| 摘要 |
A coded hidden identification is provided for a selected printable item by providing a coded printing composition based on adding to and substantially uniformly mixing a selected number of populations of microparticles with a printing composition, said microparticles being normally invisible to the human eye and each such population having a group of microparticles of similar size, shape or color to form a combination of highly uniform and unique properties, the printing composition adapted for use in a printing machine, such as a photocopy or laser printing machine cartridge, and printing items with the coded printing composition so as to transfer the microparticles to the item. The microparticles may be characterized by a number of detectable properties, or a combination thereof, which are not detectable by the human eye to provide the coded hidden identification. The microparticles may contain, for example, a fluorescent dye and be made to fluoresce to reveal the identification, or they may be of a form such that magnification may be used to reveal the hidden identification.
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