PC-bzip2: a phase-space continuity-enhanced lossless compression algorithm for light-field microscopy data

Light-field fluorescence microscopy(LFM)is a powerful elegant compact method for long-term highspeed imaging of complex biological systems,such as neuron activities and rapid movements of organelles.LFM experiments typically generate terabytes of image data and require a substantial amount of storage space.Some lossy compression algorithms have been proposed recently with good compression performance.However,since the specimen usually only tolerates low-power density illumination for longterm imaging with low phototoxicity,the image signal-to-noise ratio(SNR)is relatively low,which will cause the loss of some efficient position or intensity information using such lossy compression algorithms.Here,we propose a phase-space continuity-enhanced bzip2(PC-bzip2)lossless compression method for LFM data as a high-efficiency and open-source tool that combines graphics processing unit-based fast entropy judgment and multicore-CPU-based high-speed lossless compression.Our proposed method achieves almost 10%compression ratio improvement while keeping the capability of high-speed compression,compared with the original bzip2.We evaluated our method on fluorescence beads data and fluorescence staining cells data with different SNRs.Moreover,by introducing temporal continuity,our method shows the superior compression ratio on time series data of zebrafish blood vessels.

Multifunctional light-field modulation based on hybrid nonlinear metasurfaces

The generation characteristics of nonlinear optical signals and their multi-dimensional modulation at micro-nano scale have become a prominent research area in nanophotonics,and also the key to developing various novel nonlinear photonics devices.In recent years,the demand for higher nonlinear conversion efficiency and device integration has led to the rapid progress of hybrid nonlinear metasurfaces composed of nanostructures and nonlinear materials.As a joint platform of stable wavefront modulation,nonlinear metasurface and efficient frequency conversion,hybrid nonlinear metasurfaces offer a splendid opportunity for developing the next-generation of multipurpose flat-optics devices.This article provides a comprehensive review of recent advances in hybrid nonlinear metasurfaces for light-field modulation.The advantages of hybrid systems are discussed from the perspectives of multifunctional light-field modulation,valleytronic modulation,and quantum technologies.Finally,the remaining challenges of hybrid metasurfaces are summarized and future developments are also prospected.

SOFFLFM:Super-resolution optical fluctuation Fourierlight-field microscopy

Fourier light-field microscopy(FLFM)uses a microlens aray(MLA)to segment the Fourierplane of the microscopic objective lens to generate multiple two-dimensional perspective views,thereby reconstructing the threedimensional(3D)structure of the sample using 3D deconvo-lution calculation without scanning.However,the resolution of FLFM is stil limited by dif-fraction,and furthermore,it is dependent on the aperture division.In order to improve itsresolution,a super-resolution opticai fuctuation Fourier light-field microscopy(SOFFLFM)wasproposed here,in which the super-resolution optical fluctuation imaging(SOFI)with the abilityof super-resolution was introduced into FLFM.SOFFLFM uses higher-order cumulants statis-tical analysis on an image sequence collected by FLFM,and then carries out 3D deconvolutioncalculation to reconstruct the 3D structure of the sample.The theoretical basis of SOFFLFM onimproving resolution was explained and then verified with the simulations.Simulation resultsdemonstrated that SOFFLFM improved the lateral and axial resolution by more than V2 and 2times in the second-and fourth-order accumulations,compared with that of FLFM.

Accurate 3D geometry measurement for non-cooperative spacecraft with an unfocused light-field camera

This work explores an alternative 3D geometry measurement method for non-cooperative spacecraft guiding navigation and proximity operations.From one snapshot of an unfocused light-field camera, the 3D point cloud of a non-cooperative spacecraft can be calculated from sub-aperture images with the epipolar plane image(EPI) based light-field rendering algorithm.A Chang'e-3 model(7.2 cm×5.6 cm×7.0 cm) is tested to validate the proposed technique.Three measurement distances(1.0 m, 1.2 m, 1.5 m) are considered to simulate different approaching stages.Measuring errors are quantified by comparing the light-field camera data with a high precision commercial laser scanner.The mean error distance for the three cases are 0.837 mm, 0.743 mm, and 0.973 mm respectively, indicating that the method can well reconstruct 3D geometry of a non-cooperative spacecraft with a densely distributed 3D point cloud and is thus promising in space-related missions.

Optimizing depth of field in 3D light-field display by analyzing and controlling light-beam divergence angle

A concept of divergence angle of light beams(DALB)is proposed to analyze the depth of field(DOF)of a 3D light-field display system.The mathematical model between DOF and DALB is established,and the conclusion that DOF and DALB are inversely proportional is drawn.To reduce DALB and generate clear depth perception,a triple composite aspheric lens structure with a viewing angle of 100°is designed and experimentally demonstrated.The DALB-constrained 3D light-field display system significantly improves the clarity of 3D images and also performs well in imaging at a 3D scene with a DOF over 30 cm.

Recent advances of light-field modulated operation in laser-induced breakdown spectroscopy

The simplicity and low-cost way to improve qualitative and quantitative analytical performance has always been a crucial concern for laser-induced breakdown spectroscopy(LIBS),and many scientists have been engaged in this evolving research direction.In this review,we investigated an update on recent developments in light-field modulated operation in LIBS.It covered a brief description of LIBS,optical polarization,and beam shaping.Here,the optical polarization is divided into laser beam polariza-tion and plasma polarization.In addition,the methodology and develop-ment of light-field modulated LIBS were summarized and discussed.Finally,the existing problems with light-field modulated LIBS were presented,along with some of their own insights and the future direction of their development.This review will provide a guideline for LIBS researchers with basic knowledge,which is very useful in the signal opti-mization of LIBS research and applications.

光场显微镜在神经光学成像领域的应用

通过对大脑中大体积神经元进行动态观测来学习神经元网络的感知、认知和复杂行为的机制是神经科学中的一个基本问题。光场显微镜(LFM)允许以视频帧速率进行三维成像,已成为对神经活动实时观测的一种技术选择。文章对光场显微镜目前的成像方法进行了综述,重点关注新型的算法。与传统的迭代重建方法相比,使用光场显微镜成像神经元活动要求开发新的基于深度学习的算法,充分利用嵌入在物理和光学模型中的先验,整合模型驱动和数据驱动的算法,增强算法的可解释性和泛化能力,实现快速稳健的光场显微镜成像。

超多视点显示中后向光线追踪的实时渲染方法

超多视点显示技术能够提供逼真的三维显示效果,但是大量视点图像的渲染合成过程使得三维显示的实时性受到极大的挑战。文章提出了一种超多视点显示中后向光线追踪的实时渲染方法,根据视点分配矩阵和子像素物理坐标,光线从视点位置出发逆向追踪到三维场景,并直接对视点合成图像进行子像素级别实时渲染。结果表明,在保证三维图像显示质量不变的情况下,随视点数目增加,渲染帧率始终保持在35FPS以上。该方法避免了渲染合成过程中的信息冗余,渲染速度相比传统的逐视点渲染方法提升了5个数量级。该方法为实现超多视点动态三维显示提供了新的途径。

Joint method for reconstructing three-dimensional temperature of flame using Lucy-Richardson and nearest neighbor filtering using light-field imaging

The real-time measurement and reconstruction of three-dimensional temperature are essential when studying the combustion process inside a flame. In the proposed sectioned flame light field imaging model, flame sections are reconstructed based on the characteristics identified using the Lucy-Richardson or nearest neighbor filtering methods, or a joint method involving a combination of both, to improve on the accuracy of two-dimensional temperature reconstruction. Compared to the results of a previous work, the proposed method increases the resolution in the depth of field direction and the extraction of the flame temperature of all sections from the same height ensures the accuracy of the reconstructed temperature distribution across the cross-section of the flame. The relative error when compared to the actual flame is less than 10%. Thus, this approach allows the accurate estimation of the three-dimensional temperature distribution inside a flame, and enables the rapid and effective reconstruction of the three-dimensional temperature field.

混凝土测试中数字图像相关方法最优光强研究

采用数字图像相关方法(DIC)测量混凝土结构表面应变场时,不同光强会引起图像灰度信息分布不同,进而影响DIC的测量结果。针对此问题,本文基于混凝土三点弯实验探究了不同光强对DIC测量精度的影响规律,并将实验结果与应变片数据对比。结果表明:平均灰度接近于截至区或饱和区时图像匹配失败。在光强可匹配的范围内,DIC的测量精度随平均灰度的增加先升高后降低,平均灰度190为最优光强。

单目三维视觉测量技术研究进展

单目三维视觉测量在视觉测量领域具有低成本、简便性、结构紧凑等优势,是以智能化、网络化制造为特征的先进制造典型技术之一。经过不断发展,单目三维视觉测量技术已成功应用于无人机导航、智能机器人、工业检测、医疗健康等领域,如今呈现出精准化、快捷化、微型化、自动化、动态化等发展趋势。以孔径数量为标准,将单目三维视觉测量技术分为单孔径及多孔径两大类,分别综述两类方法的研究现状和发展历程,重点论述了应用较广的运动恢复结构法(Structure From Motion,SFM)和光场三维测量方法,并对单目三维视觉测量技术的未来方向进行了展望。

联合空角信息的无参考光场图像质量评价

光场图像通过记录多个视点信息可为用户提供更加全面真实的视觉体验,但采集和可视化过程中引入的失真会严重影响其视觉质量。因此,如何有效地评价光场图像质量是一个巨大挑战。本文结合空间-角度特征和极平面信息提出了一种基于深度学习的无参考光场图像质量评价方法。首先,构建了空间-角度特征提取网络,通过多级连接以达到捕获多尺度语义信息的目的,并采用多尺度融合方式实现双重特征有效提取;其次,提出双向极平面图像特征学习网络,以有效评估光场图像角度一致性;最后,通过跨特征融合并线性回归输出图像质量分数。在三个通用数据集上的对比实验结果表明,所提出方法明显优于经典的2D图像和光场图像质量评价方法,其评价结果与主观评价结果的一致性更高。

海水环境光场水下辐照度测量光学设计

为了实现海洋环境光场水下辐照度测量光学设计,根据海洋辐射传输理论,对海洋环境下行辐照度、上行辐照度进行估算,完成海洋环境光场辐照度测量模块光学设计,并对其测量能力、姿态误差校正能力进行仿真分析,分析了探测器光敏面面积和透射窗口相对探测器的张角对测量能力的影响、横摇测量误差和纵倾测量误差对姿态测量误差影响,并得到横摇误差可采用动态水平法利用数据处理手段消除,纵倾测量误差可用对称排布的双辐照度探头测量模式消除的结论。海洋环境光场水下辐照度测量的光学设计,为水下实现目标环境光学特性测量奠定了技术支撑。

大视场白光干涉测量系统及性能研究

基于国产化的2倍迈克尔逊型干涉物镜组,优选配置0.5倍适配镜,对白光LED照明光源进行带通滤波参数的仿真估算和实验性能比较,构建了整套大视场白光干涉精密测量装置系统并进行了实验测试,通过白光干涉轴向响应实验曲线确定了中心波长。实验结果表明:通过光谱滤波获得了较为理想的白光干涉轴向响应曲线;系统的水平最大视场达到了14 mm;高度为2.04μm和20.43μm的标准台阶样品的测量结果分别为2.05μm和20.47μm,10次测量重复精度(标准差)分别为12 nm和16 nm。对粗糙度样板、微机电系统传感结构和半导体晶圆膜层进行了实测,表明所研制的系统装置在三维光学无损精密检测领域的应用具有可行性。

基于品牌思维的品牌营销模型构建与设计实践

目的在品牌化时代背景下,探索品牌传播范式的新变化,构建行之有效的品牌营销模型以指导企业品牌建设。方法从品牌思维视角,梳理品牌、消费者和企业之间的相互关系,分析传统品牌传播的局限和当代品牌需求。结合品牌设计实践案例,从四个阶段展开讨论:品牌光源阶段,解决品牌识别与认知问题;品牌光束阶段,解决品牌信息获取与传达问题;品牌光环阶段,解决品牌与消费者之间的沟通问题;品牌光场阶段,解决品牌终端认知问题。构建“品牌光场”营销模型,并以“蟹之家”品牌为例进行设计验证。结果“品牌光场”营销模型的建构和论证为企业的品牌建设提供了一种更形象、更直接的设计营销方法。结论通过品牌光场营销模型,企业品牌可以更好地自我识别和定位,提高信息触达和消费者沟通效率,并增强终端感知,实现品牌复利。

空间相干结构光场产生、传输及应用研究进展

空间相干性是光场除了振幅、相位和偏振以外的一个固有属性,它在理解光的干涉、传输、光与物质相互作用等方面起着重要作用.近年来,对空间相干性的研究已经逐渐拓展至对空间相干结构的构建及特性研究,这是因为具有特定空间相干结构分布的光场展现出了新奇的物理效应,如自聚焦、自分裂、自偏移和自整形传输特性等.这些新奇物理效应的许多潜在应用也逐渐被发现,包括在自由空间光通信中降低大气湍流的负面效应、基于空间相干结构的光学加密和鲁棒光信息传输、光学微粒俘获及操纵等.本综述系统地回顾空间相干结构光场的表征方法、理论构建和实验产生方法、在自由空间和湍流介质中的传输特性和相关应用.首先,利用非负正定条件和相干模式分解理论来表示空间相干结构光场的交叉谱密度函数;然后,讨论理论和实验上构建及产生空间相干结构光场的2种不同策略,一种是基于广义范西特-泽尼克定理,另一种是基于相干模分解理论;接下来,概述特定空间相干结构光束在自由空间和湍流大气中的新颖物理特性;最后,介绍空间相干结构光场在降低大气湍流负面效应、光学加密、复杂介质中的鲁棒光信息传输和光学微粒俘获和操纵等方面的应用.光学空间相干结构不仅为光操控提供了新的自由度,产生的空间相干结构光场在诸多领域也展现出了重要应用价值.

孟子的古典管理数学思想

孟子善论辩,而为了明晰事理,他在论辩过程中经常会给出一些算术问题。因此,《孟子》一书包含着比较丰富的古典管理数学内容,如“万取千焉,千取百焉”的利益观,“请野九一而助,国中什一使自赋”的井田制构想,以及“今滕,绝长补短,将五十里”的几何割补方法等。特别是孟子将“规矩”“六律”和“仁政”三者统一起来,强调把数学置于王道之国的基础地位,重视数学在社会政治领域的应用,主张“苟求其故”的数学思维(包括数学原理和数学方法),特点非常突出。这既反映了春秋战国古典数学发展的特点,同时又是对《周礼》“九数”之艺的进一步总结和提高。

医用光学内窥镜覆盖全视场范围的边缘光效评价方法

该研究阐述了行业标准YY 0068.1-2008《医用内窥镜硬性内窥镜第1部分:光学性能及测试方法》对边缘光效的基本评价思路,通过以特定的实际内窥镜数据为例分析相对视场位置的边缘光效评价结果与绝对视场位置的边缘光效评价结果相反的情况,指出仅由YY 0068.1-2008规定的90%最大入瞳视场角(W_(p))处相对视场位置评价边缘光效不全面,需补充建立覆盖全视场范围的绝对视场位置边缘光效的评价方法;同时,基于YY 0068.1-2008的基本评价思路建立了覆盖全视场范围的边缘光效评价方法,旨在为行业标准的进一步修订和完善提供参考。

一种基于FPGA的FTN-VLC系统设计与测试

为了提升可见光通信(VLC)系统的传输速率和频谱利用率,设计了一种基于现场可编程门阵列(FPGA)超奈奎斯特(FTN)-VLC系统。该系统主要由FPGA、数/模(D/A)转换器、低通滤波器、雪崩二极管、电流/电压(I/V)转换器和电压比较器组成。对系统的软件和硬件进行了仿真分析和性能测试。仿真与测试结果表明:当传输距离为0.5 m时,系统的数据传输速率可达10 Mb/s,频谱利用率较同等条件下的奈奎斯特光通信系统提升了18.25%。

超表面的矢量光场调控

矢量光场由于其独特的光场分布特性,在许多领域都得到了广泛且深入的研究与应用。传统光场调控手段受限于材料的光学特性及物理尺寸,难以实现灵活高效的动态操控功能。超表面凭借其亚波长结构设计所带来的额外自由度,突破了上述局限,使得对矢量光场的振幅、相位、偏振态乃至传播方向等的独立调控成为可能。本文结合国内外矢量光场领域的基础理论及最新进展,系统地阐述了矢量光场的基本原理及其数学模型,重点介绍了目前超表面生成矢量光场的方法,以及这种矢量光场在聚焦、轨道角动量检测、高精度定位等方面应用的具体案例与创新成果。