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温度对太赫兹亚波长金属结构共振特性的影响
太赫兹 温度 亚波长金属结构
2016/8/11
利用太赫兹时域光谱系统研究温度对GaAs基底上生长的太赫兹亚波长金属结构的透过率及共振特性的影响。实验发现,温度从低温80 K升高至380 K,样品的透过率逐渐降低,且低频共振频率处有轻微的红移现象。通过研究共振带区域及远离共振带区域的透过率情况,分析了总体透过率降低的根本原因在于温度升高导致GaAs基底的本征载流子浓度升高;共振凹陷减弱是由于基底载流子的变化致使透过率升高形成的;红移现象的产生是...
基于半导体行业中PCB焊膏印刷检测的实际应用, 采用0.45 WXGA DMD芯片设计了数字条纹投影光学系统.以LED作为光源, 结合透镜阵列照明DMD芯片;同时, 为了减小投影三角关系造成的条纹周期不均匀性对检测结果的影响, 采用双远心光路结构将DMD生成的条纹成像到待测表面, 且适用的最小检测面积为1mm2.光学模拟结果表明, 该数字投影系统在被投影表面上的照明均匀性为91%, 投射条纹的对比...
提出了一种基于基元全息图频谱分析的计算全息参考光角度选择方法.通过分析基元全息图的空间频谱成分, 导出全息图正确再现需要满足的约束条件;求解了基于空间光调制器的计算全息再现系统的参考光角度取值范围;用N-LUT算法计算了成像距离为1 000 mm时, 一幅22.5 mm×26.1 mm的二维图像取不同参考光角度时的全息图, 并进行了数字再现和光学再现实验.结果表明:参考光角度在0.893 8°到1...
飞秒径向偏振光紧聚焦实验
径向偏振光 紧聚焦 实验研究 高数值孔径
2016/11/30
以飞秒激光器为光源,搭建记录测量聚焦光斑的光学实验系统,研究飞秒径向偏振光紧聚焦特性.数值模拟表明当物镜数值孔径为0.9,波长为750 nm时,线偏振光和径向偏振光焦斑的最小半高全宽分别是1.3 μm和1.0 μm.实验中,使用全息干板作为记录介质,记录和测量微小的聚焦光斑,并通过精密电动平移台实现几十纳米量级步长的移动,获得精确焦平面处的聚焦光斑.测量结果表明,线偏振光和径向偏振光焦斑的最小半高...
针对基于时间平均数字全息法的微振动原位检测,提出了一种有效提高振动条纹模式对比度的方法,进而可准确获得待测面振幅分布.首先针对实际振动过程中物体存在纵向微位移而引起的相位误差进行校正;然后去除记录过程中物光场散斑引起的相位噪音,有效提高了被第一类零阶贝塞尔函数调制的条纹对比度;最后利用第一类零阶贝塞尔函数的变化规律和条纹级数,定量估计全场的振幅分布.搭建了以声波作为激励源的时间平均全息测振实验系统...
针对数字全息图像背景去除的问题,提出两种全息图像重建去背景的方法:背景减弱法和自适应滤波法.搭建了共轴数字全息显微成像实验系统,利用该系统分别对洋葱表皮、植物根茎横切标本、叶片气孔标本和血细胞标本进行背景去除和图像重建.通过光强分布曲线、对比度计算等证明了自适应滤波方法在共轴数字全息结构中去除背景的有效性.实验结果表明,根据环境、样品等不同,全息图的背景也会发生变化.基于此结果,将全息数字显微图像...
环境对大口径SiC轻量化主镜视宁度的影响
大口径望远镜 SiC轻量化主镜 视宁度 温度梯度
2015/12/23
由于地基大口径望远镜主镜视宁度与望远镜系统成像质量相关,本文研究了环境对主镜视宁度的影响。理论分析了影响主镜视宁度大小的因素,得出主镜视宁度会随主镜表面和环境之间温差的增大而增大的结论。利用有限元法分析了自然对流和吹风条件下主镜的温度变化和温度分布;最后通过相应工况条件下2 m SiC轻量化主镜的温度测试实验对仿真分析结果进行了验证。实验结果显示:在初始温差为6℃的无风自然对流情况下,主镜与环境达...
Automated Extraction of 3D Trees from Mobile LiDAR Point Clouds
Mobile LiDAR Tree Extraction Shape Context Segmentation Point Cloud
2014/7/30
This paper presents an automated algorithm for extracting 3D trees directly from 3D mobile light detection and ranging (LiDAR) data. To reduce both computational and spatial complexities, ground point...
Evaluations of Three-Dimensional Building Model Reconstruction from LiDAR Point Clouds and Single-View Perspective Imagery
3D Building Model Reconstruction LiDAR Single View Reconstruction Image-based Reconstruction Close-range Photogrammetry
2014/7/30
This paper briefly presents two approaches for effective three-dimensional (3D) building model reconstruction from terrestrial laser scanning (TLS) data and single perspective view imagery and assesse...
Indoor Modelling Benchmark for 3D Geometry Extraction
Indoor 3D Modelling Benchmark Terrestrial Laser Scanning Segmentation Reconstruction
2014/7/30
A combination of faster, cheaper and more accurate hardware, more sophisticated software, and greater industry acceptance have all laid the foundations for an increased desire for accurate 3D parametr...
A comparison of multi-view 3D reconstruction of a rock wall using several cameras and a laser scanner
Close Range Photogrammetry Camera Comparison Accuracy Three-dimensional Modelling Engineering Application Geology
2014/7/30
This work presents a comparative study between multi-view 3D reconstruction using various digital cameras and a terrestrial laser scanner (TLS). Five different digital cameras were used in order to es...
Image based 3D city modeling : Comparative study
Virtual 3D city model Sketch based 3D model Procedural grammar based 3D model Close Range Photogrammetry based 3D model Computer Vision based 3D model
2014/7/30
3D city model is a digital representation of the Earth’s surface and it’s related objects such as building, tree, vegetation, and some manmade feature belonging to urban area. The demand of 3D city mo...
Processing lidar waveform data for 3D visual assessment of forest environments
Forestry Full Waveform Lidar 3D modelling Visual representation
2014/7/30
The objective of this report is to present and discuss a work-flow for extracting, from full-waveform (FW) lidar data, formats which are compatible with common information systems (GIS) and statistica...
Close-range imaging and research priorities in Europe
Close-range imaging metrology cultural heritage research Horizon 2020 EU
2014/7/30
Since 1984, the European Union’s Framework Program for Research and Innovation has been the main instrument for funding research. Specific priorities, objectives and types of funded activities vary be...
Kinect Fusion improvement using depth camera calibration
Calibration Depth Map Kinect 3D modelling Fusion Libraries
2014/7/30
Scene's 3D modelling, gesture recognition and motion tracking are fields in rapid and continuous development which have caused growing demand on interactivity in video-game and e-entertainment market....