Media validation

A method of validating selected properties of media, the method comprising the steps of:

• (a) providing a sensor apparatus comprising a plurality of distinct monochromatic light sources and a light detector which is positioned to receive only diffusely reflected light from the sources;
• (b) locating an item of media in a path of the sensor apparatus;
• (c) activating a first monochromatic light source, and detecting light diffusely reflected from the media, to provide an output from the detector containing data relating to the response of the media to the light source;
• (d) moving the media with respect to the sensor apparatus;
• (e) activating another monochromatic light source, and detecting light diffusely reflected from the media, to provide an output from the detector containing data relating to the response of the media to the light source;
• (f) repeating steps (d) and (e) at least until each distinct monochromatic light source has been activated;
• (g) processing the sample data to determine a selected characteristic of the media;
• and
• (h) comparing the sample data against a reference database of data obtained from genuine media.

A system for sensing selected properties of media in a path, the system comprising:

• a number of monochromatic light sources for illuminating media in the path;
• a light detector for receiving only diffusely reflected light from media in the path;
• timing means for generating a timing signal;
• means for activating each light source in synchrony with the timing signal;
• means for recording outputs from the light detector;
• and
• means for processing the recorded outputs.