10 January 2018 A novel automatic full-scale inspecting system for banknote printing plates
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Quality assurance of banknote printing plates is an important issue for the corporation which produces them. Every plate must be checked carefully and entirely before it's sent to the banknote printing factory. Previously the work is done by specific workers, usually with the help of powder and magnifiers, and often lasts for 3 to 4 hours for a 5*7 plate with the size of about 650*500 square millimeters. Now we have developed an automatic inspecting system to replace human work. The system mainly includes a stable platform, an electrical subsystem and an inspecting subsystem. A microscope held by the crossbeam can move around in the x-y-z space over the platform. A digital camera combined with the microscope captures gray digital images of the plate. The size of each digital image is 2672*4008, and each pixel corresponds to about 2.9*2.9 square microns area of the plate. The plate is inspected by each unit, and corresponding images are captured at the same relative position. Thousands of images are captured for one plate (for example, 4200 (120*5*7) for a 5*7 plate). The inspecting model images are generated from images of qualified plates, and then used to inspect indeterminate plates. The system costs about 64 minutes to inspect a plate, and identifies obvious defects.
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Jian Zhang, Jian Zhang, Li Feng, Li Feng, Jibing Lu, Jibing Lu, Qingwang Qin, Qingwang Qin, Liquan Liu, Liquan Liu, Huina Liu, Huina Liu, "A novel automatic full-scale inspecting system for banknote printing plates", Proc. SPIE 10616, 2017 International Conference on Optical Instruments and Technology: Optical Systems and Modern Optoelectronic Instruments, 1061606 (10 January 2018); doi: 10.1117/12.2295516; https://doi.org/10.1117/12.2295516


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