A Parallel Optical Image Security System with Cascaded Phase-only Masks

In many previous works, a cascaded phase-only mask (or phase-only hologram) architecture is designed for optical image encryption and watermarking. However, one such system usually cannot process multiple pairs of host images and hidden images in parallel. In our proposed scheme, multiple host images can be simultaneously input to the system and each corresponding output hidden image will be displayed in a non-overlap sub-region in the output imaging plane. Each input host image undergoes a different optical transform in an independent channel within the same system. The multiple cascaded phase masks (up to 25 layers or even more) in the system can be effectively optimized by a wavefront matching algorithm.