基于空间光调制器的光束大角度扫描技术研究

为实现一束激光在90°锥形范围内的扫描,利用液晶空间光调制器在光束偏转控制时精度高、无机械惯性等优点,研究并建立了基于液晶空间光调制器的光束偏转和角放大光路系统。提出了空间光调制器的可编程相位调制算法和角放大光路结构,推导了空间光调制器光束偏转角度与相位灰度驱动图的关系,设计了角度放大倍率高于22倍的角放大光路系统。在此基础上,建立了光束扫描控制实验系统,对该装置角度出射范围进行了测量,将实际的角放大倍率与设计值进行对比。实验结果表明:研制系统的出射视场角可达91.22°,并可通过畸变校正实现出射视场角范围内的规则形状扫描。该研究在光束敏捷控制、无线激光通信、目标搜索与追踪等领域具有重要的研究价值和应用前景。     

The influence of substrate geometry on the emission properties of a liquid metal ion source

The effect of needle radius, cone angle and shaft diameter on the threshold voltage and angular intensity — total current relationships for a Ga liquid-metal ion source (LMIS) was investigated. The variation of threshold voltage with needle geometry could be described in terms of the Taylor theory of liquid cone formation by electrostatic fields. The beam energy spread was mainly a function of total source current and was not a sensitive function of emitter geometry. Source angular intensity at a constant total current increased linearly with threshold voltage when the latter was altered due to source geometry.     

基于温敏漆技术的圆锥高超声速大攻角绕流背风面流动结构实验研究

高超声速流动中, 大攻角下圆锥背风面边界层会存在流动分离与再附、边界层转捩等多种流动现象, 进而对圆锥表面温度分布产生显著的影响。为了对这一复杂流动规律及其对表面温升分布的影响进行讨论, 研究基于温敏漆技术, 得到了在Mach数为6的低湍流度来流条件下, 攻角为10°的圆锥背风面温升分布结果。通过对不同位置、不同方位角处温升分布曲线的分析, 对大攻角下圆锥背风面边界层流动发展过程及不同发展阶段的流动特征进行了讨论。同时, 通过对来流总压的调节, 得到了不同Reynolds数下的圆锥背风面温升分布结果, 总结了Reynolds数对流动的影响规律。研究发现, 高超声速大攻角圆锥背风面边界层流动发展过程中会依次出现层流分离、定常横流涡影响、转捩以及湍流分离与再附等流动特征, 而在不同的Reynolds数下, 各个流动特征产生影响的范围不同, 随着Reynolds数的降低, 层流范围和定常横流涡影响范围均有所增加, 而从观察到横流影响到转捩开始发生的范围基本相同。      

空心锥状双高斯光束传输特性研究

建立了空心锥状双高斯光束的模型.在空心高斯光束模型的基础上,由初始光场的光强分布,利用柱坐标下的柯林斯公式,导出了空心锥状双高斯光束经过傍轴光学系统的解析传输变换式由传输变换式计算分析了空心锥状双高斯光束在自由空问的可控传输特性,及在1,10和60 m的截面光环的光强分布.用KNbO3双轴晶体进行实验,获得了空心锥状双高斯光束,外锥折射的锥角等于入射光会聚角.实验表明,当空心光束处于锥状发射状态时,空心光束的光环内黑斑面积随传输距离的增加而增加,实验结果与模型吻合较好.该研究为进一步设计制备基于空心锥状舣高斯光束的新型激光元件提供了理论依据和设计参量.     

激光动态外锥折射实验研究

根据双轴晶体的锥形折射效应，提出锥角可控的动态外锥折射以及一种实现外锥折射的新方法；选用ＫＮｂＯ３晶体进行实验，不仅观察到外锥折射，而且实现了锥角在０°～８°范围内的外锥折射扫描控制     

基于无衍射光莫尔条纹的轴锥透镜锥角测量方法

为了准确地测量轴锥透镜锥角值,根据无衍射光同心圆环间距不随距离改变的特点和莫尔条纹放大的特性,提出了一种基于无衍射光莫尔条纹的轴锥透镜锥角的测量方法。当无衍射光束经分束器分光合束后形成莫尔条纹,平移其中一束光在图像传感器上的位置,实现莫尔条纹数量的变化,通过记录不同莫尔条纹下的中心距离计算出轴锥透镜锥角。实验以锥角为0.5°的轴锥透镜作为被测对象,与CMM测量结果进行比较,该文提出的方法相对测量误差近似为0.54%,重复性为0.86″,验证了该文方法测量轴锥透镜锥角的可行性。     

生物柴油高压共轨喷雾特性的试验研究

应用高速摄影系统与高压共轨系统,在高压定容器内研究了生物柴油的喷雾特性,并与柴油进行了对比。结果表明,生物柴油油束形态比柴油细且长,喷雾贯穿距离比柴油大,喷雾锥角比柴油小;高的运动黏度与表面张力导致生物柴油雾化性能比柴油差。随着喷油压力的升高,生物柴油喷雾贯穿距离变长,喷雾锥角增大;随着背压的升高,生物柴油喷雾贯穿距离...     

小攻角下三维细长体定常空化形态研究

基于边界元方法, 使空泡表面和细长体表面分别满足Dirichlet 边界条件和Neumann边界条件, 数值迭代获得小攻角下三维细长体的定常空化形态. 采用线性三角形单元, 将控制点布置在网格节点上, 应用局部正交坐标系并采用迭代方法获得空泡表面的速度势, 进而通过边界积分方程确定空泡厚度的分布. 采用拉格朗日插值方法得到空泡末端的厚度, 避免了迭代过程中网格的重新划分. 数值结果与实验值符合良好, 验证了该方法的合理性. 系统研究了空化数、攻角以及锥角对于三维细长体空化形态的影响规律. 数值结果表明: 攻角使得细长体的空化形态呈现不对称性, 出现空泡向背流面“堆积”的现象; 而空化数越小或锥角越大, 空泡形态的不对称性将越严重. 关键词： 边界元方法 三维细长体 局部空化 攻角     

圆锥边界附近激光空泡溃灭行为的研究

为了研究刚性圆锥边界锥角对激光空泡溃灭行为的影响,文章建立了虚拟平面边界模型, 同时采用阴影摄影术、光偏转法以及数值计算的手段对边界附近空泡溃灭过程进行了研究. 结果表明边界的锥角对空泡的形状、溃灭时间以及液体射流形成均有明显影响. 空泡形状偏离球形的程度和溃灭时间均随锥角的增大而增大,且增大锥角度可以促使射流的形成. 空泡溃灭时间的实验值同理论值具有较高的一致性,验证了虚拟平面边界假设及无量纲距离修正的有效性.     

三维可调式锥体上滚演示实验仪

对传统锥体上滚实验演示仪进行拓展和改进,研制了三维可调式锥体上滚演示实验仪,实现了轨道夹角、双轨道平面倾角及双圆锥体(直径与高度)的连续可调.     

Transition radiation detectors with a dihedral angle or a cone as a radiator

The spectral and angular distributions of the transition radiation produced by a charge crossing an interface shaped like a dihedral angle or a cone are considered. The effects of the variation in the dihedral angle and cone angle, the location of the crossing point on the interface, and the direction of the charge motion on the spatial distribution of the radiation are discussed. The radiation characteristics of the particles that are incident on the interface and those leaving it are given. The features of transition-radiation detectors with dihedral-angle or cone radiators and detectors with plane-surface radiators are compared.     

Formation of Bessel beams with continuously variable cone angle

A simple device capable to produce Bessel beams with variable cone angle is proposed. It is shown that the cone angle of the Bessel beam produced by the axicone placed inside the telescope depends on the position of the axicone and can be continuously varied. As a result of theoretical investigations a simple formula giving the cone half-angle on the parameters and position of axicone inside the telescope was derived. The possibility of the Bessel beam generation with the help of a proposed device was confirmed experimentally. Good qualitative and quantitative agreement with the theoretical predictions is obtained.     

Numerical simulations of laser light guiding and focusing using an open hollow cone

An open hollow cone that can optically guide and focus a laser light into a small beam spot is proposed. The shaping and focusing effects are numerically demonstrated by finite-difference time-domain simulations. The results reveal that the cone-focused laser originates from the multi-beam interference and squeeze of two cone side walls acting like oblique targets. Moreover, the influences of oblique incident angle of laser light, cone angle and cone tip size on the focusing properties are discussed and the optimum cone geometry with cone angle of 16° and tip size of 4.5 wavelengths to achieve high energy concentration at the cone tip is also presented. It is shown that with an open hollow cone a laser light can be focused into a tiny highly localized beam spot of 1 µm diameter and keeps propagating forward for a distance of about 8 wavelengths with a tiny spot diameter remaining almost unchanged. The intensity almost increases up to twentyfold in a 1 µm focal spot.     

光学平台微角振动激光探测方法研究

 设计了精密动态测角实验系统，该系统利用扩束镜正向和逆向不同的光学变换性质，将共孔径双向传输的倍增式角敏光学系统与光电精密位置传感器（PSD）相结合，并从理论上分析了高灵敏光学测角的基本原理，给出了被测角与传感器信号的关系。为消除光电噪声对探测分辨率的影响，信号处理引入了相关检测模式。通过压缩系统噪声信号的等效带宽，从频域中滤除干扰信号的频率成分，实现了从噪声中提取高分辨角度信息。     

基于微扰近似的圆锥表面光散射*

由Hueygen原理出发,介绍了粗糙表面的光散射特性.基于微扰近似,在不考虑遮蔽效应和圆锥顶点的散射情况下,分析了圆锥物体的光散射特性,推导了圆锥物体对平面光的散射场解析表达式.计算了圆锥表面在高度起伏均方根不同情况下对1.06μm光波的散射,并且得到了入射角一定的情况下,不同观察方向的散射光强分布曲线.结果表明,在观察方位角不变时,圆锥的散射光强随观察角顶角的增加先增大后减小|在观测方位角一定时,散射光强随高度起伏均方根的增加而减小,且随观察方位角呈对称分布.     

高超声速圆锥边界层转捩实验研究

在高超声速静音风洞内, 通过基于纳米粒子示踪的平面激光散射(nano-tracer-based planar laser scattering, NPLS)技术、高频压力传感器和温敏漆(temperature sensitive paints, TSP)技术开展了0°攻角条件下7°直圆锥高超声速边界层转捩相关实验研究, 得到了圆锥边界层由层流发展至湍流完整过程的NPLS图像, 清晰地展示了第2模态波的"绳状"结构, 尖锥与钝锥边界层的NPLS结果表明尖锥边界层转捩中第2模态波占主导, 而钝锥边界层在转捩前出现波长约为第2模态波波长5倍(甚至更长)、特征频率不高于31 kHz的狭长涡结构; 采用功率谱密度(power spectrum density, PSD)分析、互相关和N值计算对高频脉动压力数据进行分析, 得到了边界层内扰动波的发展规律, 在尖锥和钝锥中均观察到了沿流向第2模态波幅值先增大后减小、特征频率逐渐降低, 低频成分逐渐增加, 表明边界层发展过程中第2模态率先发展达到饱和, 而后逐渐衰减, 而低频模态则逐渐发展; 通过TSP技术得到了不同单位Reynolds数下的圆锥表面温升分布, 结果表明, 随单位Reynolds数增大, 边界层转捩阵面前移.      

Effect of needle cone angle and air flow rate on electrostatic discharge characteristics of a corona-needle ionizer

In this study, the corona-needle ionizer was designed, constructed, and characterized. Experimental characterizations of the electrostatic discharge in terms of current–voltage relationships of the corona ionizer, including the effects of discharge electrode cone angle and air flow rate were presented. It was found that the charging current and ion concentration in the charging zone increased monotonically with corona voltage. Conversely, discharge currents decreased with increasing angle of the needle cone. The negative corona was found to have higher current than the positive corona. At higher air flow rates, the ion current and concentration were found to be relatively high for the same corona voltage. The effect of air flow rate was more pronounced than the corona voltage. It was also shown that the ion penetration through the ionizer decreased with increasing corona voltage, and increased with increasing air flow rate. The highest ion penetration through the ionizer of the 10° needle cone angle was found to be about 93.7 and 7.7% for positive and negative coronas, respectively. The highest ion penetration for the needle cone angle of 20° was found to be 96.6 and 6.1% for positive and negative coronas, respectively.     

Whispering gallery modes in a conical resonator

A conical closed resonator with perfectly conducting walls is considered. The eigenmodes of the resonator are determined in the first order of perturbation theory, in which the cone angle is a small quantity. A semiclassical approximation is constructed for an arbitrary cone angle; it is shown that the spectrum of whispering gallery modes in this approximation differs insignificantly from the eigenmode spectrum of a cylindrical cavity even for a large cone angle.     

同步卫星扫描视锥与轨道的绘制算法

为了模拟同步卫星在外太空的飞行状态,建设先进的同步卫星模拟仿真系统对于卫星的研制与性能分析有着重要的意义;由于卫星是在特定的轨道上飞行,所以对卫星轨道的绘制建模是卫星模拟仿真系统开发中关键的一环;在这篇文章中介绍了同步卫星与地面观察站通信过程中的扫描视锥与同步卫星运行轨道的绘制算法,重点探讨了基于OpenGL基本矢量图元的绘制以及利用世界坐标系和向量的方法对在绘制过程中所需数据的求解过程;分析了根据同步卫星的运行姿态与其所在轨道的位置来确定同步卫星扫描视锥的角度;最后通过一个虚拟世界的3D引擎验证算法的可行性与绘制效果。