部分相干成像系统分辨极限研究

部分相干理论的引入丰富了光学成像分辨领域的研究,相较于理想情况下的完全相干和完全非相干光照明两点成像系统,部分相干成像系统的分辨率显著提升。本文设计了部分相干光照明两点成像系统,建立像面光强分布的数学模型,利用MATLAB仿真模拟不同空间相干性光源产生的辐射特性和两点间距对成像分辨的影响;并给出部分相干成像系统分辨极限的判定方法:当且仅当像面光强分布的峰值和谷值相等时可判定两点光源恰可分辨;以及不同相干度的光源照明成像系统分辨率的计算方法和差异。同时设计并搭建实验平台,实验结果验证了相干度分别为0、0.9和1.0时,成像分辨极限分别为1.0 mm、1.4 mm和1.5 mm,误差范围小于5%,说明实验结果与理论结果吻合。     

相干光照明下无衍射系统的点扩散函数的测量

在分析相干光照明下无衍射成像系统理论的基础上,设计了无衍射光成像系统的点扩散函数的测量系统。利用菲涅耳衍射理论,推导出相干光照明下无衍射系统的点扩散函（PSF）的形式,并分析出点扩散函数的条纹疏密与锥镜的夹角和点光源的位置有关。实验和仿真结果表明,点扩散函数的条纹间距随锥镜夹角增大而变窄,随点光源距透镜距离的增大而变窄。     

基于迈克耳孙干涉仪的非相干数字全息显微成像

采用基于迈克耳孙干涉仪的非相干数字全息显微成像系统能够得到物体在非相干光照明下的全息图。对基于迈克耳孙干涉仪的非相干数字全息显微成像系统进行了理论和实验研究。利用标量衍射理论计算了该系统在记录过程中的点扩展函数,获得了系统横向放大率及重建距离的具体表达式。搭建了基于迈克耳孙干涉仪的非相干数字全息显微成像系统的实验光路,利用CCD记录全息图,用广义相移数字全息干涉术去除孪生像与零级像,并用角谱算法得到了清晰的重建像。实现了分辨率板和洋葱表皮细胞等样品的非相干全息显微成像,验证了该系统的可行性。分辨率板的成像实验表明,该系统的横向分辨率可达512lp/mm。微米洁面刷软毛的成像实验表明,该系统具有呈现物体三维结构的特性。     

自干涉非相干全息成像系统分辨率

基于拉格朗日不变量法则,与经典光学成像系统分辨率对照,分别对自干涉非相干数字全息(SIDH)成像系统的横向以及轴向分辨率展开讨论。通过系统放大率及点扩展函数半峰全宽的计算,从理论上给出系统横向和轴向分辨率,以及系统分辨本领判断准则的具体数学表达式。并与经典光学成像系统对比,指出当全息记录面位于来自物光点的两束球面光波光斑的完全重合处时,自干涉非相干全息成像系统的横向超分辨率提高了一倍。引入压缩感知数值重构算法改善系统轴向分辨率,并给出相应的数值模拟及实验结果。研究结果对自干涉非相干数字全息术在成像、测量以及光路设计方面具有重要的指导意义。     

赋形像元探测器在超分辨重建中的应用

大多数光电成像系统的空间分辨率都与探测器的元数密切相关,增加探测器的元数是提高成像系统空间分辨率的核心问题之一.在不增加探测器元数的前提下,提高空间分辨率的技术途径之一就是超分辨重建技术,它通过增加探测器采样频率来提高探测器的空间分辨率.考虑到探测器的空间分辨率并不完全取决于采样作用,且受像元孔径效应的影响,提出了一种赋形像元探测器.基于巴比涅原理中的互补屏原则,将原有的红外探测器中的每个正矩形像元去掉1/4,用剩余部分来等效获取去掉部分的高截止频率;同时利用两列赋形像元探测器进行亚像元推扫,结合像元细分算法,实现超分辨重建.通过同时提高系统采样频率和探测器的截止频率来实现红外系统最终的高分辨率重建成像.     

部分相干光照明正弦振幅光栅偏振成像的研究北大核心CSCD

偏振成像由于其能检测物体偏振信息并可有效抑制背景噪声信号而受到了广泛关注。以往对正弦振幅光栅成像的研究基本都是在完全相干、非相干、或部分相干照明条件下进行,而本文基于偏振相干统一理论,在部分相干照明条件下考虑了光的偏振态,设计了部分相干光照明正弦振幅光栅的偏振成像系统,据此系统得出其斯托克斯(Stokes)频域计算模型,提供了一种计算Stokes物像频域关系的方法,通过透射交叉系数来描述其偏振成像系统的频率响应,说明偏振成像系统是非线性的,对光栅像强度中直流分量、基频、二次谐波进行分析研究,给出一组归一化Stokes参数下部分相干光照射正弦振幅光栅像面强度图,并利用MATLAB绘制出几组不同物体照明相干间隔与成像系统衍射图样大小比率下的Stokes像强度图,扩展了正弦轨迹分析在偏振成像系统性能评估中的应用。     

非相干同轴数字全息显微成像研究

采用非相干光作 为光源,空间 光调制器(SLM)和CCD组成非相干干涉仪作为全息记录模块,结合物镜搭建了非相干同轴数 字全息显微成像 系统。采用该系统对分辨率板成像,实现了512lp/mm的空间分辨率 ,并对系统放大率进行了标定。用草本 植物茎横切细胞作为测试样品,完成了生物细胞显微观察实验,将数字全息显微术的应用范 围从相干光扩展到了非相干光领域,推进非相干数字全息显微术的应用研究。     

基于Gibbs抽样的红外成像小间距目标分辨方法

利用红外成像系统跟踪多个相距很近的点目标时,目标在成像面上的弥散像会发生交叠,导致成像系统无法有效分辨这些目标.本文提出了一种分辨这类小间距目标(Closely Spaced Objects,CSO)的新方法,通过建立小间距目标的成像模型,采用Gibbs抽样方法对小间距目标在焦平面上的中心位置和响应幅度进行估计,并利用贝叶斯信息准则(Bayesian Information Criterion,BIC)检测目标数目.针对仿真生成的红外图像进行了仿真实验,实验结果表明本文方法对小间距目标的分辨是有效的.     

90°临面入射体全息成像系统的深度分辨率

研究了90°临面入射体全息成像系统的三维成像特性。体全息光栅由球面信号光波和平面参考光波干涉记录,并以原信号光作为探测光波进行成像。当探测点光源的位置发生变化时,由于体全息光栅的布拉格选择性,可引起衍射成像光场的显著变化。利用衍射理论计算体全息成像系统的点扩展函数,评价成像系统的纵度和深度分辨率特性。结果表明,探测点光源的位置沿着z轴移动时,衍射光场变化明显。     

部分相干光经多个圆孔衍射后的偏振度变化

基于随机电磁光束的相干偏振统一理论和部分相干光的传输定律,研究了部分相干光源所发出的光经过多个圆孔衍射后的偏振度变化情况。以高斯-谢尔(Gauss-Schell)模型光束为例,研究了多个圆孔衍射后的轴上偏振度变化。发现随着圆孔数量的增加,偏振度将出现相应的变化,并且经过足够长的传输距离之后,偏振度将趋于一个定值。以三个圆孔为例,重点研究了圆孔大小、圆孔间距、源平面处的相干长度以及源平面的偏振度取值等参量对轴上观察点的偏振度影响。     

Resolution Enhancement Technology:Integrated Process Solutions using OPC

DUV lithography, using the 248 nm wavelength, is a viable manufacturing option for devices with features at 130 nm and less. Given the low kl value of the lithography, integrated process development is a necessary method for achieving acceptable process latitude. The application of assist features for rule based OPC requires the simultaneous optimization of the mask, illumination optics and the resist.Described in this paper are the details involved in optimizing each of these aspects for line and space imaging.A reference pitch is first chosen to determine how the optics will be set. The ideal sigma setting is determined by a simple geometrically derived expression. The inner and outer machine settings are determined, in turn,with the simulation of a figure of merit. The maximum value of the response surface of this FOM occurs at the optimal sigma settings. Experimental confirmation of this is shown in the paper.Assist features are used to modify the aerial image of the more isolated images on the mask. The effect that the diffraction of the scattering bars (SBs) has on the image intensity distribution is explained. Rules for determining the size and placement of SBs are also given.Resist is optimized for use with off-axis illumination and assist features. A general explanation of the material' s effect is discussed along with the affect on the through-pitch bias. The paper culminates with the showing of the lithographic results from the fully optimized system.     

Cost-effective test solutions for smart card and other integrated flash applications

From its emergence in the late 1980s as a lower cost alternative to early EEPROM technologies, flash memory has evolved to higher densities and speedsand rapidly growing acceptance in mobile applications.In the process, flash memory devices have placed increased test requirements on manufacturers. Today, as flash device test grows in importance in China, manufacturers face growing pressure for reduced cost-oftest, increased throughput and greater return on investment for test equipment. At the same time, the move to integrated flash packages for contactless smart card applications adds a significant further challenge to manufacturers seeking rapid, low-cost test.     

Theoretical analysis of the relationship between the Brillouin gain coefficient and the strain in the optical-fiber sensors

The relation between the power of the Brillouin signal and the strain is one of the bases of the distributed fiber sensors of temperature and strain. The coefficient of the Bfillouin gain can be changed by the temperature and the strain that will affect the power of the Brillouin scattering. The relation between the change of the Brillouin gain coefficient and the strain is thought to be linear by many researchers. However, it is not always linear based on the theoretical analysis and numerical simulation. Therefore, errors will be caused if the relation between the change of the Brillouin gain coefficient and the strain is regarded as to be linear approximately for measuring the temperature and the strain. For this reason, the influence of the parameters on the Brillouin gain coefficient is proposed through theoretical analysis and numerical simulation.     

An improved parallel thinning algorithm with two subiterations

The parallel thinning algorithm with two subiterations is improved in this paper. By analyzing the notions of connected components and passes, a conclusion is drawn that the number of passes and the number of eight-connected components are equal. Then the expression of the number of eight-connected components is obtained which replaces the old one in the algorithm. And a reserving condition is proposed by experiments, which alleviates the excess deletion where a diagonal line and a beeline intersect. The experimental results demonstrate that the thinned curve is almost located in the middle of the original curve connectivelv with single pixel width and the processing speed is high.     

Novel fiber-optical interferometer with miniaturized probe for in-hole measurements

Today, micro-system technology and the development of new MEMS （Micro-Electro-Mechanical Systems） are emerging rapidly. In order for this development to become a success in the long run, measurement systems have to ensure product quality. Most often, MEMS have to be tested by means of functionality or destructive tests. One reason for this is that there are no suitable systems or sensing probes available which can be used for the measurement of quasi inaccessible features like small holes or cavities. We present a measurement system that could be used for these kinds of measurements. The system combines a fiber optical, miniaturized sensing probe with low-coherence interferometry, so that absolute distance measurements with nanometer accuracy are possible.     

Study of waveguide coupling efficiency in hybrid silicon lasers

This paper presents a new method to increase the waveguide coupling efficiency in hybrid silicon lasers. We find that the propagation constant of the InGaAsP emitting layer can be equal to that of the Si resonant layer through improving the design size of the InP waveguide. The coupling power achieves 42% of the total power in the hybrid lasers when the thickness of the bonding layer is 100 nm. Our result is very close to 50% of the total power reported by Intel when the thickness of the thin bonding layer is less than 5 nm. Therefore, our invariable coupling power technique is simpler than Intel＇s.     

Teleportation of an arbitrary unknown N-qubit entangled state under the controlling of M controllers

A new quantum protocol to teleport an arbitrary unknown N-qubit entangled state from a sender to a fixed receiver under M controllers(M < N) is proposed. The quantum resources required are M non-maximally entangled Greenberger-Home-Zeilinger (GHZ) state and N-M non-maximally entangled Einstein-Podolsky-Rosen (EPR) pairs. The sender performs N generalized Bell-state measurements on the 2N particles. Controllers take M single-particle measurement along x-axis, and the receiver needs to introduce one auxiliary two-level particle to extract quantum information probabilistically with the fidelity unit if controllers cooperate with it.     

Diode-end-pumped Nd:YVO4/LBO lasers with 4.2W continuous-wave output at 457 nm

A continuous-wave (CW) 457 nm blue laser operating at the power of 4.2 W is demonstrated by using a fiber coupled laser diode module pumped Nd: YVO4 and using LBO as the intra-cavity SHG crystal With the optimization of laser cavity and crystal parameters, the laser operates at a very high efficiency. When the pumping power is about 31 W, the output at 457nm reaches 4.2 W, and the optical to optical conversion efficiency is about 13.5% accordingly. The stability of the out putpower is better than 1.2% for 8 h continuously working.     

A rigorous proof of MIMO channel capacity’s increase with antenna number

It is well known that adding more antennas at the transmitter or at the receiver may offer larger channel capacity in the multiple-input multiple-output（MIMO） communication systems. In this letter, a simple proof is presented for the fact that the channel capacity increases with an increase in the number of receiving antennas. The proof is based on the famous capacity formula of Foschini and Gans with matrix theory.     

Call for Papers

正Wireless Body-area Networks The last decade has witnessed the convergence of three giant worlds:electronics,computer science and telecommunications.The next decade should follow this convergence in most of our activities with the generalization of sensor networks.In particular with the progress in medicine,people live longer and the aging of population will push the development of wireless personal networks