纯相位液晶空间光调制器拟合泽尼克像差性能分析

纯相位液晶空间光调制器作为波前校正器构成的高分辨率、低能耗、价格低廉、易于控制的自适应光学系统受到越来越多的关注.作为一种新型波前校正器件，它对波前像差的校正能力是反映其在自适应光学系统中应用的一个重要的指标，因此有必要仔细地研究它对各种像差的校正能力，以确定其可能的应用范围.波前校正器对各阶泽尼克像差的拟合效果有效地反映了该器件对不同像差的校正能力.利用256×256像素的纯相位液晶空间光调制器(LC-SLM)产生不同系数的前36项泽尼克像差分析LC-SLM对不同像差的校正能力.讨论了填充因子、离散像素     

纯相位液晶空间光调制器拟合泽尼克像差性能分析

纯相位液晶空间光调制器作为波前校正器构成的高分辨率、低能耗、价格低廉、易于控制的自适应光学系统受到越来越多的关注.作为一种新型波前校正器件,它对波前像差的校正能力是反映其在自适应光学系统中应用的一个重要的指标,因此有必要仔细地研究它对各种像差的校正能力,以确定其可能的应用范围.波前校正器对各阶泽尼克像差的拟合效果有效地反映了该器件对不同像差的校正能力.利用256×256像素的纯相位液晶空间光调制器(LC-SLM)产生不同系数的前36项泽尼克像差分析LC-SLM对不同像差的校正能力.讨论了填充因子、离散像素 关键词： 液晶空间光调制器 相位调制 自适应光学 泽尼克多项式     

纯相位液晶空间光调制器相位校正方法

利用泰曼-格林干涉系统,对纯相位液晶空间光调制器在808nm的相位调制特性进行了研究.为了提高其在大气湍流模拟时的仿真度,采用近似法和反插值法对相位调制曲线完成了线性校正,并对校正结果进行了对比分析.结果表明,虽然近似法校正简单易行,但经反插值法校正后,相位调制曲线的线性相关度更高,可达0.9916,校正误差更低,仅为0.06rad.通过对校正方法和误差来源的分析发现,反插值法还具有优化灵活的特点,能进一步改善校正效果,更具应用价值.     

利用纯相位型液晶空间光调制器实现空心光束

为了提高激光系统的整体效率,需要将出射光强整形为空心分布。采用纯相位型液晶空间光调制器整形近高斯分布光强到空心分布。基于能量守恒定律和等光程原理,分析了纯相位型液晶空间光调制器光束整形系统,得出了整形系统所需的相位分布。采用衍射光学方法,数值模拟了整形效果,讨论了入射光束束腰半径和强度分布等因素对整形效果的影响。利用纯相位型液晶空间光调制器实验实现了空心光束,实验测得的转换效率大于99%。     

基于液晶纯相位光调制器的4f系统去噪方法

分析了4f系统的噪声来源,提出使用液晶空间光调制器实时去除系统噪声.通过使用Zemike多项式拟合透镜等光学器件引入的像差,根据液晶纯相位光调制器利用位相共轭波进行静态波面校正的工作原理,提出了一种新的相位校正算法,模拟仿真美国BNS公司反射式256×256纯相位液晶空间光调制器,通过重构并逼近畸变波面,产生相位共轭波...     

利用纯相位型液晶空间光调制器实现空心光束

为了提高激光系统的整体效率,需要将出射光强整形为空心分布。采用纯相位型液晶空间光调制器整形近高斯分布光强到空心分布。基于能量守恒定律和等光程原理,分析了纯相位型液晶空间光调制器光束整形系统,得出了整形系统所需的相位分布。采用衍射光学方法,数值模拟了整形效果,讨论了入射光束束腰半径和强度分布等因素对整形效果的影响。利用纯相位型液晶空间光调制器实验实现了空心光束,实验测得的转换效率大于99%。     

纯相位空间光调制器实现振幅调制的技术研究

纯相位空间光调制器能够方便地模拟各种相位型光学元件,但不能直接模拟振幅型元件。使用两种方法,即棋盘相格法和闪耀光栅法,把由这两种方法生成的计算全息图加载到纯相位空间光调制器上,通过搭建的光束变换系统进行实验验证。实验结果表明,棋盘相格法和闪耀光栅法都能很好地实现振幅调制,用闪耀光栅法生成的叉状振幅光栅,给拉盖尔-高斯光束的合束带来了一种新的方法。     

基于液晶空间光调制器的光束变换研究

搭建了基于液晶空间光调制器的光束变换光路系统,介绍了一种通过编写程序来实现特定的光束强度分布的方法。利用MATLAB编写了闪耀光栅、菲涅尔透镜、环聚焦透镜、柱面菲涅尔透镜、小孔以及衍射调制板的灰度光栅图,并将其加载于液晶空间光调制器上,成功实现了光束变换。     

液晶空间光调制器在自适应光学中的应用

本文主要包括两方面的内容,一方面描述用液晶光阀产生空间与时间性能可控的小尺寸薄相位屏;另一方面则讨论用液晶空间光调制器实现波前相位畸变校正的可能性。从而表明,这类价格低廉、结构简单而性能可靠的非线性光学器件可望在高性能新型自适应光学系统中得到广泛应用。     

液晶空间光调制器相位调制的色散特性研究

提出用椭偏仪法测试了自制液晶空间光调制器(LCSLM)的相位调制色散特性.椭偏仪法具有光路简单,结果准确,测试自动化等优点,相比单色光源干涉仪测量方法更加简单实用.结果表明,在短波长(450 nm)处,LCSLM的相位调制能力为1.54λ(λ=450 nm),在长波长(800 nm)处,LCSLM的相位调制能力为0.70λ(λ=800 nm),与理论分析的色散特性基本一致.     

位相可控液晶空间光调制器的研究

论述了平行排列液晶的位相调制理论，进行了理论结果的计算模拟．研制出平行取向TFT型液晶空间光调制器并分析了其位相调制特性.结果表明,此平行取向的液晶空间光调制器可用于位相调制，其调整量优于0.7 μm，最小调整步长是0.052 μm．在ZYGO干涉仪上进行的位相控制实验，得到了很好的实验结果．     

Phase Modulation Characteristics Analysis of Optically-Addressed Parallel-Aligned Nematic Liquid Crystal Phase-Only Spatial Light Modulator Combined with a Liquid Crystal Display

An optically addressed parallel-aligned nematic-liquid-crystal spatial light modulator (PAL-SLM) has been studied as a dynamic phase-only light modulation device. The phase modulation characteristics of the PAL-SLM using a liquid crystal display (LCD) as an addressing mask were investigated by analyzing diffraction efficiencies resulting from binary gratings projected from the LCD. A more than 2π phase-only modulation depth was achieved. The highest first-order diffraction efficiency of approximately 38% was also obtained; this is close to the theoretical limit. The experimental results of diffraction efficiencies depending on the phase modulation depth are in good agreement with the simulation for the system operation.     

在粗糙表面上用液晶空间光调制器进行振动测量

为实现在一段时间内连续实时观测振动物体的全息干涉图形,采用覆盖铝箔的喇叭作为振动物体,利用铝箔原有未经特殊处理表面反射的漫反射光成像,并用光寻址液晶空间光调制器(Liquid crystal-sparial lightmodulator,LC-SLM)作为全息记录载体,来实现振动测量。实验中采用时间平均干涉测量法,得到了不同振动频率下物体的干涉图形。同时在连续改变振动物体的振动频率时,可以清晰地观察到物体振动全息干涉图形的变化过程,即近实时的全息干涉图形。     

高分辨率开环液晶自适应光学视网膜成像系统

利用液晶空间光调制器和夏克-哈特曼波前探测器作为核心器件搭建了一套开环双光源液晶自适应光学视网膜成像系统。系统采用人眼屈光0D基准设计并使用动态视标定位人眼,提高了人眼在测试时的稳定性,有效降低了由不同人眼个体差异带来的影响。通过补偿镜预补偿,配合微调照明光焦面,使照明光聚焦在眼底视觉细胞层,保证了像差探测精度和成像质量。利用人眼的偏振特性,采用偏振光照明的方式,将系统的能量利用率提高了20%。优化了系统的工作流程,优化后系统连续工作频率可超过20Hz。对4名志愿者进行了实验,均获得了清晰的眼底视网膜细胞图像。     

采用液晶空间光调制器进行激光光束的空间整形

提出采用液晶空间光调制器进行激光束的实时,可调控光束空间整形的新方法,研究了液晶空间光调制器的光学调制特性,用液晶空间光调制器衬时产生的软边切趾光阑与空间滤波器结合,有效地对任意光束进行空间整形,获得光束填充因子高,近“平顶”光强的光束近场分布。     

Grayscale-Memory Spatial Light Modulator with Polymer-Dispersed Phase-Transition Liquid Crystal

A new storage-type spatial light modulator has been developed which uses a polymer-dispersed phase-transition liquid crystal film and a photoconductor for high-brightness projection displays. The liquid crystal film containing micrometer-sized chiral nematic liquid crystal domains subdivided by a unique honeycomb polymer network functions as a memory layer for an input image. The liquid crystal domains independently maintain the binary alignment states in the opaque (light-scattering) cholesteric phase or transparent nematic phase. Grayscale images can be displayed according to the spatial distribution of the bistable liquid crystal domains. The device exhibits rapid response of a few ms and a limiting resolution of 32 lp/mm. It has the advantages of high transmittance without polarizers and ease of fabrication due to the free-standing liquid crystal film.     

High Efficiency Electrically-Addressable Phase-Only Spatial Light Modulator

To realize a high efficiency electrically addressable phase-only modulator, we have coupled a liquid crystal display (LCD) to an optically addressed parallel-aligned nematic liquid crystal spatial light modulator (PAL-SLM) with a set of lenses. Phase modulation exceeding 3ϖ at 532 nm wavelength was obtained. We obtained linear transfer characteristics for phase modulation at various desired phase levels after calibration and adjustment of the transfer characteristics of the PAL-SLM and the LCD. Diffraction efficiency of 40% for binary phase grating and of 90% for 8-level blazed phase grating, which were very close to the simulation values, were observed. The power loss of the readout light was caused when passed through a half mirror, therefore, we examined a setup using an oblique readout light at the modulator. Very high diffraction efficiency was obtained from the setup by optimizing the polarization direction and optical path for this light, and the orientation of liquid crystals. Since the modulator can perform at better than 90% diffraction efficiency and at nearly 100% reflectivity, various high efficiency systems utilizing such modulators are expected.     

Neural Network Control of Liquid Crystal Spatial Light Modulator for Spectral Synthesis of Light

If illuminating light with expected spectral distribution can be synthesized, it will be a great help in many-applications, such as computer vision, pattern recognition, industrial quality control, and remote sensing. A light source system containing a liquid crystal spatial light modultor (LCSLM) is proposed for this purpose. A supervised neural network with a single layer was used to control the system. After training the neural nrtwork with data acquired from the system, it gives the data which should be written to LCSLM in order to synthesize illuminating light having certain spectral distribution. Eight spectral distributions were synthesized to test the performance of the system, and the average synthesizing error was 12%.     

Spatial Temporal Analysis of Electrically-Addressable Phase-Only Spatial Light Modulator

An optically addressed parallel-aligned nematic-liquid-crystal spatial light modulator (PAL-SLM) has been studied as a dynamic phase-only modulation device. A computer control feature of the spatial light modulator is strongly desired for practical applications. For those demands, an electrically-addressable phase-only spatial light modulator has been developed to combine a liquid crystal display (LCD) with a PAL-SLM (LCD-coupled PAL-SLM) and its performance has been reported. However, a temporal characteristic especially two-dimensional (2D) response has not been discussed before. In this paper, 2D response analysis system has been constructed by using a high-speed complementary Metal-Oxide-Semiconductor (CMOS) camera (1000 frames/sec) and the 2D-modulation characteristic of the LCD-coupled PAL-SLM has been observed. As a result, the LCD has a spatially non-uniform modulation characteristic due to a scanning addressing. It has the potential to cause problems in high speed switching for a computer generated hologram. On the other hand, the spatial non-uniformity has not been observed with the LCD-coupled PAL-SLM.