Three-dimensional color particle image velocimetry based on a cross-correlation and optical flow method

Rainbow particle image velocimetry(PIV)can restore the three-dimensional velocity field of particles with a single camera;however,it requires a relatively long time to complete the reconstruction.This paper proposes a hybrid algorithm that combines the fast Fourier transform(FFT)based co-correlation algorithm and the Horn–Schunck(HS)optical flow pyramid iterative algorithm to increase the reconstruction speed.The Rankine vortex simulation experiment was performed,in which the particle velocity field was reconstructed using the proposed algorithm and the rainbow PIV method.The average endpoint error and average angular error of the proposed algorithm were roughly the same as those of the rainbow PIV algorithm;nevertheless,the reconstruction time was 20%shorter.Furthermore,the effect of velocity magnitude and particle density on the reconstruction results was analyzed.In the end,the performance of the proposed algorithm was verified using real experimental single-vortex and double-vortex datasets,from which a similar particle velocity field was obtained compared with the rainbow PIV algorithm.The results show that the reconstruction speed of the proposed hybrid algorithm is approximately 25%faster than that of the rainbow PIV algorithm.

Simulation of distributed optical fiber disturbance detection system based on Sagnac/Mach-Zehnder interferometer and cross-correlation location

A distributed optical fiber disturbance detection system consisted of a Sagnac interferometer and a Mach-Zehnder interferometer is demonstrated. Two interferometers outputs are connected to an electric band-pass filter via a detector respectively. The central frequencies of the two filters are selected adaptively according to the disturbance frequency. The disturbance frequency is obtained by either frequency spectrum of the two interferometers outputs. An alarm is given out only when the Sagnac interferometer output is changed. A disturbance position is determined by calculating a time difference with a cross-correlation method between the filter output connected to the Sagnac interferometer and derivative of the filter output connected to the Mach-Zehnder interferometer. The frequency spectrum, derivative and cross-correlation are obtained by a signal processing system. Theory analysis and simulation results are presented. They show that the system structure and location method are effective, accurate, and immune to environmental variations.

Load Balancing in WDM Optical Networks with and without Wavelength-Continuity Constraints

In practical optical networks, there is often the same number of wavelengths in a fiber. But if it is not carefully designed, there will be much difference in link load among different fibers, and unnecessary wavelengths will be needed. This paper investigated this load balancing issues to minimize the wavelength requirements. Both Integer Linear Programming (ILP) and heuristic algorithms were presented to solve such a problem in WDM optical networks with or without wavelength continuity constraints.

Optimal Algorithms for Load Balancing in Optical Burst Switching Networks

Data packet drop can happen in Optical Burst-Switched(OBS)when two data bursts are competing on the same wavelength.Recently,many techniques have been developed to solve this problem but they do not consider the congestion.Also,it is necessary to balance the load system in the OBS network.The Ant Colony Optimization(ACO)technique can be applied to determine the straight and the safest route.However,the ACO technique raises both power utilization as well as the execution time.In this study,Cuckoo Search(CS)and ACO methods based approach is proposed to avoid the congestion and load balancing in the OBS network.This strategy evaluates the intensity of hotspot data and then launches the congestion rate optimization process that depends on their load situations.The congestion rate optimization represents the available bandwidth,data distribution rate,queue size,and access rate,and also these factors are optimized through the CS technique.The fitness utility in the CS technique adjusts the distribution rate in the OBS network,and the proposed ACO technique solves the energy utilization problem.The simulation results proved that the presented strategy evades both the end-to-end delay as well as the possibility of packet drop.

Simulation Analysis of Balance Detection Technique in Coherent Optical Receiver

This paper introduces the working principle of the balanced heterodyne detection system, establishes the corresponding mathematical model, deduces the signal to noise ratio (SNR) formula of the balanced heterodyne detection. By comparing balance heterodyne detection with general coherent detection with MATLAB numerical simulation, the superiority of balance heterodyne detection system is proved theoretically. Finally, the simulation models of ordinary heterodyne detection, balance detection and double balance detection system are built by OptiSystem. The simulation results are consistent with the conclusions derived from the mathematical analysis, which provides a new method for the research of weak laser detection technology.

A comparison of cross-correlation-based and phasecorrelation-based image registration algorithms for optical coherence tomographic angiography

A large field of view is in high demand for disease diagnosis in clinical applications of optical coherence tomography(OCT)and OCT angiography(OCTA)imaging.Due to limits on the optical scanning range,the scanning speed,or the data processing speed,only a relatively small region could be acquired and processed for most of the current clinical OCT systems at one time and could generate a mosaic image of multiple adjacent small-region images with registration algorithms for disease analysis.In this work,we investigated performing cross-correlation(instead of phase-correlation)in the workflow of the Fourier–Mellin transform(FMT)method(called dual-cross-correlation-based translation and rotation registration,DCCTRR)for calculating translation and orientation offsets and compared its performance to the FMT method used on OCTA images alignment.Both phantom and in vivo experiments were implemented for comparisons,and the results quantitatively demonstrate that DCCTRR can align OCTA images with a lower overlap rate,which could improve the scanning efficiency of large-scale imaging in clinical applications.

光流结合特征提取的室内机器人避障技术研究

为解决室内机器人正向准确避障问题,提出一种光流结合特征提取的视觉避障方法。将LK光流与多尺度思想结合,加入仿射变换,提高算法追踪角点的噪声鲁棒性,进而准确检测视场中的障碍物;通过评估障碍物风险程度,制定出碰撞时间(TTC)结合光流平衡策略的碰撞机制,引导机器人在无碰路径上移动。改进光流与特征提取结合能提高相机快速运动下的追踪成功率,制定的碰撞策略能够有效规避机器人前方的障碍物。实验表明,相机快速运动时,算法能提高追踪的准确性,有效检测出视场中的障碍物,引导机器人无碰撞行驶,具备较强的独立性和实时性。

基于组合热流模拟策略的遥感卫星热平衡试验设计与验证

针对某型遥感卫星的不同区域对高精度热流模拟的需求,文章提出一种组合热流模拟策略:以红外加热笼来实现卫星舱板表面的外热流模拟,用薄膜电加热器实现卫星外露复杂表面外热流模拟。试验结果表明,在文述参试卫星状态及所采取的热设计措施下,该方法可对卫星低温初期、高温末期和高温热真空工况下的外热流进行精准模拟,并可有效考核遥感卫星的热控设计。该热流模拟策略可为卫星瞬态功耗散热设计的优化提供参考依据,为我国未来光学遥感卫星的热平衡试验及验证提供技术支撑。

“巴遥一号”卫星双相机热设计及验证

针对“巴遥一号”卫星相机主体全寿命周期内温度应保持较高稳定性和均匀性的任务要求。通过建立热阻网络模型,分析热控设计的重点和难点,并提出有效管理热量传递和合理设计控温方式的方法;利用结构热控一体化设计解决双相机焦面电路高功率密度热量排散问题,采用直接与间接相结合的控温方式提高主光学结构温度稳定性。通过热仿真分析和热平衡试验验证热设计的准确性。相机入轨4年后1个月内的在轨温度变化显示,相机各部分温度水平和温度稳定性满足设计指标要求,镜头的温度波动范围在0.09~0.17℃,CCD的温度波动范围在0.93~4.30℃,表明相机热控设计合理有效。以上设计实践可为双相机一体化热控设计提供借鉴。

液体分频介质的制备及其对光伏/热系统的影响分析

光谱分频光伏/热(PV/T)复合利用技术打破了PV电池低工作温度与其高品位热需求的冲突,实现了高效的光电效率和热效率。为了制备合适的选择性分频介质实现PV/T器件内能量合理分配,以去离子水为基液,利用贵金属Ag纳米颗粒与无机CoSO_(4)组合实现分频液体光学特性的高效调控。此外,基于能量平衡法建立了典型PV/T原型系统的电、热输出模型,分析了分频介质光学调控前后对系统热电输出特性。结果表明,水基分频液具有高效红外吸收特性,加入Ag纳米颗粒后,分频介质在可见光波段出现了明显的吸收峰,峰值为435 nm。进一步加入CoSO_(4)后,可以拓展纳米流体吸收峰宽度,且在红外也具有一定的吸收强化。对比光学调控前后分频介质对PV/T系统热电性能影响可以看出,分频介质总的吸收特性增加,PV/T系统的热效率呈现增加的趋势,但其电效率有所下降。基于液体分频PV/T系统的总[火用]效率亦随之增加,且超过28%。分频介质光学特性高效调控可实现PV/T系统的内能量的可控分配。

多基色显示系统基色亮度求解及讨论

为了进一步提升显示系统的颜色显示能力,并解决三基色显示系统理论对多基色显示系统不兼容的问题,采用参数不等式的方法进行了理论分析,基于多基色显示系统和三基色显示系统的差异,求解出多基色显示系统的峰值亮度所对应的解空间,从理论上推导了多基色显示系统中基色峰值亮度的设置,并对解空间的等价性和完备性进行了模拟实验验证。结果表明,四基色、五基色和六基色激光显示系统对应的理论最大色域体积分别是2185100,2258400和2395800。该方案对多基色显示系统的理论模拟具有重要的指导意义。

基于T型三相电弧的光纤熔接系统设计

针对各种直径光纤的熔接需求,实现大直径光纤熔接和拉锥、小直径光纤快速熔接的目的,该系统采用启明星ZYNQ开发板作为主控,使用Verilog语言和Vivado软件编写并下载固定范围频率且占空比可调的PWM信号,通过ADS1256芯片采集电路中电流大小,进而对PWM信号占空比进行实时调整,使电极放电的电流强度维持在一个比较稳定的状态,从而构成了光纤熔接机的放电子系统。通过重复进行放电实验,得出在50%和40%占空比Boost升压、相位相差三分之一的PWM信号控制下,系统放电电弧相对均匀,且熔接效果最好。

基于双Cuk电路电池主动均衡系统的控制与优化

针对新能源电池间电压不均衡现象,采用了一种基于非隔离式主动均衡闭环自适应调节的控制均衡方法。使用意法半导体STM32F407VET6作为主控与BMS上位机和车机进行交互;使用上海琪埔维半导体提供的XL8812车规级芯片作为电压采集芯片。该方案已打板测试,实现了4~240节电池电压测量,以12节电池为一组可以进行主动均衡。主控输出两路互补带死区频率和占空比均可调节的双路PWM信号,通过光隔离放大来驱动均衡电路。得出“削峰填谷”的策略,成功地将电压较高的电量转移到电压较低的电池单体中。

大孔径太赫兹波成像光学系统设计

太赫兹波具有高穿透性、低能性及指纹谱性等特征,被广泛应用于探测领域,因此,设计太赫兹波成像光学系统具有重要的意义和广泛的应用前景。首先,以四块透镜构成的天塞物镜为参考结构,应用近轴光学系统像差理论构建系统像差平衡方程,给出了系统初始结构参数求解函数和方法,再结合光学设计软件进一步校正系统像差,最终设计了一种用于太赫兹波探测的大孔径光学成像系统。该光学系统由4块同轴折射透镜构成,焦距为70 mm,F数为1.4,全视场角为8°,在奈奎斯特频率10 lp/mm处全视场角范围内的调制传递函数(MTF)值均大于0.32,各视场内的弥散斑均方根(RMS)半径均小于艾里斑半径。最后对系统各种公差进行分析和讨论。设计结果表明,本文设计的太赫兹波探测光学成像系统具有孔径大、结构简单且紧凑、成像质量较好且加工性易于实现等特点,满足设计要求,它在太赫兹波段高分辨率探测领域具有重要应用价值。

基于植被光学厚度的全球植被动态监测进展

植被光学厚度(vegetation optical depth,VOD)为一种基于微波的植被含水量和生物量估算方法。与光学遥感相比,卫星VOD对大气扰动的敏感性较低,可测量植被不同方面的特征和信息,为全球植被监测提供了一个独立和互补的数据源,已经被广泛用于研究全球气候和环境变化对植被的影响。了解目前VOD在全球植被动态监测的应用研究进展,对其进一步发展和深入应用非常重要。鉴于此,文章首先重点介绍了被动微波和主动微波反演VOD的主要方法,对比分析不同传感器VOD产品的主要特点;然后,从植被特征监测(如植被含水量、生物量)、碳平衡分析、干旱监测、物候分析等方面总结当前VOD在植被动态监测应用方面的研究进展;最后,探讨了VOD产品的优缺点和改进方法,进一步展望了VOD技术在植被动态监测中的应用前景。

外观融合运动感知的运动目标分割算法

现实场景中的运动目标分割旨在分割当前场景下的运动物体,对于许多计算机视觉应用有着至关重要的作用。现有的运动目标分割算法大多通过2D光流图中的运动信息来分割运动物体,然而,这些方法还存在一些问题。当运动物体在极面内运动或者其3D运动方向和背景一致时,很难通过光流图分割得到;另外,错误的光流预测也会影响分割的结果。为了解决以上问题,提出了不同的运动代价,以提升运动目标分割的正确率。针对和背景共线或共面运动的物体,设计均衡重投影代价和多角度光流对比代价,通过运动物体的2D光流与背景2D光流的差异来检测运动物体。针对自我运动退化,设计差异单应性代价。最后,提出了一种基于外观融合的运动感知结构,以分割各种场景下的运动物体。采用多模态共同注意力门控,更有效地捕获运动特征和外观特征的关系,以促进外观特征和运动特征更好地交互。此外,为了突出运动的物体,提出了多层运动注意力模块,以减少冗余的外观特征对结果的影响。实验结果表明,所提方法在KITTI,JNU-UISEE,KittiMoSeg和Davis-2016数据集上均能获得较优的运动目标分割结果。

Generation of ultra-flat optical frequency comb using a balanced driven dual parallel Mach–Zehnder modulator

We propose and experimentally demonstrate an ultra-fiat optical frequency comb （OFC） generator by a bal- anced driven dual parallel Mach-Zehnder modulator. Five- and seven-tone OFC with exactly equal intensity can be generated theoretically, Experimentally obtained five- and seven-tone OFC with flatness of 0.6 and 1.26 dB are demonstrated, respectively, which agrees well with the theoretical results.

基于资源频谱的光纤网络带宽自动适配方法

通过对光纤网络带宽优化适配调节,提高网络的资源分配均衡性,提出基于资源频谱的光纤网络带宽自动适配方法。根据优先级业务调度方法建立光纤网络带适配的SDN(Software Defined Network)网络构架体系,通过对网络设备的控制与转发功能调节,采用带宽保障机制进行光纤网络业务流量的均衡配置,采用资源频谱的延迟调度方法,进行光纤网络资源频谱的多业务分级管理。为保障各类不同业务带宽需求,采用高能的物理计算系统结构进行光纤网络带宽的资源频谱均衡配置,实现对光纤网络的存储资源、系统资源、频谱资源的分类管理和适应性配置。测试表明,该方法有效降低了光纤网络带宽分配的延迟,提高了网络带宽利用率,无论是网络的读取和写入性能都有较大提升。

经鼻内镜内下壁减压术治疗Graves眼病压迫性视神经病变的效果

目的 探讨经鼻内镜内下壁减压术治疗Graves眼病压迫性视神经病变的临床效果。方法 选取医院2017年1月至2022年6月收治的92例Graves眼病压迫性视神经病变患者,根据随机数字表法分为研究组和常规组,各46例。研究组接受经鼻内镜内下壁减压术,常规组接受眼眶平衡减压术,比较两组治疗前后眼球突出度及视力变化情况、术中出血量和手术时间、生活质量,比较两组并发症发生情况。结果 治疗后,两组眼球突出度较治疗前下降,且研究组低于常规组(P<0.05),两组最佳矫正视力均上升,且研究组高于常规组(P<0.05)。研究组术中出血量少于常规组,手术时间短于常规组(P<0.05)。治疗后研究组社会功能、认知功能、心理状态、健康状态评分和总分均高于常规组(P<0.05)。两组并发症总发生率比较差异无统计学意义(P>0.05)。结论 经鼻内镜内下壁减压术治疗Graves眼病压迫性视神经病变可以缓解患者眼球突出问题,帮助患者更好恢复视力,减少术中出血量并缩短手术时间,提高生活质量,且安全性高。