| 摘要 |
<p>The authenticity of information on identity, authorisation and like documents is checked by covering the document with a coating containing a liquid crystal which luminesces for a short time after excitation by infrared light. The document is entered into the reader and passes an infrared source of the correct wavelength to excite the liquid crystals. An optical filter is placed between the document and the band pass detector which has an associated amplifier. The liquid crystal luminescence must be of the correct wavelength to be detected. A wide bandwidth detector of stray light provides a compensating input to the luminescence detector amplifier. If a document has been falsified the protective layer containing the liquid crystal will have been damaged and the break in the luminescence is detected as the document passes through the reader.</p> |
