DID® Diffractive Identification Element
A diffractive optically variable image (developed by SURYS, France) which contains elements that change their color when rotating the image by 90° (the angle of observation is not changed). DID® is transparent at a right angle of observation that makes it easy to read personal data.
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Fig. 1. France. Passport issued in 2013:
a — data page. Paper substrate; b — the same. DID®. View at an angle of 45º in oblique light; c — the same. A color change observed while rotating the image by 90° without changing the angle of observation and illumination. Blue elements become green and vice versa
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Fig. 2. Slovakia. Passport issued in 2014:
a — data page. Polymer substrate; b — the same. DID®. View at an angle of 45º in oblique light; c — the same. A color change observed while rotating the image by 90° without changing the angle of observation and illumination. Green elements become orange and vice versa