There are provided a watermark information embedding device and a watermark information detection device which can correctly extract classified information. In the watermark information embedding device, a plurality of dot patterns the wave directions and/or wavelengths of which are changed depending...http://www.google.com.tw/patents/US7085399?utm_source=gb-gplus-share專利 US7085399 - Watermark information embedding device and watermark information detection device
