI images empowers us to make non-destructive diagnosis and identification of forensic evidence in questioned documents. The presence of numerous band information in HSI data makes processing and storing becomes a computationally challenging task. Therefore, dimensionality reduction and visualization play a vital role in HSI data processing to achieve efficient processing and effortless understanding of the data. In this paper, an advanced approach known as t-Distributed Stochastic Neighbor embedding (t-SNE) algorithm is introduced into the ink analysis problem. t-SNE extracts the non-linear similarity features between spectra to scale them into a lower dimension. This capability of the t-SNE algorithm for ink spectral data is verified visually and quantitatively, the two-dimensional data generated by the t-SNE showed a better visualization and a greater improvement in clustering quality in comparison with Principal Component Analysis (PCA).
Highlights
Hyperspectral imaging (HSI) is a technology that captures the images in hundreds of narrow optical bands across the electromagnetic spectrum
It is easy to identify that t-Distributed Stochastic Neighbor Embedding (t-SNE) provides better visualization of Normalized Mutual Information (NMI) Homogeneity Index (HI) Completeness Index (CI) Silhouette Index (SI)
It revealed that the t-SNE outperforms Principal Component Analysis (PCA) for this specific task
Summary
Hyperspectral imaging (HSI) is a technology that captures the images in hundreds of narrow optical bands across the electromagnetic spectrum. While analyzing the types of ink in a questioned document, the presence of multiple inks may give an indication of some manipulations taken place. To get this evidence, a forensic expert needs to distinguish different inks used and this is difficult to perform visually. The human eye can detect different colors [7]; it may not differentiate colors that appear visually similar but spectrally different and this property is known as metamerism. It can be defined as; if two color stimuli have different spectral radiant power distributions but they possess a match in color for a given observer [8, p. The HSI images can vanquish this snag in the human visual system by extracting details from the abundant spectral components
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