SYSTEM AND METHOD FOR ENCODING AND DECODING AN IMAGE OR DOCUMENT AND DOCUMENT ENCODED THEREBY

摘要

Holographic and diffractive security devices and documents carrying security devices as well as system, apparatus, and method for making and using security devices. Security devices provide at least one type of security feature in form of secret, hidden, or covert security feature, not visible to a normal unaided human eye. Covert security features may be any graphic or symbolic representation. One or multiple security features may be provided on any single security device in any combination. Covert feature is revealed either when a decoder device is used with the security device, or when the security device is oriented and viewed in predetermined manner. Embodiments may provide a second overt or non-covert security device in the form of a diffractive or holographic image or graphic that is visible to the unaided eye without use of any decoder or special viewing conditions.