The working principle of fluorescence detection is to detect the paper quality of RMB. The renminbi is made of special paper (containing more than 85% of high-quality cotton). Counterfeit banknotes are usually made of bleached plain paper. The bleached paper will show fluorescence under ultraviolet light (blue light with a wavelength of 365nm). The reaction (blue light with a wavelength of 420-460nm is diffracted under the excitation of ultraviolet rays), the RMB has no fluorescence reaction. Therefore, by irradiating the moving banknote with an ultraviolet light source and simultaneously detecting the fluorescence reflection of the banknote with a silicon photocell, the authenticity of the banknote can be determined. In order to eliminate the interference of ambient light on the identification of counterfeit, it is necessary to install a set of color filters with the same transmission wavelength as the fluorescence reaction wavelength of the counterfeit banknote on the surface of the silicon photocell.
A. In fluorescence detection, two issues need to be paid attention to:
1. Detect the shading of the space. Outside light entering the detection space will cause false alarms;
2. Dustproof of UV light source and photocell. There is a large amount of dust in the process of counting money, and the dust adhering to the surface of the light source will weaken the detection signal and cause false negatives.
B. For the fifth edition of RMB, fluorescent characters can be detected at the same time (printed with colorless fluorescent ink, detected by another silicon photocell, the transmission wavelength of the color filter is the same as the fluorescence reaction wavelength of the real banknote) to improve the effect of forgery.