| 摘要 |
An optical head (4) for sensing banknotes using six different groups of light sources, namely LEDs generating light at six different wavelengths both in the visible range of the spectrum and in the infra-red range of the spectrum. Unitary light guides (16,18) define the path between linear arrays (8,10) of the LEDs and the surface of a banknote (2). Diffusely reflected light is separately collected by a pin diode detector array (12). Both the LEDs and the detectors are commonly mounted on a single printed circuit board (14). The light sources (8,10) are arranged to shine directly into the light-receiving end of each light guide, which are unitary and allow the light to mix and spread within in order to provide a homogeneous illumination. The detectors (12) are optically isolated and detect discrete areas on the banknote transport path.
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