THz-TDS Confocal Imaging of Banknote Anti-counterfeiting Labels

In this paper, we demonstrate terahertz imaging of banknote anti-counterfeiting labels by using the THz-TDS confocal imaging system built in our lab. With help of this system, spatial resolution is significantly improved and detail Characters of the anti-counterfeiting labels can be identified. Areas of the multiple overlapping banknotes papers with different number of layers are imaged and distinguished by measuring the time delay and absorption of the THz pulse that transmits through banknotes papers. This technology provides a contactless and nondestructive and high spatial resolution method for screening of banknotes, compared with the conventional THz imaging system.