Waveguide design and application with transformation optics

Waveguide design becomes more and more important with the increasing demand of efficient routing and interconnection of electromagnetic signals for advanced information technologies. Here we review the basic theory, special techniques, and potential applications of transformation optics in waveguide design. Three major design strategies of transformation optics and their limitations in waveguide applications are discussed. The recent new trends of transformation techniques by imposing specific restrictions from materials are emphasized for practical implementation. Plasmonic waveguide is used as an example to compare these transformation strategies. Applications beyond waveguides but with great practical value such as super-resolution hyperlens design are also discussed in the context of waveguiding phenomena from the perspective of transformation optics.     

远场光学探测与近场光学探测

介绍了远场光和近场光的物理图景 ,根据它们的不同性质并结合应用 ,指出远场光学探测的空间分辨能力受光学衍射极限的约束 ,近场光学探测可以突破光学衍射极限。应用近场光学设计新的传感器和探测器 ,能够提高灵敏度和分辨力     

Modes computation in arbitrarily shaped waveguides by a transformation optics approach

This article applies a new method to analyze modes in empty waveguides having perfectly conducting walls and a rather generic cross‐section. The method is based on a coordinate transformation that maps the generic profile of the waveguide cross‐section to a circular waveguide (CW) filled with an anisotropic material. Modes in this latter waveguide can be represented as a series over the corresponding free‐space CW modes. This representation is particularly useful if used as a modal expansion over the port of a 2.5D or 3D device treated with a transformation optics approach. The method is particularly efficient when the waveguide is “similar” to a CW. Applications are shown to the analysis of some waveguides of arbitrary cross‐section with a view on practical applications.     

Making structured metals transparent for broadband electromagnetic waves

In this review, we present our recent work on making structured metals transparent for broadband electromagnetic waves by surface plasmons （SPs） or spoof surface plasmons （SSPs）. First, we demonstrate that the interference between the localized and propagating SPs plays an important role in the optical transmission through arrays of sub-wavelength holes. The observed phenomena belong to the category of plasmonic Fano effects. Second, we show that the transmission enhancement originates not only from the coupling between the incident light and the excited SPs but also from the coupling among these SPs in multiple nano-aperture stacks. Finally, we demonstrate that metallic plates with narrow slit arrays can become transparent within extremely broad spectral bandwidths, and high transmission efficiency is insensitive to the thickness of the metal. This phenomenon explicitly demonstrates the conversion between light and SPs. These investigations provide guidelines to develop many novel materials and devices, such as transparent conducting panels, antireflective solar cells, and other broadband metamaterials.     

油画相似度的表面光场特征点分布鉴别

目的 油画区别于其他绘画形式的重要特征之一是其颜料图层存在厚度变化。因此,油画相似度鉴别不仅关注油画的纹理色彩细节,也需考虑其表面颜料厚度的差异。针对颜料厚度的细微变化,提出一种油画相似度的表面光场特征点分布鉴别方法。采用光场成像技术观测由于油画表面厚度起伏导致的不同角度成像的差异,以量化计算油画表面光场的相似性。方法 该方法采用一块微透镜阵列板对油画表面的角度域变化进行光场编码,利用光场相机采集编码后的油画表面光场。在此基础上,选取油画表面光场中角度域差异大的特征点集合,采用K-Means方法对该特征点集合的二维分布进行多边形向量化描述。进而提出计算关键点连接线的欧氏距离与线段夹角,以度量表面光场特征点分布多边形的相似性。结果 采用Illum光场相机拍摄了多组真实油画的表面光场实验数据,实验结果表明本文方法可对存在细微颜料厚度差别的油画相似度进行鉴别。在对油画表面光场的识别区分度以及检测精度方面,本文方法显著优于现有图像特征匹配鉴别方法。结论 实验分析表明,相比于经典交并比及相似度系数,所提出油画相似性度量具有更优的相似性度量精度。通过调整编码板与测试油画表面距离的反复实验,验证所提方法能够有效检测0.5 mm以上厚度变化的表面光场差异。     

光场数据压缩研究综述

光场数据体量大,为存储和压缩带来巨大困难。由于光场数据格式与传统图像视频数据不同,现有图像视频编码工具难以高效压缩光场数据。因此,光场数据高效压缩研究对降低存储消耗和传输带宽具有重要意义。目前,光场压缩的研究越来越深入,提出的方法种类也越来越丰富。本文对现阶段光场压缩进行系统综述,为后续研究者提供研究基础。本文简要介绍了光场的基本理论及四类光场采集设备,分析了4类采集设备的优缺点,阐明了光场采集方式对光场数据格式的影响;介绍了国际标准组织联合图像专家组（JPEG）在光场压缩标准化方面的最新进展,对JPEG Pleno光场编码器的每个模块做了详细介绍;在广泛文献调研的基础上,将光场压缩算法分成3类：基于变换的压缩方法、基于伪视频序列的压缩方法和基于预测的压缩方法,对每类算法进行详细梳理和总结,并做了详细地对比分析。通过系统地梳理,凝练出光场压缩近期的进展和尚存在的问题,并对未来光场压缩的研究趋势进行展望。实现光场的高效压缩非常具有挑战性,虽然光场压缩研究近期迅猛发展,但是压缩性能仍有待进一步提高。     

量子光学优化算法*

通过分析光学优化算法的特性,将光学优化算法中每个光源点都用量子空间中的一个粒子来描述,利用群体智慧的聚集性,建立了光学优化算法的量子势能场模型,并根据势能场模型的群体自组织性和协同性等特点提出了量子光学优化算法。通过对多个经典测试函仿真分析,得出量子光学优化算法在量子力学收敛理论下比光学优化算法控制参数少,设置简单,优化性能更好,收敛速度更快,优化了算法的收敛精度和速度。     

光场显著性检测研究综述

显著性检测一直是计算机视觉领域的关键问题,在视觉跟踪、图像压缩和目标识别等方面有着非常重要的应用。基于传统RGB图像和RGB-D （RGB depth）图像的显著性检测易受复杂背景、光照、遮挡等因素影响,在复杂场景的检测精度较低,鲁棒的显著性检测仍存在很大挑战。随着光场成像技术的发展,人们开始从新的途径解决显著性检测问题。光场数据记录着空间光线位置信息和方向信息,隐含场景的几何结构,能为显著性检测提供可靠的背景、深度等先验信息。因此,利用光场数据进行显著性检测得到了广泛关注,成为研究热点。尽管基于光场数据的显著性检测算法陆续出现,但是缺少对该问题的深刻理解以及研究进展的全面综述。本文系统地综述了基于光场数据的显著性检测研究现状,并进行深入探讨和展望。对光场理论以及用于光场显著性检测的公共数据集进行介绍;系统地介绍了光场显著性检测领域的算法模型和最新进展,从人工设计光场特征、稀疏编码特征和深度学习特征等方面进行全面阐述及分析;通过4个公共光场显著性数据集上的实验数据对不同方法的优缺点进行比较和分析,并结合实际应用指出当前研究的局限性与发展趋势。     

开放分布式苹果采摘机器人控制系统研究及实现

针对以往采摘机器人多采用封闭集中式控制系统,缺乏通用性、可扩展性差和可靠性低等问题,在研制开发苹果采摘机器人控制系统的工作中,采用了开放分布式结构.根据苹果采摘机器人的机械结构及其运动特点,在硬件上选用工控机、伺服驱动器等设备,通信上采用结构简单、组网容易、造价低廉的RS-485网络,从而保证了系统的软硬件开放性,同时使得系统能够分布式控制,提高了机器人的安全性.此外,对系统的控制算法、软件也进行了设计,其中着重阐述了RS-485网络的通信协议和通讯方式.最后进行了通讯试验和苹果抓取试验,验证了系统的有效性.     

Discrete-time model for an adaptive optics system with input delay

The standard adaptive optics (AO) system can be viewed as a sampled-data feedback system with a continuous-time disturbance (the incident wavefront from the observed object) and discrete-time measurement noise. A common measure of performance of AO systems is the time average of the pupil variance of the residual wavefront. This performance can be related to that of a discrete-time system obtained by lifting the incident and residual wavefronts. This article derives the corresponding discrete-time model and the computation of the AO system residual variance based on that model. The predicted variance of a single mode of an AO system is shown to be the same as that obtained via simulation.     

具有能量补给的无线传感器网络分簇路由算法

提出一种具有能量补给的无线传感器网络分簇路由算法PHC。在PHC中,传感器节点通过周围环境获取能量补给。PHC综合考虑节点自身的能量起伏变化以及能量补给水平,修正了现有的簇头选择机制和非簇头节点的归属机制,使能量消耗平均分配到整个网络中。通过仿真表明,PHC在考虑了能量补给的同时,改善了无线传感器网络中能量消耗的均衡性,延长了网络的生命周期,网络中最终存活节点和整体残留能量提高了20%。     

Three‐dimensional lenticular display synthetic image rendering based on light field acquisition

Crosstalk is a critical defect affecting image quality in multiview lenticular 3D displays. Existing optimization methods require tedious computations and device‐specific optical measurements, and results are often suboptimal. We propose a new method, on the basis of light field acquisition and optimization, for crosstalk reduction in super multiview displays. Theory and algorithms were developed, and experimental validation results showed superior performance.     

带有NES-GMM的弹性支撑梁振动控制及能量采集研究

本文针对带有非线性能量阱-超磁致伸缩材料 (NES-GMM) 的弹性支承梁的振动抑制及能量采集问题开展了研究.基于哈密顿原理、伽辽金方法并考虑GMM的本构关系,推导了梁、NES及GMM的耦合控制方程.利用四阶龙格库塔方法对谐波激励下梁的响应进行了数值分析.本研究首先从时域和频域两个方面分析了NES-GMM对梁的振动抑制效果,随后探讨了外界激励频率变化对NES-GMM装置能量耗散及采集性能的影响.此外,本文还分析了NES的非线性刚度、线性阻尼、惯性系数及NES-GMM加载位置等参数对振动控制和能量采集效果的影响.研究结果表明,NES-GMM 系统能有效降低弹性支承梁在谐波激励下的多模态横向振动,并在振动抑制与能量采集两方面展现出良好的独立性能.     

基于能量捕获和混合储能的微观网络能量最优分配算法

随着纳米技术和无线网络技术的快速发展,单个节点(设备)的微小尺寸和有限能量严重地限制了微观无线网络的应用。因此,在传统宏观网络节点储能结构单一和能量捕获技术不稳定的基础上,利用超级电容的快速充放电特性,提出了一种基于超级电容和电池的混合储能结构。在此混合储能结构的基础上,根据点对点的双工信道模型和能量传输损耗特性,建立了面向能量捕获的网络吞吐量模型和节点能量分配解析模型,并提出了相应的能量最优分配算法,实现了节点吞吐量的最大化。该算法根据节点捕获能量的时域分布,优化分配超级电容与电池的能量值;同时,采用最优传输功率与传输时间进行数据传输。实验结果表明,所提混合储能结构和能量分配算法能有效地提高节点的吞吐量。     

Virtual viewpoints reconstruction via Fourier slice transformation

We propose a new method of calculating the arbitrary viewpoints for auto‐stereoscopic display. The three‐dimensional (3D) object is first virtually reconstructed in 3D spaces by mapping each pixel with a depth according to the depth mapping. We then calculate the Fourier spectrum of the 3D object by the fast Fourier transformation. The arbitrary viewpoints are reconstructed by “slicing” the 3D Fourier spectrum. To repair “black hole” artifacts, the regions in the background are calculated by advanced boundary in‐painting. Experimental results show the effectiveness and accuracy of the proposed algorithm to calculate viewpoints with arbitrary viewing angles. A comparison is also presented, which indicates that the proposed algorithm is more accurate than conventional method, and the advanced boundary in‐painting can save three quarters of time than the conventional in‐painting method.     

融合边缘特征的高效光场深度信息估计算法

为解决基于光场传统EPI(epipolar plane image)结构的深度信息估计算法执行效率低和估计精度低的问题,提出一种融合边缘特征的高效光场深度信息估计算法。改进传统EPI结构为包含完整像素极线信息的IEPI(improved epipolar plane image)结构和对应包含边缘信息的边缘图;构建深度多流全卷积神经网络,学习IEPI及边缘图的特征;构建基于尺度不变误差的代价函数,结合HCI光场数据集指导网络训练,实现一个估计光场深度信息的网络。实验结果表明,所提算法相较于传统算法提升了估计精度和估计效率。     

Direct light field rendering without 2D image generation

Rapid developments in 3D display technologies have enabled consumers to enjoy 3D environments in an increasingly immersive manner through various display systems such as stereoscopic, multiview, and light field displays. However, there is a corresponding increase in the complexity of the conventional multiview rendering process in the attempt to achieve a sufficient level of reality, which may hinder the further commercial viability of 3D display products based on such a conventional approach. This paper proposes a novel method, the so‐called direct light field rendering, which can compose the display 3D panel image without reconstructing all the multiview images beforehand. Interpreting the 3D display as sampling in the light field domain, we attempt to directly compute only the necessary samples, not the entire light fields or multiview images. Our proposed algorithm involves the solving of linear systems of two variables, thereby requiring remarkably low computational complexities. Experimental results show that the computation time and memory usage remain as little as 12% and 1% of those required by the conventional one.     

特征融合网络：多通道信息融合的光场深度估计

摘 要：光场相机可以仅在一次拍摄中记录场景的空间和角度信息,所生成的图像与传统 二维图像相比包含了更多的信息,在深度估计任务方面更具有优势。为了利用光场图像获取高 质量的场景深度,基于其多视角的表征方式,提出了一种具有多通道信息高效融合结构的特征 融合网络。在人为选择特定视角的基础上,使用不同尺寸卷积核来应对不同的基线变化;同时 针对光场数据的多路输入特点搭建了特征融合模块,并利用双通道的网络结构整合神经网络的 前后层信息,提升网络的学习效率并减少信息损失。在 new HCI 数据集上的实验结果显示,该 网络在训练集上的收敛速度较快,可以在非朗伯场景中实现精确的深度估计,并且在 MSE 指 标的平均值表现上要优于所对比的其他先进的方法。     

基于奇相干光源和量子存储的量子密钥分配协议

针对传统量子密钥分配协议使用弱相干光源带来的密钥生成率较低的问题,对光源进行优化,用奇相干光源代替弱相干光源,提出了基于奇相干光源和量子存储的测量设备无关量子密钥分配协议。对比了具有奇相干光源和量子存储的测量设备无关量子密钥分配协议与基于弱相干光源测量设备无关量子密钥分配协议的性能优劣。分析了基于奇相干光源和量子存储的测量设备无关量子密钥分配协议中,密钥生成率、最小退相干时间与安全传输距离之间的关系。仿真结果表明,引入奇相干光源大大减少了传统弱相干光源的多光子数,弥补了其在光源上的不足之处。随着安全传输距离的增加,密钥生成率随之降低,但基于奇相干光源和量子存储的量子密钥分配协议性能仍然较高。