 thumb|150px|the eurion constellation is made up of five rings. the eurion constellation is a pattern of symbols incorporated into a number of banknote designs worldwide since about 1996. it is added to help imaging software detect the presence of a banknote in a digital image. such software can then block the user from reproducing banknotes to prevent counterfeiting using colour photocopiers. research shows that the eurion constellation is used for color photocopiers and is likely not used for computer software. == description == the name "eurion constellation" was coined by markus kuhn, who uncovered the pattern in early 2002 while experimenting with a xerox colour photocopier that refused to reproduce banknotes.markus kuhn: the eurion constellation. security group presentation, computer laboratory, university of cambridge, 8 february 2002. the word is a portmanteau of eur, the euro's iso 4217 designation, and orion, a constellation of similar shape. the eurion constellation first described by kuhn consists of a pattern of five small yellow, green or orange circles, which is repeated across areas of the banknote at different orientations. the mere presence of five of these circles on a page is sufficient for some colour photocopiers to refuse processing. andrew steer later noted simple integer ratios between the squared distances of nearby circles, which gives further clues as to how the pattern is meant to be detected efficiently by image-processing software. the eurion constellation is most prominent, and was therefore first recognised, on the 10 euro (â¬10) banknote. some banks integrate the constellation tightly with the remaining design of the note. on 50 dm german banknotes, the eurion circles formed the innermost circles in a background pattern of fine concentric circles. on the front of former bank of england elgar Â£20 notes, they appear as green heads of musical notes, however on the smith Â£20 notes of 2007 the circles merely cluster around the 'Â£20' text. on some u.s. bills, they appear as the digit zero in small, yellow numbers matching the value of the note. on japanese yen, these circles sometimes appear as flowers. technical details regarding the eurion constellation are kept secret by its inven
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