Binary phase image encryption method

We have developed a binary phase-only encryption technique based on a phase-coding method which uses a generalization of the Zernike phase contrast technique, that breaks the small-phase-angle limitation of Zernike´s method. We have already demonstrated this phase-coding technique for lossless image formation experimentally and in this paper we describe the extension of this to optical encryption. Our phase only encryption approach is simpler than the more conventional combined amplitude and phase approach which requires the double phase scrambling on an amplitude mask. We demonstrate how this binary phase encryption architecture can be realised in practice through the use of a commercially available parallel-aligned liquid crystal spatial light modulator (PAL-SLM).