See-trough Register Images in accurate front-to-back register. Designs or partial motifs seemingly printed at random on the front and back of the substrate, but which match up perfectly or form a complete motif when viewed by transmitted light. Imperfect register in counterfeits will produce a blurred image when viewed by transmitted light.
Anti Scan / Anti Copy Pattern Printed security features integrated in the background printing to protect against simulation through copying. The printed images and patterns contain embedded (hidden) information that is invisible to the naked eye under normal inspection conditions but becomes visible or legible, or causes flaws (mistakes) to appear after copying or reproduction with a scanner. Example: Orientation- and angle-modulated fine-line structures (SAM = Screen Angle Modulation)
Photochromic Ink Photochromic inks change their colour when exposed to UV light. When the UV light source is removed, the colour change stays for a certain time before the colour reverts to its original state. Examples: Estonia: passport, Malta: passport (since November 2000).