基于参数空间遍历的空间光调制器量化取值优化  

Optimization of Quantization Value for Spatial Light Modulators Based on Parameter Space Traversal

作　　者：何泽浩 隋晓萌 曹良才[1] 金国藩[1] He Zehao;Sui Xiaomeng;Cao Liangcai;Jin Guofan(State Key Laboratory of Precision Measurement Technology and Instrument,Department of Precision Instruments,Tsinghua University,Beijing 100084,China)

机构地区：[1]精密测试技术及仪器国家重点实验室,清华大学精密仪器系,北京100084

出　　处：《中国激光》2021年第12期307-316,共10页Chinese Journal of Lasers

基　　金：国家自然科学基金(62035003,61775117);清华大学自主科研计划(20193080075)。

摘　　要：由于现有空间光调制器(SLM)的调制特性,连续取值的复振幅型计算全息图(CGH)通常需要被转换为离散取值的纯振幅型或纯相位型CGH。将连续值近似为离散值的量化过程会对CGH的全息重建质量产生显著的影响。选择峰值信噪比(PSNR)作为重建质量的评价依据,采用参数空间遍历法,定量评估了CGH振幅和相位的量化取值对重建质量的影响。评估过程充分考虑了分辨率、补零范围、重建距离、重建波长、随机相位、像素间距、位深度及相位调制偏差等关键参数对全息重建的作用。在此基础上,提出了针对现有和未来SLM的最佳量化方案。Objective Obtaining high-quality reconstruction is desirable in computer-generated holography.Continuous complex-amplitude computer-generated holograms(CGHs)can present the most enhanced reconstruction quality because accurate amplitude and phase values rather than approximate values are obtained.However,in a practical system,CGHs need to be uploaded on the spatial light modulator(SLM).The most commonly used SLMs can only modulate either amplitude or phase.In addition,SLMs generally have pixelated structures with limited value ranges.It is necessary to sample the continuous distribution into a two-dimensional matrix with specific resolution and discrete pixel values in practical applications.This characteristic may harm the holographic reconstruction quality.Therefore,an optimization method based on parameter space traversal is proposed in this study to evaluate the effect of quantization on the holographic reconstruction quality.Various related parameters are considered in the evaluation.Proper quantization in some specific applications is also suggested.Methods The CGH of a target object is calculated using the angular-spectrum model.In this model,when the reconstruction distance is too large,an aliasing error in the transfer function will be introduced.The maximum reconstruction distance,also called the effective distance,is determined by the Shannon-Nyquist sampling theorem.Meanwhile,when the reconstruction distance is too small,different diffraction orders on the reconstruction plane will interfere with each other.The minimum reconstruction distance is determined by the grating function.To quantitatively evaluate the reconstruction quality,the peak signal-to-noise ratio(PSNR)is used as the index to measure the difference between the reconstructed and target objects.Moreover,a traversal method is used to quantitatively evaluate the influence of quantization.Considering the pixelated structure and discrete value ranges of current SLMs,the continuous complex-amplitude distribution is converted into quantized am

关 键 词：全息 计算全息 全息显示 振幅 相位 量化 

分 类 号：O436[机械工程—光学工程]