A multi-wavelength light source for use in a banknote validator comprises a housing containing a plurality of LEDs and a window for releasing light emitted by the LEDs. Visible wavelengths have a direct path to a diffuser located in the window. Infra-red wavelengths have to be diffusively reflected by...http://www.google.de/patents/US6991347?utm_source=gb-gplus-sharePatent US6991347 - Currency acceptor, and light source for use therein
