光学超分辨平面超构透镜研究进展

从光学自身机理上突破光学理论分辨率极限,实现远场超分辨光学点扩散函数,进而实现超分辨聚焦和超分辨成像,在激光加工、超分辨光学显微和超分辨望远等系统有着重要应用前景.近年来,光学超构表面的发展使得在亚波长尺度上实现光场振幅、相位及偏振的独立调控成为可能,为研制新型的超分辨平面超构透镜提供了更加灵活的手段.本文介绍了基于光学超构表面的超分辨平面超构透镜、相关测试技术方面几年来的研究进展,并讨论了该领域面临的问题和未来的研究重点和方向.     

微透镜列阵成像光刻调焦方法

本文分析了离焦量对微透镜列阵成像光刻图形质量的影响,给出了系统离焦量的容差.同时提出了一种结构简单、可应用于微透镜列阵成像光刻系统调焦的新方法.并将基于该调焦方法的实验装置应用于微透镜列阵成像光刻系统,进行了光刻实验.实验表明,利用该方法时微透镜列阵成像光刻系统调焦,可得到接近微透镜列阵极限像质的光刻图形.     

用灰度曝光技术改善数字光刻图形轮廓

基于空间光调制器(SLM)数字光刻技术可用于IC掩模制作或直接作为微结构的加工工具,但用数字投影光刻系统加工某些结构的二元图形时,往往难以获得预期的图形轮廓,即图形边缘处有一定畸变,特别是较低缩小倍率时。本文提出优化设计图形边缘灰度的方法来校正光刻图形的畸变。文中分析了数字光刻制作这些二元光刻图形时空间像畸变产生的物理机制,详细讨论了设计图形边缘灰度优化的规则,并以加工圆孔滤波器为例,模拟了它的数字光刻成像过程。结果表明,设计图形的边缘采用灰度曝光可使其空间像畸变减小约8个百分点,光场分布更为均匀。数字灰度曝光技术简单易行,可为改善光刻图形质量提供了新途径。     

接近式光刻图形失真的部分相干光理论分析

光刻过程中由于光的衍射效应产生的非线性畸变对光刻面形质量具有严重影响，是造成光刻微结构图形失真的主要原因之一，为此，研究了接近式紫外光刻中部分相干光的传播过程，建立了相应的光刻理论模型，对光刻成像中的误差产生机理进行分析．该模型综合考虑光源和照明系统对掩模微结构附近光场相干性的影响，将光刻模拟分为3部分．首先根据VanCittert-Zernike定理确定了光源经扩束准直系统传播到蝇眼透镜入射面时光场上任2点的互强度．然后应用部分相干光的传播理论，由Hopkins公式得到部分相干光经蝇眼透镜传播到掩模平面后其上任一点对的复相干度的分布规律．最后根据互强度传播定律，分析从掩模面到光刻胶表面的衍射效应，得到光刻胶表面的光强分布及变化规律，并且通过误差的仿真分析模拟得到光刻胶图形轮廓．结果表明，理论模拟结果与实验较为吻合．该方法能准确地得到衍射光场的分布，进行光刻误差分析，从而能较好地发现曝光图形缺陷．     

用于大面积周期性图形制造的激光干涉光刻

用两束或多束相干激光束以不同的组合形式对光致抗蚀剂曝光,可在大面积范围内产生精细的二维周期性图形,这个方法特别适合于产生光电子器件和生电子器件的周期性结构。介绍激光干涉光刻的基本原理,对几种光束组合干涉方法给出了理论推导结果,并进行了计算机模拟。初步的实验结果表明,用激光干扰光刻技术产生大面积的亚微米级周期性孔、柱、锥图形是可行的。该方法不需要掩模、昂贵的光刻成像透镜、新的短波长光源和新型的抗蚀剂,提供了得到高分辨、无限焦深、大面积光刻的可能性。     

超材料的应用及制备技术研究进展

超材料是一类具有特殊性质、自然界中并不存在的人造材料。综述了单负超材料和左手超材料构型的研究进展和超材料在超分辨成像、电磁隐身和电磁吸波体等方面的应用。同时也对国内外主要超材料制备技术进行了分类和概述,包括电子束光刻、纳米压印技术和聚焦离子束技术等。最后对超材料的发展方向和应用方向进行了展望。     

超分辨近场光学成像技术及其产业开发

超分辨近场光学成像技术是当前国内外一个重要的高新技术前沿课题,也将是我国21世纪初应该发展的一项高新技术产业。文中介绍了我国自1991年以来开拓研究的进展,探讨了国际学术界及产业开发中当前存在的主要问题,提出了各类超分辨扫描模式成像公式的乘法表达式,并作了分析比较。为解决消除假像和从有形貌等混合图像中分离纯光学图像两大难题,作者曾于1993年和1996年提出两项发明专利,为发展我国的该产业解决了两大技术关键。     

三维场景的光场成像仿真

针对光场数据获取困难的问题,本文根据Levoy的光场渲染理论设计出了一种三维光场信息获取的仿真方式.在物空间构建问题上,以最靠近主透镜的物面为起点向后进行扩展,形成了一个离散的物空间.为了解决近景对远景的遮挡问题,按照金字塔模型,由最靠近主透镜的物面开始逐渐对其后的物面有效区域进行扩展,计算各离散物面的有效区域经过主透镜的积分值.对于离焦物点,通过计算光斑在每个微透镜上的权重,赋予该微透镜下对应像元相应比例的光线强度.最后,通过对仿真实验所得到的光场图像进行不同物距的重聚焦,验证所建三维模型及光场成像仿真的正确性.实验结果表明:本文所提出的三维场景的光场成像方式能够有效地得到该场景的光场数据.     

角度差异强化的光场图像超分网络

由于采用了更为先进的成像技术，光场相机可以同步获取场景的空间信息与角度信息。该技术以牺牲空间分辨率为代价，实现了更高维度的场景表示。为了提高光场相机拍摄场景的空间分辨率，本文搭建了角度差异强化的光场超分辨率重构网络。该网络先采用8个多分支残差块实现浅层特征提取，再采用4个强化的角度可变形对准模块实现深层特征提取，最后采用6个简化的残差特征蒸馏模块和像素洗牌模块完成数据重构。所提网络在利用光场角度差异完成空间信息超分时，更加强调视图自身特征的深入挖掘，以获得更加丰富的视图间差异特征。在5组公开的光场数据集上对本文所提网络的性能进行了验证，本文算法获得了PSNR、SSIM值更高的高分辨率光场子孔径图像。     

超表面光场调控专题导读

<正>作为一种新概念，超(构)表面通过对亚波长尺寸的单元结构进行优化设计和合理排列，能够控制光的振幅、相位、偏振等光参量及其色散特性，进一步可以控制宏观波前分布，提供了一种强大的光场调控方式。得益于小像素尺寸和强光场调控能力，超表面在超透镜、分光器、雷达天线等应用领域已经展露锋芒，     

Spiral hyperlens with enhancements of image resolution and magnification

Abstract

A subwavelength spiral hyperlens that is able to image beyond the diffraction limit is studied. The spiral hyperlens is made from an anisotropic metamaterial with a hyperbolic dispersion relation in which the evanescent wave is converted into a propagating wave. Therefore, the propagating wave can be processed by conventional optical systems outside of the spiral hyperlens. The possibility of using a cylindrical hyperlens for overcoming the diffraction limit has been proven analytically and experimentally. In this study, we designed two types of spiral hyperlenses composed of a spiral periodic stack of silver and alumina multilayers. A spiral hyperlens utilizes the spiral geometry to magnify the objects. In comparison with a cylindrical hyperlens, a spiral hyperlens has improved performance in terms of higher image resolution and better image magnifications. Numerical simulations illustrate that the far-field imaging resolution of cylindrical spiral hyperlens is no greater than 110 nm at 365 nm working wavelength.     

Two-dimensional subwavelength imaging from a hemispherical hyperlens

We report a hemispherical-shaped hyperlens with subwavelength resolution less than 100 nm. Simulations with the finite-element method show that with a 365 nm illumination, the hemispherical hyperlens isotropically magnifies the image along the radial direction. Under linearly polarized light, portions of an object can be resolved. A complete image of the object can be generated by superposing sufficient number of images obtained with incident light in different polarization directions. Such a hyperlens has great potential for realization of nanoscale imaging.     

A super-oscillatory lens optical microscope for subwavelength imaging

The past decade has seen an intensive effort to achieve optical imaging resolution beyond the diffraction limit. Apart from the Pendry-Veselago negative index superlens, implementation of which in optics faces challenges of losses and as yet unattainable fabrication finesse, other super-resolution approaches necessitate the lens either to be in the near proximity of the object or manufactured on it, or work only for a narrow class of samples, such as intensely luminescent or sparse objects. Here we report a new super-resolution microscope for optical imaging that beats the diffraction limit of conventional instruments and the recently demonstrated near-field optical superlens and hyperlens. This non-invasive subwavelength imaging paradigm uses a binary amplitude mask for direct focusing of laser light into a subwavelength spot in the post-evanescent field by precisely tailoring the interference of a large number of beams diffracted from a nanostructured mask. The new technology, which--in principle--has no physical limits on resolution, could be universally used for imaging at any wavelength and does not depend on the luminescence of the object, which can be tens of micrometres away from the mask. It has been implemented as a straightforward modification of a conventional microscope showing resolution better than λ/6.     

变增量扫频法求解结构随机风振响应

结构耦合抖振响应有限元分析的完全二次组合(CQC)频域方法在数值积分过程中,一般都采用等增量扫频。大型结构的实际频响函数一般只有在共振频率附近才有较大的数值,而在其他远离共振频率点的区域频响函数值都很小。基于此,该文提出结构抖振响应变增量扫频的频域分析法。采用基于完全二次组合的CQC法编制结构抖振响应变增量扫频计算程序,该程序在做数值积分的时候采用变增量扫频的方式,在结构共振频率点附近自动加密计算点,而在其他的频率区则间采用较大的增量步长。以某大桥为例,对等增量扫频法和变增量扫频法得到的结果进行比较,证实了变增量扫频法在保证求解精度的前提下能大大的缩短求解的时间,提高效率。     

Assembly line balancing: a set of challenging problems

Various techniques have been proposed for solution of the assembly line balancing problem. To demonstrate their efficacy, sample problems have been employed. In recent years, a common set of problems have often been used. This paper examines that set and shows that in light of the state of the art in algorithm development and computer technology, the existing literature set is inadequate as a benchmark. A new set of problems, based upon the previous set, but which is more challenging is proposed. A simple, but effective algorithm is employed to allow focus on the problems; a commonly available microcomputer, easily compared with mainframes or other micros, is employed for timing results.     

A DISTRIBUTED FINITE ELEMENT METHOD FOR SOLVING THE INCOMPRESSIBLE NAVIER–STOKES EQUATIONS

The potential for using a network of workstations for solving the incompressible Navier–Stokes equations using a finite element formulation is investigated. A programming paradigm suitable for a heterogeneous distributed workstation environment is developed and compared to the traditional paradigm employed for distributed memory parallel computers. In particular, the issues of load balancing and fault recovery are explored. Numerical results are presented for two computer configurations: (1) a homogeneous network of workstations and (2) a heterogeneous network of workstations. The superiority of the developed paradigm over the traditional paradigm employed for distributed memory parallel computers is shown in cases where a heterogeneous network of workstations is employed or when one of the workstations of the cluster is loaded by other users.     

Measurement of the relationship between perceived and computed color differences

Using simulated data sets, we have analyzed some mathematical properties of different statistical measurements that have been employed in previous literature to test the performance of different color-difference formulas. Specifically, the properties of the combined index PF/3 (performance factor obtained as average of three terms), widely employed in current literature, have been considered. A new index named standardized residual sum of squares (STRESS), employed in multidimensional scaling techniques, is recommended. The main difference between PF/3 and STRESS is that the latter is simpler and allows inferences on the statistical significance of two color-difference formulas with respect to a given set of visual data.     

Determining optimum operating characteristics for a continuous processing machine centre

The purpose of this paper is to illustrate an approach to determining a minimum cost operating regimen for n continuous processing machine centre. A variational analysis is employed to determine an optimal processing trajectory, and from this an approach to establishing an upperbound on the theoretical number of machines employed in processing can be established     

一种多阶段供应商选择的混合整数规划模型

在建立供应链合作伙伴关系中,供应商的选择是供应链管理的一项重要内容.在现有文献的基础上对供应商的选择模型进行了改进,建立了集成单阶段与多阶段供应商选择的混合整数规划模型:既可以选择单阶段供应商,也可选择多阶段供应商即供应商的供应商的供应商等等.在模型中考虑了每个潜在供应商的能力约束,以供应商在产品价格、质量、配送水平等三个方面引起总的客户不满意度最小化作为选优的依据.