Visual Cryptography Using Interference Color of High-Order Retarder Films
Kenji Harada, Takenobu Yamaguchi, Tomohiro Tsuchida, Daisuke Sakai · Japanese Journal of Applied Physics · 2013
Visual cryptography is known as a method of sharing a secret image through several encrypted images. Conventional visual cryptography can display only monochrome images. We develop a multicolor visual encryption technique using the interference color of high-order retarder films. The encrypted films are composed of a polarizing film and retarder films. Retarder films exhibit an interference color upon sandwiching between two polarizing films. A prototype of a visual cryptography device using interference color is developed. Eight colors are represented by combining an encrypted image and a decoding mask composed of retarder films with various retardations.