Optical Image Encryption With Divergent Illumination and Asymmetric Keys
Xiaogang Wang, Guoquan Zhou, Chao‐Qing Dai, Junlang Chen · IEEE photonics journal · 2017
A flexible optical encryption system based on divergent illumination and asymmetric encoding is proposed. The input image is encrypted by use of two random phase masks (RPMs) located at the input and the conjugate plane in a diverging spherical wave field. Compared with the counterparts using planar illumination and symmetric keys, a significant difference is that continuous change of positions of optical elements applied for encryption is allowed, resulting in decryption keys that are different from the encryption keys (or their conjugates) and variable size display of encrypted/decrypted images. A detailed mathematical description and calculation results with different bandwidths of the system support our proposal.