Visual Cryptography Using Polarization-Modulation Films

Conventional visual cryptography reduces the resolution of secret information because its encryption is based on spatial coding that requires multiple subpixels to modulate light intensity. To overcome this resolution problem in visual cryptography, we propose a new type of visual cryptography based on polarization processing. Each pixel in a secret image is encrypted into a corresponding single pixel in encrypted films. The encrypted films are composed of a polarizing film and patterned retarder films. We developed an encryption code set for decoding by stacking the encrypted films in the correct order. Furthermore, we demonstrated multiple decoded results with encrypted films that exhibit stacking order dependence.