Han-Yen TU, Mao-Ling CHEN¹ and Chau-Jern CHENG¹

Department of Electronic Engineering, St. John's University, Taipei 25135, Taiwan, R.O.C.
¹Department of Electro-Optical Engineering, National Taipei University of Technology, Taipei 10608, Taiwan, R.O.C.

(Received February 24, 2006; Accepted May 11, 2006)

This work proposes and demonstrates the feasibility of gray image encryption using multiple polarization encoding, in which the cascaded twisted nematic liquid crystal devices sandwiched between a crossed polarizer pair are used to implement exclusive OR (XOR) logical encryption and decryption. The polarization encoding scheme provides a multi-channel XOR logic operation to secure bit-plane images derived from a gray image, according to the adiabatic following properties of twisted nematic liquid crystal devices. Experimental data reveal that the multiple polarization encoding schemes for gray image encryption and decryption are performed with acceptable image quality by selecting appropriate polarization orientation and modulation conditions. Both analytic and experimental results are presented and discussed.

Key words: polarization-encoding, optical encryption, exclusive OR logic