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 low-cost technology for non-destructive and non-invasive testing, material characterization, material identification from a pre-characterized database, process variation monitoring and gas sensing.