Multi-image optical encryption method of JTC system combining CGH and frequency shift

In order to improve the practicability of JTC optical image encryption system, solve its noise problem, improve its encryption efficiency and security, a multi-image optical encryption method based on computer generated hologram (CGH) and the frequency shift of Fourier transform was proposed. Firstly, each image with different size and type was modulated by random phase and Fourier transform, then the frequency spectrum of multiple images was modulated by frequency-shift phase and superimposed to be encoded into binary real-value CGH, finally the CGH was encrypted into joint power spectrum by JTC optical image encryption system. In the decryption process, the encrypted image was decrypted by 4F system to obtain the CGH. The binary real-value CGH has strong noise resistance to eliminate the effects of noise. Then, multiple decrypted images can be obtained after Fourier transform. Simulation results show that the proposed method can encrypt and decrypt multiple images of different sizes and types in parallel, and has high encryption efficiency. Meanwhile, multiple images with mutual keys and double optical keys ensure the security of the encryption system.