EURion constellation
A number of new designs of banknotes contain a pattern known as the EURion constellation which can be used to detect their identity as banknotes to prevent counterfeiting using modern inexpensive digital scanners, colour printers, and image processing software. This feature prevents the user from scanning notes, or even printing. It was discovered after some users tried to scan euro banknotes in image editors such as Adobe Photoshop, or Paint Shop Pro.
The EURion constellation consists of a pattern of five small circles, which is repeated across areas of the banknote at different orientations.
The EURion constellation was first detected on the new Euro banknotes. It was then found to have been printed on (obsolete) Deutschmark notes as well.
The EURion constellation also appears on recent British banknotes, and the back of the new U.S. $20 bill.
