用于集成成像3D显示的曲面微透镜阵列设计与仿真

针对集成成像3D显示观看视场范围小的问题和微透镜之间间隙的杂散光干扰导致的显示质量下降问题,提出了适合柔性显示及曲面显示器的曲面针孔/微透镜阵列结构.采用TracePro光学仿真软件对基于曲面针孔/微透镜阵列的集成成像3D显示的记录和重构过程进行仿真,结果显示:在记录和重构阶段,曲面针孔/微透镜阵列可以有效地减少透镜阵列之间杂散光引起的图像质量变差的问题;当记录和重构阶段均用曲面/针孔微透镜阵列时,记录三维物体的视角大,获得重构图像的视场角也相对较高.采用旋转接收屏法获取不同观看视角下的图像质量,当曲面针孔/微透镜阵列的曲面度数为30°时,重构图像质量最好.     

用于曲面集成成像的微透镜数值孔径优化

针对目前集成成像3D显示系统存在视场角范围小以及重构图像分辨率低的问题,设计一种适用于曲面集成成像3D显示且具有不同数值孔径的柔性微透镜阵列结构,并成功搭建基于曲面屏的集成成像3D显示系统。采用Trace Pro光学仿真软件建立曲面集成成像3D显示系统模型,研究微透镜的数值孔径对曲面集成成像3D显示系统重构性能的影响规律。结果表明：当微透镜尺寸和厚度一定时,数值孔径越大,重构图像的质量越好,且视场角越大;当柔性微透镜阵列的数值孔径为0.376时,重构图像具有较高的分辨率,当视场角达到60°时,重构图像依然清晰。为了验证仿真,制备具有不同数值孔径的柔性微透镜阵列并搭建曲面集成成像系统样机,得到的实验结果与仿真结果基本一致。     

三维集成成像显示系统分辨率的测试模型设计

建立了三维集成成像显示系统的分辨率测试模型,对模型所采用的形状、比例和条纹宽度等进行设计研究.首先,根据集成成像技术多角度拍摄测试模型得到视差图;然后,根据二维分辨率测试卡的测试方法对视差图清晰度线进行标定;最后,计算视差图得到合成图像并显示到集成成像系统上,测试得到系统重构三维物体的分辨率.实验结果表明:该设计支持观察者测试不同角度、不同深度的显示分辨率,量化了集成成像显示系统分辨率.模型包含8级分辨率清晰度线,基本满足当前三维显示系统分辨率的测试范围,可用于测量集成成像显示系统的重构景深和视场角.     

基于视场拼接的全视差三维显示系统

提出了一种新的基于视场拼接的全视差三维显示方法及图像生成方案.系统核心部分由一个微投影机阵列、一个反射光路和一个散射屏组构成,图像生成方案采用基于OpenGL的算法实现.为了验证所提出的基于视场拼接理论的正确性,利用液晶显示器、菲涅耳镜组、定向散射屏和背投式反射光路搭建了实验样机.该装置可以在更紧凑的系统结构下显示包括横向视差和纵向视差在内的三维图像,并且通过图像生成算法的配合实现了动态三维显示效果.     

基于视场拼接的全视差三维显示系统

提出了一种新的基于视场拼接的全视差三维显示方法及图像生成方案.系统核心部分由一个微投影机阵列、一个反射光路和一个散射屏组构成,图像生成方案采用基于OpenGL的算法实现.为了验证所提出的基于视场拼接理论的正确性,利用液晶显示器、菲涅耳镜组、定向散射屏和背投式反射光路搭建了实验样机.该装置可以在更紧凑的系统结构下显示包括横向视差和纵向视差在内的三维图像,并且通过图像生成算法的配合实现了动态三维显示效果.     

新型自动立体显示背光板的光学设计

立体显示技术的研究主要是解决虚拟现实领域的三维视觉问题。自动立体显示是不需要配戴特殊眼镜的,使用一个二维平面空间显示屏显示至少一对满足双眼视差的立体图像。当人的双眼接受到具有视差的立体图像对时,在视网膜上形成视差像,经大脑神经系统的融合,从而产生深度感。提出了一种全新的实现自动立体显示的折射式方法,设计了基于此方法的一种新型折射式的、结构简单的、通过透射显示屏(如液晶显示屏)实现自动立体显示的背光系统。根据视差立体显示参量模型,建立了光学系统的结构参量以及分析了光学材料的性质对实现立体显示的影响,并运用先进的光学设计软件进行设计、模拟。     

小型无人机载大视场复眼相机光学系统设计

针对小型无人机载大视场光学成像观测需求,设计了一款仿生复眼大视场微小型相机.该相机光学系统总焦距为4mm,F数为4,视场角可达106°,在500m的飞行高度分辨率可达0.5m.所设计系统由曲面排布的微透镜阵列、光学像面变换子系统、图像接收和数据采集处理单元三部分组成.仿生复眼中的子透镜采用双胶合透镜组合以减小系统像差,相邻子透镜在满足视场一定重叠率的前提下,可允许相邻多达7个子透镜同时对地面目标进行成像,达到目标定位和测速的目的.仿真结果表明无人机载大视场复眼相机系统在给定的公差范围内像质满足要求,每个通道的光学畸变可控制在1.2%以下.     

集成成像三维显示系统显示性能的研究进展

集成成像三维显示技术是利用透镜阵列获取和显示立体图像的一种三维显示技术。本文首先综述了集成成像三维显示系统的特点,考虑其系统性能主要受分辨率、景深和观看视场角的限制,对近年来集成成像三维显示系统在增大分辨率、景深和观看视场角方面的研究进展做了综合论述,比较分析了各种改进方法的优劣。最后,对我国集成成像三维显示技术的研究现状进行了总结,并简述了本研究小组在该领域取得的若干研究成果。     

微小型快照式傅里叶变换成像光谱仪的建模与分析

为了实时探测运动场景、迅变目标的图像与光谱,提出了一种微小型快照式傅里叶变换成像光谱仪,利用多级微反射镜对微透镜阵列形成的多重像场进行分布式相位调制,实现了干涉图谱信息的实时获取。根据微透镜阵列与多级微反射镜对光场的相位调制特性,建立了多重干涉成像的理论模型,计算表明,不同视场的干涉像点位于探测平面的不同区域,但大视场情况下相邻通道之间的干涉图像单元会发生串扰,并导致复原光谱失真。分析表明,为了抑制相邻干涉成像通道间发生串扰,视场角应控制在微透镜阵列和多级微反射镜的衍射与离焦效应所限定的极限视场角之内。同时,视场角还会引入相位误差,并导致归一化光谱误差随视场角的增大而单调递增。根据归一化光谱误差关系曲面可以对系统的视场角进行合理的设计,从而实现对目标场景中特定区域的有效探测。     

狭缝光栅、柱面透镜光栅及其新构型在三维显示中的应用

介绍了三维显示技术的研究现状,综述了狭缝光栅和柱面透镜光栅在自由立体显示技术中的重要应用。回顾了各种光栅式自由立体显示系统的结构和原理;提出了如何根据狭缝光栅和柱面透镜光栅的特殊光学性质,在传统的立体显示系统中添加各种光栅形成灵活组合结构来提高立体显示效果,强调了它们在减小串扰、增大视场角、避免摩尔条纹以及提供更全面的三维信息等方面的作用。最后指出基于两种光栅的叠加构成面积大、参数均匀、价格低廉的新型透镜可实现全视差立体显示,对探索自由立体显示技术的研究很有意义。     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Hybrid Wavelength and Code Division Multiple Access in Optical Networks

A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.