Ultrafast pulse-dilation framing camera and its application for time-resolved X-ray diagnostic

An ultrafast framing camera with a pulse-dilation device,a microchannel plate(MCP)imager,and an electronic imaging system were reported.The camera achieved a temporal resolution of 10 ps by using a pulse-dilation device and gated MCP imager,and a spatial resolution of 100μm by using an electronic imaging system comprising combined magnetic lenses.The spatial resolution characteristics of the camera were studied both theoretically and experimentally.The results showed that the camera with combined magnetic lenses reduced the field curvature and acquired a larger working area.A working area with a diameter of 53 mm was created by applying four magnetic lenses to the camera.Furthermore,the camera was used to detect the X-rays produced by the laser-targeting device.The diagnostic results indicated that the width of the X-ray pulse was approximately 18 ps.

Neutronic analysis of ITER radial x-ray camera

The radial x-ray camera(RXC) is designed to measure the poloidal profile of plasma x-ray emission with high spatial and temporal resolution. The RXC diagnostic system consists of internal camera module and external camera module that view the core region and outer region through the vertical slots of the diagnostic first wall and diagnostics shield module of the equatorial port plug. To ensure the normal performance of the silicon photodiode array detectors of the cameras in the hard neutron irradiation environment in ITER tokamak, it is necessary to calculate neutron flux, radiation damage and the nuclear heating of the silicon photodiode array detectors and simulate the radiation maps of the range of RXC. This work estimated the nuclear environment of RXC based on Monte Carlo N-particle transport code, plasma scenarios of ITER tokamak and the RXC-integrated ITER CLITE model. The neutron flux of silicon photodiode array detectors and the lifetime of the silicon photodiode detector in the camera were calculated. The neutronic analysis results show that the shielding design has achieved the effect as expected and is able to guarantee the normal work of the detector during the ITER deuterium–deuterium phase without replacement, three detectors of the external camera can be operated during the whole deuterium–tritium phase without replacement.

Spatial resolution and image processing for pinhole camera-based X-ray fluorescence imaging: a simulation study

Spatial resolution and image-processing methods for full-field X-ray fluorescence(FF-XRF)imaging using X-ray pinhole cameras were studied using Geant4simulations with different geometries and algorithms for image reconstruction.The main objectives were:(1)calculating the quantum efficiency curves of specific cameras,(2)studying the relationships between the spatial resolution and the pinhole diameter,magnification,and camera binning value,and(3)comparing image-processing methods for pinhole camera systems.Several results were obtained using a point and plane source as the X-ray fluorescence emitter and an array of 100×100 silicon pixel detectors as the X-ray camera.The quantum efficiency of a back-illuminated deep depletion(BI-DD)structure was above 30%for the XRF energies in the 0.8–9 keV range,with the maximum of 93.7%at 4 keV.The best spatial resolution of the pinhole camera was 24.7μm and 31.3 lp/mm when measured using the profile function of the point source,with the diameter of 20μm,magnification of 3.16,and camera bin of 1.A blind deconvolution algorithm with Gaussian filtering performed better than the Wiener filter and Richardson iterative methods on FF-XRF images,with the signal-to-noise ratio of 7.81 dB and improved signalto-noise ratio of 7.24 dB at the diameter of 120μm,magnification of 1.0,and camera bin of 1.

Enhancement of Frame-rate Using Digital Camera

Frame rate is corresponding to the temporal resolution and the number of the pixels of the picture is corresponding to the spatial resolution. They are both very important for the researchers. The ideal image analysis and processing system should have high spatiotemporal characteristics, which is much expensive in practical use. A new method to enhance dynamic frame rate using multi-digital camera(DC) is proposed and the result shows that it could increase the frame rate effectively and decreases the cost in practical use.

Ultrafast two-dimensional x-ray imager with temporal fiducial pulses for laser-produced plasmas

It is challenging to make an ultrafast diagnosis of the temporal evolution of small and short-lived plasma in two dimensions. To overcome this difficulty, we have developed a well-timed diagnostic utilizing an x-ray streak camera equipped with a row of multi-pinhole arrays. By processing multiple sets of one-dimensional streaked image data acquired from various pinholes, we are capable of reconstructing high-resolution two-dimensional images with a temporal resolution of 38 ps and a spatial resolution of 18 μm. The temporal fiducial pulses accessed from external sources can advance the precise timing and accurately determine the arrival time of the laser. Moreover, it can correct the nonlinear sweeping speed of the streak camera. The effectiveness of this diagnostic has been successfully verified at the Shenguang-II laser facility,providing an indispensable tool for observing complex physical phenomena, such as the implosion process of laser-fusion experiments.

大电流脉冲发生器设计及应用

长磁透镜是展宽型分幅相机的重要部件,使用大电流激励长磁透镜可在漂移区产生强磁场,从而提高相机空间分辨率.由于焦耳热效应的影响,长磁透镜无法长时间工作在大电流环境下.本研究基于串并联Marx结构,设计了应用于长磁透镜的电流脉冲发生器,研究了充电电压、储能电容、负载以及电路串、并联级数对输出电流脉冲的影响.当充电电压增大,储能电容值增大,负载减小,串联级数增加时,脉冲峰值电流增大;并联级数增加时,峰值电流呈先增后减的变化趋势.当储能电容值增大,负载增大,串联级数减少,并联级数增加时,脉冲半高宽增大.建立长磁透镜模型,模拟了长磁透镜轴上磁场强度分布.长磁透镜内径越大,轴上磁感应强度越弱;激励电流越大,磁感应强度越强.采用四级串联、两路并联的Marx脉冲电路产生了峰值457 A,半高宽6.76 ms的电流脉冲.该电流脉冲激励长磁透镜,获得了53.72μm的空间分辨率.

基于Camera Link接口的高帧频数字图像采集显示系统

设计了基于FPGA的嵌入式图像采集显示系统,并对该系统采用的接口协议、匹配端口和软硬件架构进行了研究.给出了系统各个功能模块的设计方法,对系统中接口模块的信号时序和图像数据缓存处理架构进行了软件编写及仿真.实验结果表明:满足了降低成本、节约空间、提高系统稳定性和工作带宽的要求.

矿用激光雷达与相机的无目标自动标定方法研究

矿用车辆实现无人驾驶依赖于准确的环境感知,激光雷达和相机的结合可以提供更丰富和准确的环境感知信息。为确保激光雷达和相机的有效融合,需进行外参标定。目前矿用本安型车载激光雷达多为16线激光雷达,产生的点云较为稀疏。针对该问题,提出一种矿用激光雷达与相机的无目标自动标定方法。利用多帧点云融合的方法获得融合帧点云,以增加点云密度,丰富点云信息;通过全景分割的方法提取场景中的车辆和交通标志物作为有效目标,通过构建2D-3D有效目标质心对应关系,完成粗校准;在精校准过程中,将有效目标点云通过粗校准的外参投影在逆距离变换后的分割掩码上,构建有效目标全景信息匹配度目标函数,通过粒子群算法最大化目标函数得到最优的外参。从定量、定性和消融实验3个方面验证了方法的有效性:(1)定量实验中,平移误差为0.055 m,旋转误差为0.394°,与基于语义分割技术的方法相比,平移误差降低了43.88%,旋转误差降低了48.63%。(2)定性结果显示,在车库和矿区场景中的投影效果与外参真值高度吻合,证明了该方法的稳定性。(3)消融实验表明,多帧点云融合和目标函数权重系数显著提高了标定精度。与单帧点云相比,使用融合帧点云作为输入时,平移误差降低了50.89%,旋转误差降低了53.76%;考虑权重系数后,平移误差降低了36.05%,旋转误差降低了37.87%。

Night Vision Characteristics and Application of MTV 2821CB CCD Camera

Aim To describe accumulating frames characteristics of CCD camera as a night vision detector. Methods Utilizing CCD external trigger, computer video capture card and image processing software, the image accumulation was made. Results The detection of the static object image whose illuminance on the CCD FPA(focal plane array) was less than 3 7×10 -5 lx was realized and the image's resolution of 300?TV lines was achieved. Conclusion This experimental system can provide a kind of night vision device capable of detecting the static object at low light level and with low cost compared to an image intensifier.

基于视频智能分析的水电厂人员不安全行为自动化检测系统

为保证水电厂的生产生活安全,该文提出基于视频智能分析的水电厂人员不安全行为自动化检测系统。摄像机模块采集区域内视频并发送给资源模块;资源模块存储以及传输数据;自动检测模块获取由资源模块传输的视频两帧间的人员行为前景图像,将其输入至深度置信网络中,输出人员行为安全性判断结果,并返回至资源模块;若检测模块检测到不安全行为,资源模块会将不安全信号传递给报警模块发出报警。通过实验可知,该方法获取的视频采集结果细节全面、清晰,提取的人员行为前景图像的交并比高,可实现人员不安全行为准确检测。

同步触发和级联滤波的分幅相机皮秒高压脉冲研究

脉冲展宽分幅相机是脉冲展宽技术与微通道板(microchannel plate,MCP)分幅相机的结合体,其时间分辨率与皮秒高压脉冲呈非线性波动关系.采用同步触发模式和级联结构LC高通滤波器产生皮秒高压脉冲,将其与影响时间分辨率的阴极电压和漂移距离结合,应用于脉冲展宽分幅相机的时间分辨率研究中.结果表明,同步触发式多级Marx电路能产生半高宽优于1 ns的高压脉冲,随着级联LC高通滤波器从1阶增至7阶,产生皮秒高压脉冲的半高宽从558 ps降至409 ps,幅值从-3.6 kV降至-1.4 kV,上升沿斜率的非线性波动为5.03~10.25 V/ps;将其加载于MCP通道内的光电子倍增模型,获得的MCP分幅相机时间分辨率由206 ps提高至149 ps;而将其应用于脉冲展宽分幅相机,随着阴极电压和漂移距离增加,时间分辨率的非线性波动为3.8~39.4 ps.通过数据统计和对比发现,当同步触发Marx电路与3阶LC高通滤波电路相结合时,脉冲展宽分幅相机的时间分辨率能达到最优.

静电聚焦提升脉冲展宽分幅相机空间均匀性

为提升脉冲展宽分幅相机的空间分辨均匀性,利用静电聚焦等位面均匀和像面漂移小的特性,采用静电透镜设计成像系统,构建脉冲展宽分幅相机电场分布和成像特性的关系,利用空间调制传递函数评估空间分辨率,并通过将空间分辨率的数值波动转换为梯度变化百分比的形式,对区域内的空间分辨率不均匀度进行定量描述.研究结果表明,等径双静电透镜成像系统能够增大探测区域,并降低空间分辨率不均匀度,满足脉冲展宽分幅相机向大面积探测的发展需求.在漂移区长度为400 mm,透镜孔径、轴向宽度和间距分别为200 mm、60 mm和210 mm的情况下,为避免电极电压过高引起的等位面均匀性变差和电子能量弥散增加,当第1和第2透镜电极分别加载-4.5 kV和10.0 kV电压时,脉冲展宽分幅相机的有效探测区域半径可达21 mm,离轴空间分辨率的波动范围为321.4~340.3μm,探测区域内的空间分辨率不均匀度为(1.11×10^(-4))%,均优于3磁透镜成像系统40.08~482.29μm的波动范围和0.027%的不均匀度.研究结论可为静电聚焦成像系统在脉冲展宽分幅相机中的应用提供理论基础,有助于量化并提升空间分辨率的均匀性.

基于Camera Link的高速图像采集技术研究与应用

针对光学测量图像采集存储系统存在的系统可靠性低、丢帧率较高的问题,研究了基于Camera Link的高速图像采集技术,提出了帧频驱动采集与实时检测采集融合的控制方法以及改进型双缓存数据采集方法,并将该技术应用在光学高速电视测量系统,提高了系统可靠性,消除了图像丢帧、错图;该技术通用性强,可以广泛应用在基于Camera Link的图像采集存储系统,具有较大的应用推广价值。

Design of a control system with high stability for a streak camera using isolated ADC

The streak camera is an ultra-fast diagnostic instrument with high sensitivity, and a high temporal and spatial resolution. It is primarily employed in various scientific research, such as inertial confinement fusion(ICF),synchrotron light sources, and electron–positron colliders.An automatic control system for an X-ray streak camera is presented in this paper. The output terminal of an analogto-digital converter was isolated from its input terminal, to reduce interference from high-voltage electrodes. Compared with traditional methods, this scheme also improved the internal electromagnetic interface immunity. Therefore,the system stability was enhanced. With this optimized control system, some characterizations of the streak camera were measured. Static and dynamic spatial resolutions of 25 and 20 lp/mm(CTF = 20%), respectively, were obtained. In addition, a dynamic range of 552:1 and a temporal resolution of 7.3 ps were achieved. The results confirmed that these characterizations are sufficient for the specifications derived from the diagnostic requirements of ICF.

A rapid and convenient experimental method of absolutely calibrating transmission of x-ray flat-response filter

We develop a rapid and convenient experimental method of absolutely calibrating the transmission of an x-ray flatresponse filter. The calibration experiment is performed on a small laser-target facility, and a set of high resolution holographic flat-field grating spectrometers is used as a discrimination system of the laser-produced x-ray source. Given that the holographic flat-field grating has a relatively large width, the grating is divided into two regions for use in that direction,where one region has the filter added and the other region does not. The filter transmission is determined by dividing the x-ray signal counts detected when the filter is in the line of sight by those detected when the filter is out of the line of sight.We find that the calibration results of this experiment agree with the calibration results using a synchrotron radiation source,as well as simulation results. Our method is not only highly reliable but also rapid and convenient.

Use of Accelerators for Biomechanical Analysis of Walking Motion Aided by Wheeled Walking Frames

Walkers improve self-reliability. We examined the effectiveness of a newly developed wheeled walking frame for use by physically handicapped persons. Unstable gaits in walker users were analyzed by tri-axial accelerometers and a motion capture system. Several markers were placed on subjects＇ backs and legs. Subjects were requested to walk around a test course at a comfortable speed, while their motion was recorded by two high-speed video cameras. The activities performed on the test course comprised standing, normal walking, fast walking, and walking over a barrier. Any accidental falls were also recorded. We established the characteristic rules of gait motion using a walker. Furthermore, we demonstrated that gait characteristics are more conveniently extracted from acceleration sensors than from motion capture systems, since the sensors can be affixed to subjects for self-monitoring and goal achievements. The methods employing acceleration sensors are considered suitable for determining the average gait motions of elderly persons living in nursing homes, and can be used to evaluate walking motion before and aider rehabilitation.

用于高速碰撞过程拍摄的5万帧摄像系统设计

为了近距离清晰拍摄某高速运动目标的碰撞过程,研究了一种高帧频摄像系统。由于摄像系统的前端可能遭受碰撞碎片的损坏,研究了一种保护窗组件。针对成像单元的FPGA在极端高温+70℃时温度过高的问题,研究了一种导热装置。采用七组成像单元在顺序脉冲的控制下接续拍摄的方法,实现了5万帧/秒的高帧频成像。保护窗组件采用了三组保护窗玻璃自动移动更换且可自锁的形式,采用蜗轮蜗杆传动机构实现了大传动比驱动和自锁功能,采用霍尔传感器对保护窗的位置进行实时反馈。导热装置中间部分采用了柔性的高热导率石墨板,既有效地将FPGA的热量传导至主壳体上,又解决了装调节环节中刚性导热装置的过定位问题。对装配好的高帧频摄像系统进行了相关的力、热实验。实验结果表明,保护窗组件自锁和移动切换功能正常,高帧频摄像工作正常,实测拍摄帧频为50 050帧/秒,满足近距离清晰拍摄某高速运动目标碰撞过程的要求,具备一定的防护能力和热环境适应能力。

基于深度相机的古建筑木结构裂缝识别联合多分辨率三维重建方法

目的研究木结构古建筑的三维数字化技术以及木结构表面裂缝分析方法,为该类古建筑的裂缝测量和维护提供参考。方法通过Mask R-CNN对RGBD图像中的裂缝信息进行识别,结合位姿优化策略计算每一帧的相机姿态,进而获得裂缝的三维信息;构造一种包含古建筑三维模型与裂缝信息的多分辨率三维重建模型,基于所构造的模型分析古建筑表面裂缝的长度和深度。结果提高裂缝三维重建精度前,长度平均计算误差为12.3%,深度平均计算误差为36.8%;提高裂缝三维重建精度后,长度平均计算误差为9.3%,深度平均计算误差为19.7%。结论提出的识别方法可以快速、精准地识别古建筑木结构中的裂缝并获得古建筑的三维模型,相较于传统裂缝测量效率更高、成本更低。

基于USB摄像头的单摆频闪照相实验系统的设计与开发

传统的频闪照相实验通常在暗室中进行,对操作环境有一定要求。本文设计开发了一种基于USB摄像头的单摆频闪实验系统,可以在明亮的教室中使用,便捷高效。用USB摄像头实时拍摄摆球的运动情况,利用帧间差分法确定摆球的相对位置并一键生成频闪照片,显示摆球运动轨迹,摆球的运动周期通过傅里叶变换计算得到。实验结果表明,该系统具有较高的测量精度,配合投影仪使用,演示效果直观明显,可以很好满足实验教学要求。

基于脉冲功率合成技术的宽微带分幅成像驱动技术研究

针对行波选通分幅相机超宽画幅驱动需求,基于宽带多节威尔金森脉冲功率合成方法,设计了一款高压驱动脉冲源。基于有限元分析方法,采用仿真软件对脉冲功率合成电路进行了仿真,系统分析了端口驻波比、插入损耗、端口隔离度、幅相一致性等参数。根据仿真分析完成了脉冲功率合成电路研制,验证系统最终能够利用8路峰值电压为1.3 kV左右、脉冲宽度为3.5 ns左右、脉冲前沿在600 ps左右的单路脉冲合成峰值电压超过3.2 kV的高压脉冲,脉冲宽度在3 ns以内,脉冲前沿在600 ps以内。脉冲频谱范围在300 MHz到3 GHz范围内的两路合成效率为83.5%,特定频率下为88%,八路脉冲合成效率为58%,特定频率下可以达到68%。通过该电路合成的高压脉冲可用于驱动宽20 mm、长95 mm、等效阻抗6Ω左右的微通道板实现选通成像,验证了基于宽带多节威尔金森电路实现脉冲功率合成,提高分幅相机驱动脉冲功率的可行性。目前基于该技术的高压驱动脉冲源已应用于I-MCP1.0型分幅相机。