Phase-only holograms (POHs) are often generated by the Gerchberg–Saxton (GS) algorithm. Nevertheless, low-quality reconstruction and iterative divergence plague the traditional GS method, reducing the quality of holographic display. Noise still affects adaptive weighted GS (AWGS) algorithms, despite their ability to ensure convergence through the addition of planned feedback. We propose an optimized AWGS algorithm, named optimized adaptive weighting constraints (OAWGS), for the generation of POHs for high-quality holographic display. The contrast and intensity of the signal domain are enhanced by adding a weighting factor to the AWGS feedback. By introducing non-signal regions and applying an optimized random phase as the initial phase, the OAWGS algorithm substantially improves the quality of holographic reconstruction. Compared with the AWGS algorithm, the proposed method can improve the peak signal-to-noise ratio by 5.45 dB and converge. It could reach convergence after 20 iterations. Both simulation and experiment results verify the effectiveness of the proposed method.
A multiple-image encryption method based on a computer-generated phase-only hologram (POH) algorithm and chaotic systems is proposed. In the proposed method, first, a modified Gerchberg–Saxton (GS) algorithm is applied to transform the multiple-image into corresponding sub-sampled POHs. Then, the multiple POHs are combined using spatial division multiplexing (SDM). The combined hologram is then mapped into a digital image, and each pixel of the digital image is transformed by a chaotic system to improve security and form the final ciphertext. The modified GS algorithm is employed to generate a sub-sampled POH, which is a prerequisite for SDM. The adoption of SDM eliminates issues such as information leakage due to inter-image crosstalk and ensures the quality of decrypted images. The transformation based on a chaotic system leads to nonlinearity and unpredictability in the encryption process, which further increases the complexity of the encryption system. Numerical simulation demonstrates the security and feasibility of the proposed multiple-image encryption method.
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