Optical image encryption via ptychography.

Ptychography is combined with optical image encryption for the first time. Due to the nature of ptychography, not only is the interferometric optical setup that is usually adopted not required any more, but also the encryption for a complex-valued image is achievable. Considering that the probes overlapping with each other is the crucial factor in ptychography, their complex-amplitude functions can serve as a kind of secret keys that lead to the enlarged key space and the enhanced system security. Further, since only introducing the probes into the input of common system is required, it is convenient to combine ptychography with many existing optical image encryption systems for varied security applications.