Recognition is to distinguish between true and false by detecting the inherent characteristics of the renminbi. The banknote counter is a mechatronic product, involving knowledge in many fields such as mechanics, electricity, optics, magnetism, etc., and requires mutual cooperation in all aspects.
Fluorescence detection
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 ordinary paper. The bleached paper will fluoresce 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 judged. 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. External 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.
Magnetic detection
The working principle of magnetic detection is that some parts of the large denomination real banknotes (20, 50, 100 yuan) are printed with magnetic ink, and the magnetism of the moving banknotes is detected by a set of magnetic heads, and the magnetism is analyzed through the circuit, which can be distinguished The authenticity of the banknotes.
In magnetic detection, good friction between the magnetic head and the banknote is required. If the head is too high, the impact signal will be large, causing false alarms; if the head is too low, the signal will be weak, causing false alarms. The detection needs can be met by controlling the height of the magnetic head (guaranteed by processing and assembly) and installing a banknote pressing rubber wheel above the magnetic head.
The magnetic detection methods of RMB can be divided into four types:
⑴Check whether there is magnetism. Most banknote counters on the market use this method. Because of the ease of manufacture, the detection rate of counterfeit banknotes in this method is low.
⑵ What to do to detect magnetism according to the magnetic distribution. Two or three sets of magnetic heads are used to detect magnetism in a branch, and the level of forgery identification can be raised to a level. Some currency counters on the market use this method.
⑶ Detect the magnetic properties of the fifth edition of the RMB metal wire. The current level stays at detecting the presence or absence of magnetism. According to our observations on the oscilloscope, the magnetism of the metal wire is a very regular rectangular wave, and the magnitude is also very accurate. Because it is difficult to imitate, if this feature can be used in magnetic detection, it will greatly improve the level of forgery.
⑷ Detect the magnetism of the fifth edition RMB horizontal code. The current level stays at detecting the presence or absence of magnetism. Because the horizontal number is a set of numbers with certain magnetism, if the number and size of the magnetism of the horizontal number are detected, the level of forgery can be greatly improved.
Infrared penetration detection
The working principle of infrared penetration is to use RMB paper which is stronger and denser and the ink thickness printed with gravure printing technology is higher, so the infrared signal absorption ability is stronger to distinguish the authenticity of banknotes. There is a certain difference between the paper characteristics of RMB and counterfeit banknotes. When infrared signals are used for penetration detection of banknotes, their ability to absorb infrared signals will be different. Using this principle, counterfeit identification can be achieved. It should be noted that the color and thickness of the ink will also cause differences in infrared penetration. Therefore, it is necessary to perform mathematical operations and comparative analysis on the signals of infrared penetration detection
