Significance Internet of Things(IoT)technology is an important part of the new generation of information technology.The IoT is a huge network formed by combining various information devices and sensors.This huge network is based on various types of sensors,and the sensor,as a bridge between the physical world and the digital world,is an integral part of the IoT architecture.Distributed fiber-optic sensing(DFOS)technology is widely used in many fields because of its long-distance,large-range,high-precision,and multi-point measurement capabilities. However,most of the DFOS sensing systems use a single scattering mechanism.The parameters measured by a single scattering mechanism are limited,so it fails to fully and accurately reflect the real state of the measured object,and it is difficult to fully and effectively meet the needs of health monitoring or automatic control.In order to solve the problem that the conventional DFOS system only uses a single scattering mechanism,researchers have proposed a series of DFOS sensing systems with multi-mechanism in recent years,using the same system to measure multiple parameters.In this paper,the multi-mechanism DFOS technology developed in recent years is reviewed,and the different multi-mechanism DFOS systems and their performances are classified from the perspective of different scattering mechanisms(Table 1). Progress There are three kinds of scattering in optical fibers,namely Rayleigh scattering,Brillouin scattering,and Raman scattering.DFOS systems that use only one of these scattering mechanisms measure limited parameters.The multi-mechanism DFOS systems can measure more parameters by using multiple scattering mechanisms in one system,so as to reflect the state of the measured object more comprehensively. The multi-mechanism DFOS systems are divided into five categories according to the sensing mechanism used.The system combining Rayleigh scattering with Brillouin scattering can be used not only to measure temperature,strain,and vibration but also to separate the response of temperature and strain.Systems that combine Rayleigh scattering with Raman scattering can be used for sensing temperature and vibration events.Systems that combine Brillouin scattering with Raman scattering are generally used to separate system responses due to temperature and strain. The methods of combining scattering mechanisms in the systems are different.In this paper,these combination methods are divided into two categories:the combination based on multiplexing(wavelength division multiplexing,space division multiplexing,and time division multiplexing)and the combination of different scattered light generated by the same probe light.Multiplexing-based combination methods are straightforward in principle,but complex systems often require special sensing fibers or sacrifice measurement speed.The system using different scattered light of the same probe light has a simple setup,but special modulation and demodulation schemes are required.In addition,there may be an influence between different scattering mechanisms when the different scattering of the same probe light is used in the same system. In addition to the combination of different kinds of scattered light in optical fibers,we also enumerate distributed sensing systems using scattered light and single point optical fiber sensing systems using interference structures or gratings.Compared with distributed sensing systems,single-point optical fiber sensing systems have the advantages of high precision and large measurement range,but the number of measured points is limited,and special optical fiber structures(such as fiber grating)are required.In practical applications,distributed fiber optic sensors or single-point fiber optic sensors can be flexibly selected according to different scenario requirements. Conclusions and Prospects Finally,the prospect of multi-mechanism DFOS technology is provided.With the increasing demand for large-scale sensing and monitoring,researchers have proposed more and more multi-mechanism DFOS systems to measure more parameters and improve sensing performance.The future development of multi-mechanism DFOS systems should focus on the aspects of system complexity,sensing performance,data processing,and practical applications. One of the natural advantages of multi-mechanism DFOS systems is the multiplexing of components in a sensor system with different mechanisms,which can significantly reduce the cost of the system when multiple sensing functions are implemented.The data processing method expands the application scenarios,increases the functions of the system,and improves the performance of the system without increasing the complexity and cost of the system hardware.Finally,how to deeply integrate the multi-mechanism DFOS systems with practical applications is an important direction.In order to achieve this direction,the design of the sensor system,the layout of the sensor cable,and the use of multi-sensor information should be considered and designed.
With the development of display devices towards high resolution and high refresh rate, the amount of video image data is increasing exponentially, which brings challenges to the bandwidth resources of the display system. From the perspective of human visual system, combining the change of the gaze point position and the sampling characteristics of the human eye foveal, an adaptive foveal image transmission algorithm based on human eye gaze point is proposed to reduce the data transmission bandwidth. The experimental results show when the viewing distance is 2 and the gaze point position is at the center of the image. The comprehensive compression ratio is 12.257, the data transmission clock frequency is 12.532MHz, and the total amount of data transmitted is 8.158% of the original total. The total amount of data transmission is greatly reduced, and the pressure on data transmission bandwidth is effectively relieved. So that video images with higher resolution and refresh rate can be displayed under the same clock frequency.
为提升机载紫外告警传感器性能,设计了一款基于ICMOS构架的紫外告警传感器.该型传感器工作波长覆盖250～270 nm,可通过RS422接口上传告警目标信息,具有超广角、高角分辨率、灵敏度高、重量轻、功耗低等优点.对传感器的技术指标、工作原理和设计构架等方面进行了介绍.完成了传感器的基本功能、性能测试,经环境试验验证,满足机载使用要求.
为了克服红外光与白光成像机理不同引起的图像信息无法同步、无法同时使用红白光双光谱系统实现测距的问题,以待测目标的边界作共性特征,采用红白光相机对同一目标的共性特征进行采集,将采集到的图像通过高斯算子进行平滑处理,再运用Laplace扩展算子进行边界特征检测,将不同距离下目标边界像素位置数据进行线性拟合并建立测距误差模型,从而生成边界特征匹配算法.研究结果表明边界特征匹配算法可以使红白光双目系统克服成像机理不同这一问题实现测距功能,测距范围可达到40 m,最大相对误差是0.975％.
针对目标检测对实时性要求越来越高的情况,提出了一种基于现场可编程门阵列(Field Programmable Gate Array,FPGA)实现的多运动目标检测算法.该方法通过帧差法提取运动目标,然后基于距离阈值对形态学处理后的图像进行目标分割,最后对运动目标标记显示.系统通过CMOS摄像头采集视频,采用FPGA平台外接DDR3高速大容量缓存,实现了视频图像的采集、存储、目标检测和显示.实验结果表明,提出的多目标检测系统能够有效的实时检测出多个运动目标,并且在分辨率为1 024×600的情况下帧率达到38 fps.
为提高矢量光场显示亮度和视角均匀性,提出了一种应用于圆偏振光场成像的超构光栅结构.利用严格耦合波分析,逐像素对超构光栅结构进行仿真,研究了入射光偏振状态、光栅结构、入射角度对-1级光衍射效率的影响规律.仿真结果表明,圆偏振光显示可以使得光栅衍射效率稳定高效,当光栅周期为500 nm时,与基于TE和TM设计的光栅结构相比,圆偏振光设计的光栅结构衍射效率提高了 18.5％和2.6％;光栅高度和占空比对衍射效率具有明显的影响.综合考虑光栅制备难度、衍射效率和视角均匀性,设计了一种高度为0.6 μm,占空比为0.4的光栅阵列结构应用于圆偏振光场显示,系统衍射效率可以达到40％以上,具有较优的综合性能,对超构光栅设计制备和裸眼3D显示具有一定指导意义.
基于硅基铌酸锂薄膜(Lithium Niobate on insulator,LNOI)材料平台,设计并制备了高速电光开关芯片,并实现了芯片的光纤耦合、管壳封装和性能测试.测试结果表明,该高速电光开关器件的开关速度达到13.4ns,消光比达到31.8 dB.研究工作对未来研制光学延时芯片和波束形成网络芯片具有重要的支撑意义.
利用自研的Φ-OTDR系统,在福建省某海上风电场开展了演示验证,实现了对海风机机组的启动-运行-停机等不同工况下的状态分析与诊断,总结了不同工况下的振动特征及诊断依据;以及针对海底电缆的水流冲击、锚害拖拽、抵近船只航行等监测预警功能,总结了不同海缆状态下及周边环境感知目标事件特征.实测结果证明该方案能够在线监测海风机与海底电缆状态,并有效感知周围环境,为提升海上风电场运维水平提供了可靠的技术途径.
基于扩展标量衍射理论,建立了衍射光学元件的微结构高度与周期宽度和入射角度的理论关系模型,提出了不同入射角度时,利用带宽积分平均衍射效率最大化实现设计波长和微结构高度等结构参数的优化设计方法.以工作在近红外波段的衍射光学元件为例进行分析.结果表明:周期宽度一定时,入射角度的改变会引起基于带宽积分平均衍射效率最大化所确定的结构参数发生变化.该设计方法和结论可以用于指导衍射光学元件的设计.
深入分析了铜钛刻蚀液的刻蚀机理,并对刻蚀液浓度的变化进行实验分析.在此基础上,通过实验完成了铜钛刻蚀液浓度变化模型曲线的研发,并提出了进行浓度控制的方法,实现了铜钛刻蚀液的稳定应用并极大地提高刻蚀液的使用寿命.研究为相关领域的生产和研发提供了一定的参考.
以共轭涡旋光干涉原理为基础,理论分析了干涉图像旋转角度和位移量的对应关系,利用光学仿真系统验证了理论的可行性.采用基于空间光调制器和改进型的马赫-泽德干涉仪组成的共轭涡旋光干涉测量系统,利用不同拓扑荷数的共轭涡旋光实验测量了纳米位移台的位移变化.实验结果表明,在位移量为100nm、200nm和250nm的情况下,拓扑荷数为3时的相对误差最小,分别为2.19％、1.28％和1.27％.研究结果有助于提高基于共轭涡旋光干涉位移测量的精度.
对基于混合波束赋形的系统架构进行了研究.提出了新型的混合波束赋形架构,并采用高集成宽带收发芯片AD9361与全可编程片上系统进行多通道数字中频系统的搭建.测试结果表明该方案稳定可靠,满足大带宽高速传输的需求.
提出了一种基于深层特征嵌入的高分辨率人脸图像重建方法,利用预训练的Style-GAN2生成对抗网络模型作为人脸图像生成器,并将深层特征嵌入到StyleGAN2的W+空间中,通过梯度下降法优化w+向量,并将优化后的w+向量输入到StyleGAN2中生成分辨率为1 024×1 024的重建人脸图像.实验结果表明,重建图像与对应真实人脸图像不仅在视觉上有着较高的相似性,且在同一特征提取网络下,LFW和ColorFeret数据集的重建图像在FAR为0.1％时Ⅱ型评估TAR分别为96.04％和100.00％,并且在两种不同的活体检测程序下的通过率分别达到了88.67％和74.67％.所提方法在实现重建高分辨率人脸图像的同时,与真实人脸图像的特征相似度方面也表现优秀.
采用硅基金属整片键合后选择性去衬底技术,通过热压键合技术将(100)晶面硅与(111)晶面硅高温键合,利用聚二甲基硅氧烷保护(100)晶面硅衬底,再粗化(111)晶面硅衬底加快其刻蚀速率,后通过湿法选择性刻蚀去除(111)晶面硅衬底.此技术在不损伤硅基驱动芯片的前提下实现了选择性去除硅基氮化镓外延衬底,是一种材料混合集成的新技术,有望应用于自对准硅基Micro-LED微显示器件制程和光电子器件集成领域.
大功率LED车灯采用风扇进行强制对流散热,针对风扇周边空间尺寸影响车灯散热性能的问题,采用有限元仿真、均匀设计法及响应面分析相结合的研究方法进行优化研究.首先,利用有限元软件FIoEFD研究了风扇护风罩与壁面的径向距离A、风扇入风口与壁面的距离B及风扇出风口与散热器的距离C三个设计参数对大功率LED车灯风冷散热系统散热性能的影响;然后,使用均匀设计法设计试验方案进行响应面分析并拟合出三个参数与LED焊点温度之间的回归模型,利用Pareto分析法确定三个参数对系统散热性能的影响大小;最后,利用Minitab软件的响应优化器,以LED结温最小化为目标,确认三个参数的最佳组合是A为8.4 mm、B为16.3 mm、C为4.3 mm.通过对最佳组合进行实验,表明此组合具有最优的散热性能,同时仿真和实验结果具有一致性,验证了仿真的可靠性.
提出了一种在大气氛围和低温条件下实现Au-Au薄膜的金属键合技术,研究了不同表面活化处理时间对Au-Au薄膜表面粗糙度、Au-Au薄膜的键合质量和可靠性的影响.实验结果表明,Au薄膜表面粗糙度随着表面活化处理时间的增加先减少后增大,当表面活化处理时间为20 min时,Au薄膜表面粗糙度均方根为6.9 nm,悬挂键数量和粗糙度达到一个相对平衡的关系,Au-Au薄膜键合后的平均剪切强度为131.8 MPa,最大剪切强度高达159.1 MPa.因此,Au薄膜表面理想的表面活化处理时间可有效地提高Au-Au薄膜键合质量和稳定性,为实现混合集成Micro-LED器件的低温金属键合提供理论指导.
