Advanced SWIR Spectroscopy for Enhanced Currency Verification
Hyperspectral cameras, particularly the Grand-EOS with its tunability from 400 to 1650 nm, are crucial for precise counterfeit detection by capturing images across various wavelengths, revealing unique spectral signatures of inks and materials in banknotes. Hyperspectral testing ensures consistent data quality through meticulous control over illumination and calibration with white and dark reference images. This technology can detect subtle differences in inks and materials, enabling accurate identification of even high-fidelity counterfeit notes and enhancing forensic analysis practices.
Case Study 1: Inkjet Printer Ink Analysis
We conducted an ink test using four different printers and their respective ink cartridges to validate the power of HSI in ink differentiation:
Printers and Inks:
HP Envy 4520 with Inktopia 64XL ink
Brother MFC J47SDW with Odoga B-103(101) ink
Xerox Workcentre 6515 with LD Product CXE6510SET5AMZ ink
Epson-276C with Epson-220 ink
Key Findings:
CMYK Base Colors: The fine spectral signature of CMYK base colors for inkjet printers varies depending on the origin and supplier of the ink. The different inks can be easily distinguished and identified.
SWIR Analysis: Most inks vanish in the short-wave infrared spectrum, except for one family of black ink. Visible CMOS sensors can be effectively used in this application without the need to use more expensive SWIR cameras.
Grand-EOS Capability: The Grand-EOS system can extract the fine spectral signature from any pixel within its field of view. There is no need to move the object under examination during the acquisition of hyperspectral data.
Case Study 2: Analysis of ‘Montesquieu’ Banknotes
We analyzed ‘Montesquieu’ banknotes (200 French Francs), which were created in 1981, first emitted in 1982, discontinued in 1994, and retired from distribution in 1998. Two banknotes were purchased from collectors in 2020: one genuine and one fake.
Key Findings:
VIS and SWIR hyperspectral wide-field imaging can reveal significant differences in seemingly identical banknotes that cannot be detected by the human eye.
The technique can identify even high-fidelity counterfeit banknotes comparing spectral signatures one different areas of the notes
PCA analysis in the VIS and the SWIR further enhances the spectral differences between the two banknotes making the detection of counterfeit banknotes more obvious.
Combined with the analysis of inks from the first part of our study and with a proper reference database, this means that one could determine which printer was used to print each individual banknote and trace the origin of the banknote.
Results obtained with the GRAND-EOS
The Grand-EOS hyperspectral imaging system proves to be a powerful tool in identifying counterfeit banknotes. This technique can distinguish even high-fidelity counterfeit notes by revealing minute differences in the spectral response of inks and materials used.
Additional powerful techniques, such as UV fluorescence, can be added to the Grand-EOS to enhance its ability to detect minute details and differences. VIS/SWIR hyperspectral imaging is not limited to ink and paper; it can also identify colors, organic traces, and fabrics (e.g., cotton vs. nylon vs. polyester). Moreover, VIS/SWIR hyperspectral imaging can detect residual traces of chemicals on the paper, such as acetone, hydrocarbons, or other solvents.
Hyperspectral cameras hold the promise of a more secure and accurate future in counterfeit detection. Advances in technology and methodology empower the industry to meet the challenges of sophisticated counterfeiting, ushering in a new era of precision and efficiency in currency verification.
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