A banknote identification module is a core component of a financial self-service device, and is configured to identify the denomination, authenticity and quality of a banknote in the process of a cash transaction. A core element of the banknote identification module is a CIS (contact image sensor). The banknote identification module collects multispectral signals of a banknote by the CIS, and performs denomination identification, authenticity identification and quality sorting of a banknote by using characteristics of multispectral imaging of the banknote. For a visible light signal of a previous generation of banknote identification modules, only a natural white light signal is used. While, for a visible light signal of a new generation of banknote identification modules, at least three optical signals are used, including a red light signal, a green light signal and a blue light signal, and level of color information can reach a level of true colors, which significantly improves the reliability and accuracy of banknote identification, in particular for some altered banknotes with a high counterfeit degree, as compared with the detection with the natural white light signal.
It can be seen from above that the accuracy of banknote identification is closely related to the performance of the CIS. However, due to a difference in the manufacturing process, not all of the factory-fresh CISs can be entirely the same and there are some differences more or less in the performance. In the existing banknote identification technology, multispectral signals are generally collected by a CIS, and color eigenvalues corresponding to the multispectral signals are extracted and transmitted to a banknote classifier for banknote classification processing.
However, since there is a difference in performance among the CISs, multispectral signals collected by different CISs for a same one banknote may also be different, which causes a difference in the finally obtained banknote classification result, thereby affecting the accuracy of banknote identification and resulting in a risk of mistaken identification.