There are constellation patterns on the left side of the front and the right side of the back of the paper money, all of which are round and empty. The front is 24, red, the upper part of the back is 13, and the lower part is 16, orange. Once the color copier finds the paper money with this constellation pattern, it will cause serious color distortion in the output. This technology was invented by Omron Corporation of Japan, so these small circles are also called Omron rings.