Optical authentication

A method for determining a signature from an article in a reading volume, the method comprising:

• generating a coherent beam;
• directing the coherent beam into the reading volume;
• collecting signals created by scatter of the coherent beam within the reading volume, wherein different ones of the signals relate to scatter from different parts of the reading volume, using a detector arrangement having a numerical aperture greater than a predetermined minimum;
• and
• determining a signature for an article in the reading volume from the collected signals.

An system for verifying the authenticity of an article, the system comprising:

• determining a signature from an article using an apparatus operable to direct a coherent beam into a reading volume where the article is arranged, operable to collect signals created by scatter of the coherent beam within the reading volume, wherein different ones of the signals relate to scatter from different parts of the reading volume, the detector arrangement having a numerical aperture greater than a predetermined minimum, and operable to determine a signature for an article in the reading volume from the collected signals;
• storing the signature so determined in a database;
• determining a signature from an article using an apparatus operable to direct a coherent beam into a reading volume where the article is arranged, operable to collect signals created by scatter of the coherent beam within the reading volume, wherein different ones of the signals relate to scatter from different parts of the reading volume, the detector arrangement having a numerical aperture greater than a predetermined minimum, and operable to determine a signature for an article in the reading volume from the collected signals;
• and
• comparing the signature so generated to the signature stored in the database to determine whether the same article was the source of both signatures.