Laser photothermal diagnostics of genuine and counterfeit British and United States banknotes

Abstract

Laser-induced, frequency-scanned IR photothermal radiometry was used to investigate the thermophysical properties of the paper on which several genuine and counterfeit British (pound 10) and U.S. ($50, $100) currency bills were printed. The radiometric photothermal amplitudes and phases were further compared with a theoretical model, which yielded simultaneous quantitative measurements of the thermal diffusivities and conductivities of the bills. Both statistical and single-specimen results demonstrated the excellent thermophysical resolution of the technique with prospects for its use in the nonintrusive, on-line identification of counterfeit banknotes. (C) 1997 Society of Photo-Optical Instrumentation Engineers.