Hologram: optically variable image that is created through the interference of two laser beams. Holograms are the most common type of diffractive optically variable device (or DOVID – see above) and the term hologram is frequently used as a generic one in place of DOVID – not only because it is easier to pronounce but because the effects of holograms are similar to those of images created by the other, non-interference based, techniques.


Infra red (IR): that part of the electromagnetic spectrum that lies immediately beyond red light and therefore invisible to the naked eye.

Intaglio printing: the area of the image to be printed is recessed into the surface of the printing plate via engraving or etching and the recessed areas filled with ink. This area is filled with high viscosity inks, the excess is wiped from the plates and heavy pressure is applied to transfer the ink to the paper. The resulting raised ink profile gives intaglio-printed documents their characteristic tactility.

Intellectual Property (IP): property (as an idea, invention, or process) that derives from the work of the mind or intellect; also : an application, right, or registration relating to this. Common types of intellectual property include copyrights, trademarks, patents, industrial design rights and trade secrets in some jurisdictions.

Iridescent: the ability of some materials to create rainbow effects when they reflect white light .Pearls, oil films on water and bubbles all show iridescence. The effect can be created with foils and inks to create optically variable devices.

Isotope: one or more atoms with the same atomic number but a different number of neutrons


Level 1, 2 and 3 security features: a commonly-used means of grading security features.

Lock and key: a system of encryption whereby something (the ‘key’) is required to decode the message. The ‘key’ is usually a handheld device which renders meaningful that which was previously unintelligible. Possession of the key is restricted to certain individuals thereby limiting access to the encrypted information.

Luminescence: a collective term for the effects of color change or other visible characteristics under different sources of illumination

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