A method of evaluating the near diffracted field

A simple expression for the diffracted field by a slit or a flanged parallel-plate waveguide is derived from which we can readily evaluate the near field by applying the fast Fourier transform. Some numerical results are presented for the diffracted wave of an isotropic cylindrical wave by an infinitely long slit in a thin conducting screen.     

X射线衍射形貌术在碲锌镉晶体中的应用

碲锌镉晶体中存在着各种典型晶体缺陷,X射线衍射形貌术是一种非破坏性地整体研究晶体材料结构完整性、均匀性的有效方法。本文将反射式X射线衍射形貌术应用于碲锌镉晶体质量的评价,研究了入射线狭缝宽度、积分时间、扫描步长等测试参数以及样品表面加工状态对X射线衍射形貌的影响。结果表明入射线狭缝宽度对碲锌镉晶体的X射线衍射成像及晶体质量筛选应用影响很大,积分时间、样品扫描步长等测试参数的选择与入射线狭缝宽度密切相关。     

狭缝投影位置传感技术及其在精密定位中的应用

提出了一种基于狭缝投影的位置传感技术，阐述了此技术的传感原理及其在精密定位中的应用。准直激光束照明的投影狭缝由一个透镜以掠入射角度投影在被测物体上，狭缝投影经过被测物体表面的反射和另一个透镜的成像在探测双缝上形成投影狭缝像。探测双缝放大成像在双像限探测器上，投影狭缝像透过探测双缝的光强分别被双像限探测器的两个像限所接收，通过检测双像限探测器两个像限上的光强获得被测物体的位置。实验验证了此传感技术的可行性，其位置重复测量偏差小于32nm（1σ）。     

径向偏振光纯度检测及偏振态分布特性评价

光束横截面内偏振态分布均匀性是影响径向偏振光光束质量及其实际应用的关键因素。通过PBS测量法、狭缝法和S波片法三种方法对径向偏振光偏振纯度进行测量和对比,分析了径向偏振光偏振态在横截面内分布均匀性。在PBS测量法和狭缝法测量径向偏振光过程中,给出了径向偏振光纯度表达式,分别测得径向偏振光纯度为93.4%和84.1%,并引入方差公式评价径向偏振光偏振态分布均匀特性。其中PBS测量法表达径向偏振光纯度更为准确,狭缝法可以通过比较不同区域偏振度更精确地反映径向偏振光偏振态分布特性。S波片法可以使用市场现有偏振分析仪间接测量径向偏振光纯度,更适应于测量径向偏振光在放大过程中偏振态变化情况。     

预置狭缝法彩虹全息图视角的理论分析

对用预置狭缝法和带平面反射镜的预置狭缝法制作的彩虹全息图的视角问题作了详细的讨论。提出了既可以保证能量利用率,又可以进一步扩大再现视角的简单方法——斜放平面反射镜的预置狭缝法。对平面镜的最佳位置及所能具有的最大视角进行了分析和讨论,给出了相应的计算公式。讨论了上述几种方法的使用条件及所受限制,并比较了在某些情况下各自的最大视角。另外定义了有效再现狭缝的概念,以区别于通常的再现狭缝     

成像狭缝对热红外高光谱成像仪接收能量的影响

由于热红外高光谱成像仪的狭缝宽度与成像波长在同一量级,光在其内部传播时能量发生损失而不能全部被探测器像元接收,因此基于几何光学的计算像元能量的方法已不再适用。为了探究能量损失情况,采用时域有限差分方法计算了热红外高光谱成像仪中光聚焦入射狭缝前表面时狭缝后光强的分布,并利用瑞利-索末菲矢量衍射理论得到了远场光强分布,从而分析了不同狭缝宽度、狭缝厚度时能量的损失情况,并搭建了实验装置进行验证。结果表明,随着狭缝宽度增加,能量损失逐步减小,且能量主要是由于狭缝后方光波衍射导致能量不能全部进入后级成像镜头而损失,在狭缝内部损失的能量很少。当狭缝宽度为几十微米量级时,狭缝厚度对能量损失影响不大。     

不规则深缝宽度的检测

提出了一种检测不规则深缝宽度的方法，成功地检测了发动机活塞环外缘与缸体内壁的间隙，检测的最小缝宽为2μm。     

用凸透镜测狭缝宽度

提出利用凸透镜成像原理测出狭缝宽度的一种新方法,实验采用两种光源对一狭缝凸透镜成放大像。利用像宽结合公式计算出实现狭缝的宽度,该方法与现行其它测量方法相比较,具有操作简便,测量狭缝宽度范围广,1mm以上的宽度都可以测量,准确度高,所用仪器简单等特点。     

On the equivalent circuit representation of the slittedparallel-plate waveguide filled with a dielectric

An investigation of the equivalent π circuit representation for the transverse slit in the wall of a transverse electromagnetic (TEM) parallel-plate waveguide is presented. For the narrow slit, approximate analytic expressions for the equivalent circuit parameters are given in terms of the centerline representation and, for the arbitrarily width slit, the equivalent circuit parameters are considered by the method of moments in terms of both the centerline representation and edge representation, and various characteristics of the equivalent π admittance circuit representation are discussed. A critical look is taken at the validity of the previous model of th E-plane gap coupling between two rectangular microstrip patch antennas, and the improved model is considered for the narrow slit (gap) width case     

激光参量对血管支架切缝形貌及粗糙度的影响

为了研究激光加工工艺参量对血管支架切缝形貌以及表面粗糙度的影响，采用不同参量对比分析试验法，开展了心血管支架316L材料光纤激光切割实验，分析了激光脉冲宽度、激光功率和切割速率等不同工艺参量对材料切缝形貌及粗糙度的影响，得出激光切割支架的最佳工艺参量组合。结果表明，不同区域切缝形貌和表面粗糙度存在差异性，其中支架切缝的汽化区厚度主要受脉冲宽度及激光功率影响，当脉冲宽度为35μs时，支架切缝汽化区厚度最大可达到120μm；支架切缝汽化区粗糙度随切割速率增加先减小后增大，当切割速率为6mm/s时，切缝表面粗糙度值最低为650nm。此研究结果为心血管支架光纤加工的研究及后续光整加工奠定了理论基础。     

激光切割锂电池负极极片复合材料的数值模拟

为了探究负极极片复合材料的切割性质, 采用有限元模型, 对激光切割锂离子电池负极极片复合材料温度场进行数值模拟计算。由温度场分布取得了负极切缝宽度与切缝深度的尺寸大小, 从中研究激光功率、切割速率和光斑半径对负极表层材料切缝宽度与切缝深度的影响。结果表明, 负极表层切缝宽度随激光功率和光斑半径的增加而增大, 随切割速率增大而减小; 切缝深度随激光功率增加而增大, 随切割速率和光斑半径增大而减小。切割至中间铜箔后, 切缝深度变化速率趋缓, 负极材料的复合结构对切缝深度存在明显影响; 在功率为170W、光斑半径为47μm、切割速率变化至600mm/s左右时, 效果最为明显, 切割深度在该参量下达到60μm, 且突破这一阈值后增长速率得到明显提升直至极片完全切断。这一结果可为激光应用于锂离子电池极片复合材料切割提供参考。     

激光扫描共聚焦光谱成像中的出射狭缝控制

激光扫描共聚焦光谱成像系统需要在光谱带位置处设置一个出射狭缝,通过改变狭缝的宽度和狭缝相对于光谱带的位置,实现对于特定谱段荧光的选择。出射狭缝由两个安装在步进电机上的可移动缝片形成,通过伺服控制的方式,利用ARM芯片生成步进电机的控制信号,并根据编码器和光耦开关提供的位置负反馈进行调整,以实现对于三路通道中狭缝位置与宽度的精确设置。通过实验证明,本文所设计的出射狭缝控制系统能够对缝片位置进行精确设置,实现了同时对样品中不同波段荧光成分进行成像的功能,提高了对于荧光样品观测的灵活性与观察效果。     

Remote detection of a thin slit in a thick ground plane

A method for detecting a thin slit in a thick ground plane is discussed. The method is based upon detecting the slit resonances which occur when the thickness of the ground plane is approximately an integer order of half-wavelengths. A theoretical model for the scattering from a two-dimensional slit by a short current element is also described. Both theory and experiment display the slit resonances.     

Gas dynamic CO2-He-(N2) laser investigations

Experiments on IR laser action and gain measurements are reported for a CO2-containing gas mixture flow that cools as a result of expansion. The mixture is preheated by a reflected shock wave, and the gas is expanded into a vacuum through a slit. Laser action is obtained in a CO2-He mixture, while the addition of nitrogen increases the gain. The gain was found to depend on the distance from the slit and the gas pressure before the slit.     

Characteristics of a parallel-plate waveguide with a narrow slit in its upper plate

A parallel-plate waveguide with a narrow slit in its upper plate is investigated. The magnetic current induced in the slit is obtained from an integral equation whose kernel is approximated to a logarithmic function. From knowledge of the magnetic current, the normalised conductance and susceptance of the slit are computed.     

Electron beam lithography and ion implantation techniques for fabrication of high-Tc Josephson junctions

Established semiconductor process technologies are demonstrated to be suitable for the fabrication of high temperature superconductor (HTS) Josephson junctions. Single YBCO bridges were modified by local oxygen ion irradiation through a narrow slit in a PMMA mask which was formed by electron beam lithography. The influence of slit dimension and irradiation dose was investigated. The critical current and normal resistance ot the modified microbridges can be controlled by these two parameters. Proximity coupling across the modified region is observed up to a slit width of 250 nm. When exposed to microwave irradiation the microbridges exhibited Shapiro steps. In dc SQUIDs a voltage modulation as a function of an applied magnetic flux is observed.     

Diffraction characteristics of a slit in a thick conducting screen

The diffraction of a plane electromagnetic wave by a slit in a conducting screen of finite thickness is investigated using the Wiener-Hopf and generalized matrix techniques. For purposes of the analysis, the diffraction by two identical semi-infinite parallel-plate waveguides forming a tandem slit configuration is treated first in order to determine the interaction between the open ends of the waveguides. This interaction term is then utilized in solving for the thick slit geometry which is obtained by filling the parallel-plate regions with a dielectric whose relative permittivity is allowed to approach infinity. Although the integral equations occurring in the tandem slit configuration are similar to those given by Jones for the parallel-strip case, they are solved here by a somewhat different method. In contrast to the limitation on the strip-strip separation imposed by Jones, our solution is not restricted to the special case of large separation between the two slits. For anE-polarized incident plane wave, the far field diffracted by each edge of the thick slit is viewed in ray-optical terms as that due to a thin edge centered at the middle of the thick edge modified by a multiplication factor. The thick edge-edge interaction term, on the other hand, is also modified such that each thick edge is viewed by the other as a combination of a line source as well as a line dipole which vanishes when the thickness approaches zero. It is shown that for ratios of screen thickness to slit width belowapprox0.5, the beamwidth is larger than that of the thin slit, while for larger ratios the beamwidth is smaller. Typical diffraction patterns, which are in good agreement with experiment, are presented to illustrate this phenomenon.     

九谱段焦面配准测试仪的研制

多通道焦面遥感相机通道间的配准是相机总装定焦过程中的关键技术,通道间的配准精度决定了后续通道融合后的遥感图像质量。设计并完成了一套用于解决九谱段双通道焦面配准的测试仪。积分球照明一条狭缝,经平行光管成像在无穷远,照明九谱段相机,在相机焦面上得到一个竖直放大的狭缝像。四谱段、五谱段线阵探测器分别位于双通道焦平面上,分别调整双通道焦面的位置,计算四谱段、五谱段探测器上狭缝像的质心位置,通过质心位置来评价通道间像元的对准精度。该仪器解决了多通道焦面遥感相机通道间的配准问题,配准精度达亚像元量级,保证了通道融合后的图像质量。     

激光测量中狭缝非均速移动引起的失真及校正

在红外大功率激光功率密度分布的测试研究中,利用平动狭缝采样,通过计算机对采样光斑的灰度处理获得激光功率密度,是一种方便适用的方法.讨论了狭缝非均速运动对采样结果的失真及其校正方法.     

金属周期性结构光栅亚波长凹槽对透射率的影响

利用时域有限差分算法(FDTD)模拟了二维金属光栅的电磁场,分析了金属光栅透射率随波长的变化.金属的介电常数随频率变化关系采用Drude模型.金属光栅每个单元刻蚀有1个亚波长宽度的缝和1个相同宽度的凹槽,凹槽深度可变.这种结构相对于1个周期内只有1个狭缝的结构,透射率曲线上出现1个凹陷,加深凹槽的深度,这个凹陷的位置会向长波方向移动.给出了一个简单的解析式来近似确定透射率中出现凹陷的位置.