An optical variable device or optically variable device (OVD) is an
iridescent
Iridescence (also known as goniochromism) is the phenomenon of certain surfaces that appear to gradually change color as the angle of view or the angle of illumination changes. Examples of iridescence include soap bubbles, feathers, butterfl ...
or non-iridescent security feature that exhibits different information, such as movement or colour changes, depending on the viewing and/or lighting conditions.
"More about Optically Variable Devices (OVDs)" ''Product Authentication & Security Directory''
/ref>photocopied
A photocopier (also called copier or copy machine, and formerly Xerox machine, the generic trademark) is a machine that makes copies of documents and other visual images onto paper or plastic film quickly and cheaply. Most modern photocopiers u ...
or scanned, nor can they be accurately replicated or reproduced. OVDs are often used as security devices and anti-counterfeiting
To counterfeit means to imitate something authentic, with the intent to steal, destroy, or replace the original, for use in illegal transactions, or otherwise to deceive individuals into believing that the fake is of equal or greater value tha ...
measures on banknotes, government-issued identification documents, or credit cards. OVDs can be created through a combination of printing
Printing is a process for mass reproducing text and images using a master form or template. The earliest non-paper products involving printing include cylinder seals and objects such as the Cyrus Cylinder and the Cylinders of Nabonidus. The ea ...
and embossing.
OVDs are based on diffractive optical structures. This gives cards the appearance of having different patterns, colours, and designs depending on the amount of light striking the OVD and the angle the OVD is viewed at. Holograms are a type of OVD.
References
Anti-counterfeiting
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