Multitone reconstruction visual cryptography based on phase periodicity |
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Institution: | School of Information Science and Technology, North China University of Technology, Beijing 100144, China |
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Abstract: | The current no-computation grayscale image visual cryptography (VC) can only achieve halftone reconstruction but cannot truly achieve multitone. To solve this problem, we propose the concept of phase periodicity of the retarder film and calculate the optical axis angle set with phase periodicity. According to the phase periodicity, we propose a retarder film phase periodicity visual cryptography (RPP-VC). In RPP-VC, the secret pixels are encoded as the optical axis angles of retarder films and distributed to shares. The decoding process does not require computation. The reconstructed image has no pixel expansion and can reach up to 23 tones. The quality of the reconstructed images has been greatly improved and the evaluation indicators of perceived quality are nearly doubled compared with other grayscale image VC schemes. The experimental results verify the feasibility of RPP-VC. |
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Keywords: | Grayscale image Visual cryptography Phase periodicity Light polarization |
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