A Low-Cost Multi-Camera System With Multi-Spectral Illumination

Certain characteristics of prints are invisible for the naked eye, e. g. elements printed at small print sizes or reflection/absorption characteristics of print inks, which are typical for security prints such as banknotes. Detailed inspections of these characteristics are usually carried out using special and expensive equipment. Often image acquisition and processing are carried out on different systems. This contribution proposes a compact and modular standalone multi-camera image processing system with multi-spectral illumination for such document inspection applications. It describes its standard off-the-shelf components, their designs, dependencies, and links between them. The system allows to acquire planar test objects at various optical resolutions and process the images internally using standard software or application-specific algorithms, executed on the integrated processing platform. The functionality of a demonstration device is shown in the scope of a banknote authentication application based on print method detection with implementations of the Sound of Intaglio and Sound of Offset algorithms. The benefits of multi-spectral illumination are demonstrated in additional banknote tests.