Banknote Characterization using a Thermal Infrared ‘THz Torch’ Spectrometer

In this paper, a thermal infrared spectrometer based on the ‘THz Torch’ concept is reported and used to characterize both paper and plastic banknotes. The spectrometer consists of a thermal infrared emitter with near-ideal blackbody radiation characteristics and a low-noise pyroelectric detector. A filter bank with 16 narrow band-pass optical coating filters is selected to define a coarse set of 16 discrete spectral data points between 20 to 80 THz. Both transmission and reflection modes of operation are demonstrated ‘over the THz horizon’ (within the extended THz range). This work shows the potential of this emerging lowcost technology for non-destructive and non-invasive testing, material characterization, material identification from a precharacterized database, process variation monitoring and gas sensing.