光折变晶体两波耦合增益系数强度特性理论研究

对两中心模型光折变晶体两波耦合增益系数Γ,总的有效陷阱密度N_eff和强度特性因子η(I)的强度特性进行了理论研究。结果显示在两中心模型的光折变晶体中,Γ,N_eff和η(I)有着复杂的特性。当S_Dγ_T/S_Tγ_D小时,对于A类和B类两中心晶体,N_eff随强度的增加而增加最终趋于饱和,当S_Dγ_T/S_Tγ_D大时,对于A类晶体N_eff增加到一个最大值后稍有减少,而对于B类晶体,N_eff增加到最大值后然而有较大的减少。不同类型晶体增益系数Γ有着不同的强度特性是由于晶体中有着不同的能级结构。     

软X射线滤光片用超薄聚丙烯膜

随着宇宙软X射线探测技术的发展,超薄聚合物材料越来越多地作为软 X 射线滤光片用,也作为窗口材料,应用于正比计数器等。如,聚对二甲苯(Parylene-N)、聚脂(Mylar)、聚碳酸酯(Kimfoil)、聚乙烯醇缩甲醛(Formvar)、聚丙烯等。但人们一致认为:聚丙烯是其中最好的软X射线窗口材料。     

合成孔径雷达光学处理器的功能和成像质量的检测

合成孔径雷达光学处理器(OSARP)与普通成像系统不同,它处理合成孔径雷达(SAR),数据片.因此,我们不仅要检测OSARP的成像质量还要检测它的功能.本文提供一种检测OSARP的方法.OSARP的功能是通过检测OSARP各组件的调整量来求得的;OSARP的成像质量是用普通检测靶加位移透镜来检测的.我们使用模拟SAR效据片来检验OSARP处理各种雷达相位历程的能力.最后用真实SAR数据片来检验SAR和OSARP的综合成像质量.用这种方法我们实地检测HG-1型OSARP,实测结果表明这种检测方法是可行的.     

红外折射率精密测试方法的研究

本文阐述了应用最小偏向角法及自准直法测定红外波段折射率的基本原理。并较详细地讨论了最小偏向角的定位问题,探索了用逐渐逼近的光电接收方法测定最小偏向角的规律。对两种方法做了比较。实验装置由 GSJ-A 型数字测角仪加红外反射系统构成。叙述了消除杂光方面所做的工作,保证了测试精度的提高。文中列举了对0.935微米,1.014微米、1.129微米、1.3622微米、1.5295微米、1.7012微米波长测得的晶体材料(CaF₂)、红外光学玻璃(N-344)、普通光学玻璃(Lak₂)及铝酸盐红外材料的折射率典型数据,并对测试结果进行了分析和讨论。本方法获得了±2×10^-2的测试精度,与国外相比已达到了同量级的精度。     

微通道板对软X射线响应的实验研究

在X光成像望远镜中微通道板(MCP)作为焦平面上的成像接收器,探测天体的软X射线辐射图像。本文实验研究在软X射线波段MCP的成像性能以及与此有关的其他性能。作者没计了实验装置,测量了在碳K_a(4.47nm)线下微通道板——荧光屏组件的分辨率,与计算结果进行了比较。提出了一种用软X射线光电发射作为初电流测量MCP电流增益的新方法,具有可反复多次测量、重复性良好及测量方便等优点。测量了在两个波长下微通道板的量子效率及随X射线入射角的变化。     

基于区域分割的自适应反锐化掩模算法

针对线性反锐化掩模法的缺点,提出一种基于区域分割的自适应反锐化掩模法,利用像素局部方差将输入图像划分为平滑区、中等对比度区和高对比度区,根据像素(x,y)所属的区域类型,自适应确定其局部灰阶变化率增益系数α(x,y)及期望的输出局部灰阶变化率H_d(x,y),并导出增强系数K(x,y)。对一幅胸片图像进行处理,并与其它几种反锐化掩模法的处理结果进行比较,结果显示该方法获得较好的边缘增强效果,且有较强的噪声抑制能力。     

Al(PO3)3-NaBF4-AlF3氟磷系统玻璃的研究

本工作利用IR、Raman、X-ray, RTEM及DTA技术首次研究了Al(PO₃)₃-N₃BF₄-AIF₃系统玻璃的基本性质与结构特点, 得出了分相机理及分相与晶化之间关系.实验结果指出, 该系统在高磷区基本保持偏磷酸盐结构.随着A1(PO₃)₃含量降低, 结构逐渐由偏磷酸盐向焦磷酸盐变化.该系统的分相属成核生长机理, 粒子长大服从扩散机制.分相导致整体析晶.     

一个用于卫星的低光平慢扫描电视摄象机

简述猫头鹰(Owl)卫星电视摄象机系统和采用二次电子电导管(SEC)的几种独特的设计特点。分析信噪比对扫描速度的依赖关系,对于一个应用低噪声场效应管的放大器,信噪比可以做到最大限度。最佳扫描速度对应于一个8KHz带宽的放大器和一个超过250MΩ阻值的栅极偏置电阻。为了满足最佳扫描速率和低数据遥测带宽的需要,采用一间歇的扫描方法,用这种方法扫描,扫描电子束仅在一部分扫描时间达到靶的非扫描区域。这个扫描方法综合了低噪声电平和在单扫中高效擦除电荷的优点。单曝光扫描有降低电视系统效率的缺点,只要在光敏面上提供一小的偏置照明,就可避免由于扫描电子束的速度分布而引起的低效率。     

精密机械定位误差的曲线拟合

误差补偿技术能有效地提高精密机械的定位精度。本文以典型的感应同步器数显系统为例,通过对误差曲线的实验和函数分析,并用时间序列AR(n)模型拟合相应的误差曲线。实验证明该方法在微机误差补偿中,占用较少存贮空间,并能较好地处理弱周期性和随机性误差分量。故可用于象座标镇床之类数据庞大的三维精度补偿的场合。     

回束光导摄象管的特性与应用

回束光导摄象管(RBV)是近期发展起来的一种具有特殊性能的摄象管.4¹/2吋 RBV 管的突出特性包括高的孔径响应.高的信号增益,宽的动态范围和大容量的靶面.管子的电学设计参数与其他直读型和回束读出型的成象器件比较,指出了 RBV 管是一个本质上性能要高得多的器件.为了提供更高的灵敏度,正在发展一种带纤维光学耦合象增强器的回束管.RBV 管的运用包括图象传感和静电贮存.已证明总的分辨率可达100对线/mm(每图象高10000电视行).当100对线/mm时,RBV 管的性能可赶上或超过高分辨率胶片的性能.特别是在低对比度的情况下.对稳态光学曝光,读出可以连续进行,或者对于快门曝光或电学记录组成的断续输入,读出可以接近实时完成.对不连续输入,信息可以用慢速扫描单帧读出,或者为了在电视监示器上显示,信息可以用快速多帧读出.在多帧读出方式中,可以得到长达约一分钟的连续的高质量显示.读出传递函数(γ)可以通过电子学来控制.全部读出方式皆允许通过光栅控制和可变焦距进行电子放大.RBV 管好的性能和高的灵活性应能广泛地用在侦察系统,光学和电学贮存及扫描变换.数据取回和发送以及信号处理上.     

3-D measurement and evaluation of surface texture produced by scraping process

The scraping process involves traditional manual work and is an important technique for producing flat bearing surfaces with lubricating grooves on a sliding surface. In order to meet the requirements of precision engineering, the scraped surface should have an equally distributed pattern with a required number of high points per unit area while retaining good flatness. In the machine tool manufacturer’s workshop, however, the quality inspection of scraped surfaces still depends on human eyes. In this study, a 2-D evaluation system is first developed using image processing so that the peak points per area of square inch (PPI) and the percentage of points (POP) can be quantified as parameters. A vision-assisted laser focus probe system is then developed to measure the 3-D form of the scraped profiles. The laser probe is made of a DVD pickup head based on the astigmatic principle. Driven by an XY stage, the entire scraped profile can rapidly be scanned. The quality of the scraped surface can thus be interpreted in a more scientific manner. Based on the measured 3-D data, new evaluation methods are proposed for five parameters, namely the PPI, POP, height of points (HOP) or depth of surroundings (DOS), flatness, and oil retention volume. Experiments show that the 3-D system is consistent with the 2-D system. It not only reveals more surface quality parameters but also uncovers more characteristic surface phenomena than the 2-D image system.     

Three-dimensional microscopy data exploration by interactive volume visualization

This paper presents a new volume visualization approach for three-dimensional (3-D) interactive microscopy data exploration. Because of their unique image characteristics, 3-D microscopy data are often not able to be visualized effectively by conventional volume visualization techniques. In our approach, microscopy visualization is carried out in an interactive data exploration environment, based on a combination of interactive volume rendering techniques and image-based transfer function design methods. Interactive volume rendering is achieved by using two-dimensional (2-D) texture mapping in a Shear-Warp volume rendering algorithm. Image processing techniques are employed and integrated into the rendering pipeline for the definition and searching of appropriate transfer functions that best reflect the user's visualization intentions. These techniques have been implemented successfully in a prototype visualization system on low-end and middle-range SGI desktop workstations. Since only 2-D texture mapping is required, the system can also be easily ported to PC platforms.     

Three-dimensional shape reconstruction from images by shape-from-silhouette technique and iterative triangulation

We propose an image-based three-dimensional shape determination system. The shape, and thus the three-dimensional coordinate information of the 3-D object, is determined solely from captured images of the 3-D object from a prescribed set of viewpoints. The approach is based on the shape-from-silhouette (SFS) technique, and the efficacy of the SFS method is tested using a sample data set. The extracted three-dimensional shape is modeled with polygons generated by a new iterative triangulation algorithm, and the polygon model can be exported to commercial software. The proposed system may be used to visualize the 3-D object efficiently, or to quickly generate initial CAD data for reverse engineering purposes, including three dimensional design applications such as 3-D animation and 3-D games.     

Characterizing Subsurface Archaeological Structures with Full Resolution 3D GPR at the Early Dynastic Foundations of Saqqara Necropolis,Egypt

Currently, Ground Penetrating Radar (GPR) used in archaeological prospection is based on 2-D parallel line methodologies characterized by line spacing from 0.25 to 1 m (common line separation is 0.5 m) with different GPR antennas and extensive interpolation used to fill data gaps. High resolution 3-D GPR images of the subsurface can be obtained by recording data with a quarter wavelength grid spacing in all directions. Recently, we used a new GPR system which is a combination of commercial GPR with a rotary laser positioning system developed at Tohoku University for full-resolution subsurface imaging. In this paper we will show how the high density 3-D GPR data acquired over an area of about 14 m?×?28 m can improve the image quality and reveal the subsurface archaeological structure of early dynastic foundations in the Saqqara area. The GPR vertical cross-sections and the horizontal depth slices extracted from the full-resolution 3-D GPR reveal great information about ancient human activities, most likely burial mounds. GPR data at depth greater than 1.3 m were overwhelmed by “ringing features” (repeated horizontal harmonic-like features) most probably caused by the presence of underlying shallow layers of low resistivity shale and claystone. A 2-D electric resistivity tomography (ERT) profile was acquired using a multi-electrode system with 1 m electrode spacing. The ERT section shows high resistivity for the near surface desert sand and gravel deposits. The second geoelectric layer detected by ERT shows a low resistivity value consistent with the presence of a highly conductive layer at a depth of about 1.3 m. Integration of such different geophysical tools (e.g. GPR with ERT) helps to interpret the repeated horizontal features in the 3-D GPR data.     

Three-dimensional laser interferometric CT (LICT) measurement of shock wave interaction around a circular cylinder

Three-dimensional (3-D) laser interferometric computed tomography (LICT) measurement has been applied to high-speed and unsteady flow including shock waves. The purpose of our investigation is to clarify 3-D flow phenomena quantitatively by using LICT. We used a diaphragm-less shock tube to clarify the unsteady shock wave behavior with the shot by shot method. The diaphragm-less shock tube enables us to obtain shock wave propagation reproduction in quick succession. By LICT the 3-D internal density structure of the shock–vortex flow field can be clarified. In this LICT method the observation system consists of a CCD camera, Mach–Zehnder interferometer, and nitrogen pulse laser as a light source with a suitable delay signal controller. The 3-D density CT data can be reconstructed typically from the 19 2-D density images which have a 5° interval among every shot of the diaphragm-less shock tube. As for the method to get many projection images, the optical system is fixed, while the model with a cylindrical duct and a cylinder is rotated by a fixed degree of intervals in the designated observation angle for every shot. In this paper the shock wave interaction with a finite length circular cylinder is observed by LICT measurement. For reconstruction of density distribution the Algebraic Reconstruction Technique (ART) is applied to reduce the artifact, together with precise observation.     

复杂轮廓曲面非接触三维数据测量的研究

介绍一种非接触式CCD三维数据测量仪，可对具有复杂轮廓的漫反射曲面进行测量、获取表面轮廓的三维数据，介绍了该仪器的测量原理、微机控制系统和误差分析。     

基于OPENGL的曲面零件三维图形系统开发

针对具有大规模数据点的曲面零件,提出了一种基于OpenGL的三维曲面零件实体的图形开发方法,有效解决了由大量三维数据点构建三维图形中所遇到的难题。上述方法已经成功应用于激光测量中的图形显示系统。     

Three-dimensional molecular distribution in single cells analysed using the digital imaging microscope

Cellular changes in molecular distribution are believed to underly a wide range of cell functions. In order to investigate changes in molecular distribution in single cells utilizing fluorescent probes we have developed a digital imaging microscope. The system, consisting of both hardware and software, automatically acquires 3-D data sets consisting of optical sections and then processes such data to facilitate the analysis of molecular distribution in single cells. The first major step in processing reverses distortion introduced principally by the optics of the fluorescent microscope. Various procedures for accomplishing this task are compared and a method based on regularization theory is shown to give superior results for several different 3-D images. Following this step features of interest are automatically extracted from 3-D images utilizing an artificial 3-D visual system. This artificial visual system utilizes a system of spatial filters to identify regional characteristics of images, the information obtained from these filters being used to identify and characterize clusters of molecules within the image. This information is then utilized to construct a 3-D graphical model of molecular distribution in single cells. Such models are displayed in 3-D and may be further analysed utilizing interactive 3-D computer graphics. These methods are illustrated by results obtained regarding alpha-actinin distribution in single smooth muscle cells.     

Development of in-process visualization system for laser-assisted three-dimensional microfabrication using photocatalyst nanoparticles

Recently, microfabrication technology has been used to develop micro-electro-mechanical systems (MEMSs), micro-total analysis systems (μ-TASs), and photonic crystals. Various microfabrication techniques have been proposed; however, a technique that can be used to efficiently fabricate 3-D structures via a simple procedure has not been reported thus far. Because 3-D metal structures have not only mechanical functions but also electromagnetic functions, it is desirable to develop such a technique. Our research group is in the process of developing a new technique for 3-D microfabrication that involves the use of a lower power continuous wave laser. Our technique is characterized by the reduction of silver ions via the photocatalysis of titanium dioxide (TiO2) excited at the laser beam waist. For the analysis and development of our microfabrication technique, we developed a microscope system that enabled us to observe the microfabrication process along the fabrication beam optical axis and its radial direction. We successfully visualized the microfabrication process in 3-D. The visualization showed that when the beam waist was swept, the silver structure grew in 3-D following its path. The effect of the substrate on the deposition condition was examined.     

汽车模具复杂棱脊和沟槽的数字化及激光加工轨迹规划

针对大型汽车冲压模具复杂棱脊和沟槽的数字化问题提出了三维自适应测量算法。为适应于激光表面强化加工的特殊要求,在后续测量数据处理过程中建立了复杂棱脊和沟槽的简化数学模型,提出了六维激光加工轨迹规划算法,并进行了测量和加工试验验证。上述算法都已应用到集成化柔性激光加工系统中。