Parallel processing and scheduling techniques applied to the quality control of bill sheets

Automatic quality control examination of banknotes constitutes an important research challenge for the main printing organizations in the world. It is worth to note that presently there is no commercial product with an acceptable performance, in spite of the efforts spent during last ten years. The product complexity lies in the combination of several printings with the purpose of achieving hard to counterfeit banknotes. The printing system that is necessary for banknotes manufacturing, causes significant differences between several printed sheets in similar conditions. However, in spite of these differences, while respecting certain tolerances, the banknotes are accepted. The required quality of the product demands an exhaustive inspection of the bill sheets. Nowadays the quality control is carried out by manual turn over of the bill sheet, reaching a speed of 400 sheets/hour. It has been developed a system that works out an automatic inspection at a rate of 3600 sheets/hour.