A method of indicating the condition of an item comprises illuminating the item to excite one or more photoluminescent markers incorporated within the item. Photoluminescent emission from the markers in response to the excitation is compared to one or more pre-defined photoluminescent signatures indicating different conditions of the item.
|Patent number||US 7,378,675 B2|
|Publication status||Published - 27 May 2008|
Ross, G. A., Johnson, G. I., Clark, B., & Forrest, S. J. (2008). Security markers for indicating condition of an item. (Patent No. US 7,378,675 B2). USPTO (United States Patent and Trademark Office). https://patentimages.storage.googleapis.com/b3/bd/1b/ff2e5d4504382a/US7378675.pdf