| 摘要 |
For identification and authentication purposes, especially in the retail trade, articles 1 or their packaging, are labelled with a mark 2 which is only discernible as such with the aid of suitable infrared imaging equipment. As described the mark 2 comprises a combination of carbon black ink visible under normal and infrared illumination, and dye based black ink which is transparent to infrared. The mark is illuminated by a tungsten lamp 6 with a filter 7 blocking visible light, and is read by a CCD television camera 3 with an optical filter 5. <IMAGE> |
