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中国物理学会期刊

面向纯相位型全息显示的自适应混合约束迭代算法

CSTR: 32037.14.aps.72.20221690

Adaptive mixed-constraint Gerchberg-Saxton algorithm for phase-only holographic display

CSTR: 32037.14.aps.72.20221690
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  • 纯相位型计算全息图舍弃全息面上的振幅信息, 降低了全息显示的图像质量. 迭代法通过多次正、逆向的波前传播计算, 优化了纯相位型计算全息图的相位轮廓, 提升了全息再现的图像质量. 然而, 传统迭代法可能存在迭代发散、收敛速度偏慢以及再现质量受限等问题. 本文提出了一种基于角谱传播模型的自适应混合约束迭代算法, 通过在迭代中加入自适应的反馈机制和频带约束策略, 增加了迭代优化的自由度, 提升了迭代的收敛性和全息再现的图像质量. 仿真和实验结果表明, 提出的算法能够在较短的计算时间内获得更高重建质量的纯相位型计算全息图, 对于高质量的全息显示具有重要应用价值.

     

    At present, spatial light modulators are incapable of modulating both the amplitude and phase of the wavefront simultaneously. Therefore, when a spatial light modulator is used for holographic display, it is necessary to encode the complex amplitude of the object wave into amplitude-only or phase-only computer-generated-hologram. The phase-only holographic display has attracted much attention of researchers due to its characteristics of high diffraction efficiency and no conjugate image. However, current optimization algorithms for generating phase-only hologram have the problems of iterative divergence, slow convergence speed, and poor reconstruction quality, which is difficult to satisfy the requirements for high-quality holographic display. In this work, we propose an accurate adaptive mixed constraint Gerchberg-Saxton algorithm by constraining the frequency bandwidth in the hologram plane and adaptively constraining the amplitude of the reconstructed image in the image plane based on the angular spectrum propagation theory. Firstly, we use the angular spectrum propagation model without paraxial approximation to simulate the forward and backward propagation of the light wave for ensuring the accuracy of the wavefront propagation. Secondly, dividing the image plane into signal area and noise area according to the spatial distribution of target image, and different adaptive feedback strategies are set up for the two regions based on the optimized effect of the phase-only hologram. The adaptive feedback strategy is established, which can accelerate the convergence speed of the proposed algorithm and enhance the hologram of freedom of the optimization. Finally, the frequency bandwidth constraint strategy is introduced in the hologram plane to optimize the edge pixels and compensate for the frequency information loss of the phase-only computer-generated hologram, which improves the reconstruction quality of the hologram. After 100 iterations, the average correlation coefficient of the holographic reconstructed image of the proposed algorithm is about 0.9857, and the average peak signal-to-noise ratio is about 31.02 dB. The correlation coefficient and the peak signal-to-noise ratio of the reconstructed images of the proposed algorithm are better than those of the Gerchberg-Saxton algorithm with only frequency bandwidth constraint strategy, and the proposed algorithm has clearer texture and better display effect. The results of numerical simulations and optical experiments show the feasibility and effectiveness of the proposed method. The proposed adaptive mixed constraint Gerchberg-Saxton algorithm is a promising technology for high-quality holographic display.

     

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