一种高制动效率大角度硅扭转微镜MEMS光开关的设计

提出了一种利用静电力制动扭转梁带动微镜旋转,从而实现二维开关功能的MEMS光开关.使用ANSYS和COVENTOR软件对器件结构进行了模态、静态和瞬态分析,并对微镜制动梳齿的位置、器件的尺寸和扭转梁结构进行了优化.通过在微镜下方设计大空腔实现微镜90°的大角度扭转,使用新型衬底梳齿和结合扭转梁设计实现高静电制动效率,将制动电压降至18V.引入背面梳齿提高开关响应速度,模拟结果表明,光开关具有毫秒量级响应时间.与其他设计相比,该设计的微镜具有扭转角度大、制动效率高且开关速度较快的优点.     

高速窄带多光谱成像系统光谱重建技术研究

光谱成像技术可以同时从光谱维和空间维上获取被测目标的信息，即结合了空间成像系统和光谱检测系统的功能，因此近年在影像获取与处理领域中倍受重视。本论文基于窄带多光谱成像技术建立八通道CCD多光谱成像系统，它能够实时采集八个通道的图像，获得波长分布从可见到红外（420-940nm）八个波段的光谱响应值。在此基础上对图像进行位置配准、反射率定标、采用插值算法获得其它波段光谱响应值，最终能够获取图像中任意一点的光谱反射率及颜色参数。实验结果表明，本文使用的三次样条插值法对原始光谱图像进行平滑操作的方法是有效的，能够以一定精度模拟出目标物点的真实光谱特性。该系统在动态目标检测识别、艺术品评价复制等领域有着广阔的应用前景。     

基于DMD光刻制作微柱透镜阵列分模曝光的研究

针对无掩模光刻技术制作微柱透镜阵列的面形精度问题,对曝光方式和掩模设计进行研究,采用一种分模曝光方法,包括图形分层,掩模设计,分层掩模灰度调制,分层曝光四个步骤。在曝光前,需要对二维掩模版图按设计结构高度进行分层,以实现单层掩模在抗蚀剂上的投影成像高度不超过物镜的焦深范围。基于数字微镜阵列对灰度掩模的空间调制原理,设计出匹配的分层掩模版图,给出了图形分层原则和方法以及模板设计的原理。实验结果表明:采用该方法制作微柱透镜阵列,面形平均误差为0.54μm,相比以往单模曝光平均误差值0.79μm,平均误差减小了0.25μm,该方法弥补了由物镜焦深限制所造成的技术问题,提高了曝光质量。     

利用空间填充曲线和灰度分布估计的声图分割

针对声图中的目标分割问题,提出了一种利用空间填充曲线和灰度分布估计的声图目标分割方法。该方法首先利用空间填充曲线将声图由二维矩阵变换为一维向量;其次在一维空间下进行滤波、灰度分布估计、阈值计算、分割处理;最后将分割后的一维向量逆变换为二维矩阵,得到目标分割结果。实际的声图处理验证了方法的有效性。     

基于数字式二维自准直仪的转台角位置误差校准时的影响因素分析

采用自准直仪结合多面棱体对转台的角位置误差进行校准是工作中普遍使用的方法。数字式二维自准直仪具有极高的精度和分辨力,被越来越多的应用在角位置误差校准场合。本文总结了实际工作中累积的经验,分析了用数字式二维自准直仪结合多面棱体校准转台的角位置误差时的几个影响因素,做了公式推理和试验验证,并提出了相应的解决方法。     

基于时空级联自适应的多频信号混响抑制方法

针对使用多频信号的高速运动的前视主动声纳,对运算量小、较为实用的降维空时自适应抑制混响方法进行了研究,分析得出多频信号的混响空时二维分布特性,在此基础上提出了基于时空级联自适应处理非相干叠加多频信号混响抑制方法,仿真实验研究表明：该方法具有较好的多频信号混响抑制性能,而且大大降低了系统的维数和运算量,便于实际工程实现。     

加权稀疏信号重构的近场源定位方法

针对近场源定位问题,提出了一种使用加权L1范数优化进行稀疏信号重构的近场源定位方法。该定位方法分步完成目标的方位和距离估计。为了避免二维优化问题出现,首先利用均匀线阵的对称特性,通过菲涅尔近似,将二维参数估计的近场定位问题转换为类远场阵列的一维参数估计问题,接着将该一维参数估计问题转换为稀疏信号重构问题,通过类MUSIC权向量的构造,使用加权L1范数优化方法重构稀疏空间谱得到目标波达方向;在得到信号波达方向之后,再利用稀疏信号重构的思想求解信号源到阵列的距离。最后,通过数字仿真验证了算法在估计精度和分辨率等方面的优良性能。     

基于遗传算法和拓扑优化的结构多孔洞损伤识别

鉴于拓扑优化和遗传算法在结构损伤识别中各自的优点,本文将遗传算法、有限元和拓扑优化三种方法相结合,提出了一种用于二维结构多损伤识别的新方法。这种方法将拓扑优化的设计变量和遗传算法的参数统一化,将拓扑优化中的目标函数和约束方程与遗传算法的适应度函数联系起来,并以拓扑优化的约束方程作为控制条件参与整个遗传运算的控制。采用二进制编码遗传算法代替连续变量拓扑优化的方式对发生孔洞损伤形式的二维结构进行损伤识别,避免了利用连续变量拓扑优化进行损伤识别时参数阈值的确定可能给识别结果带来的不良影响。通过对两个二维结构模型的多损伤识别仿真计算,结果显示本方法能够很好地识别二维结构中多个位置的损伤,对于仅用拓扑优化法很难识别的轻微孔洞损伤情况,该方法也能得出与实际情况吻合良好的结果。     

FRM滤波器中应用积分梳状滤波器的研究

传统的频率响应屏蔽(Frequency Response Masking,FRM)滤波器由多个含有乘法器的滤波器构成,计算复杂度较高。提出了一种改进窄带低通FRM数字滤波器设计复杂度的方法,使用积分梳状滤波器作为屏蔽滤波器,以达到设计窄过渡带的滤波器的要求。仿真结果表明,在降低窄带低通FRM滤波器计算复杂度方面效果明显,有效地减少了乘法器的使用,降低了目标滤波器设计的阶数。该方法可以应用于窄过渡FRM数字滤波器的设计中。     

激光影院有望成为现实

中科院光电研究院和北京中视中科光电技术有限公司近日宣布,他们已成功利用激光作为数字放映机光源实现了大银幕放映。这个团队使用了激光和MEMS（Micro-Electro—Mechanical Systems,微机电系统）技术。他们相信这将成为未来新一代的电影放映技术,这台激光放映机采用红绿蓝激光取代目前数字放映机中的自光和滤色镜,将激光打在德州仪器（TI）生产的MEMS数字微镜器件（DMD）上。这个器件由数百万个微镜组成,每个微镜对应银幕上的每个像素,芯片靠调节微镜方向来控制像素的打开和关闭。     

Static response and free vibration of two-dimensional functionally graded metal/ceramic open cylindrical shells under various boundary conditions

The free vibration and static response of a two-dimensional functionally graded (2-D FGM) metal/ceramic open cylindrical shell are analyzed using 2-D generalized differential quadrature method. The open cylindrical shell is assumed to be simply supported at one pair of opposite edges and arbitrary boundary conditions at the other edges such that trigonometric functions expansion can be used to satisfy the boundary conditions precisely at simply supported edges. This paper presents a novel 2-D power-law distribution for ceramic volume fraction of 2-D FGM that gives designers a powerful tool for flexible designing of structures under multifunctional requirements. Various material profiles in two radial and axial directions are illustrated using the 2-D power-law distribution. The effective material properties at a point are determined in terms of the local volume fractions and the material properties by the Mori–Tanaka scheme. The 2-D generalized differential quadrature method as an efficient and accurate numerical tool is used to discretize the governing equations and to implement the boundary conditions. The convergence of the method is demonstrated, and to validate the results, comparisons are made with the available solutions for FGM cylindrical shells. The interesting results indicate that a graded ceramic volume fraction in two directions has a higher capability to reduce the mechanical stresses and natural frequency than conventional 1-D FGM. The achieved results confirm that natural frequency and mechanical stress distribution can be modified to a required manner by selecting an appropriate volume fraction profile in two directions.     

Three-dimensional simulation of near-infrared diffusion in tissue: boundary condition and geometry analysis for finite-element image reconstruction

Imaging of tissue with near-infrared spectral tomography is emerging as a practicable method to map hemoglobin concentrations within tissue. However, the accurate recovery of images by using modeling methods requires a good match between experiments and the model prediction of light transport in tissue. We illustrate the potential for a match between (i) three-dimensional (3-D) frequency-domain diffusion theory, (ii) two-dimensional diffusion theory, (iii) Monte Carlo simulations, and (iv) experimental data from tissue-simulating phantoms. Robin-type boundary conditions are imposed in the 3-D model, which can be implemented with a scalar coupling coefficient relating the flux through the surface to the diffuse fluence rate at the same location. A comparison of 3-D mesh geometries for breast imaging indicates that relative measurements are sufficiently similar when calculated on either cylindrical or female breast shapes, suggesting that accurate reconstruction may be achieved with the simpler cylindrical mesh. Simulation studies directly assess the effects from objects extending out of the image plane, with results suggesting that spherically shaped objects reconstruct at lower contrast when their diameters are less than 15-20 mm. The algorithm presented here illustrates that a 3-D forward diffusion model can be used with circular tomographic measurements to reconstruct two-dimensional images of the interior absorption coefficient.     

分舱段圆柱壳声散射数值和试验研究

基于有限元方法建立了填充不同介质的有限长分舱段圆柱壳声散射数值计算模型,仿真了填充空气-空气、空气-水、水-水三类两舱段圆柱壳声散射特性,并完成了三类两舱段圆柱壳体声散射试验,获取和分析了两舱段圆柱壳体声散射的时间角度谱和频率角度谱特性。利用物理声学方法分析了壳体表面、端面以及内部填充水介质对散射声场的影响,揭示了两舱段圆柱壳声散射频率角度谱中呈现的干涉条纹特征形成机理,为水下分舱段目标,如水下无人航行器的主动声呐探测和识别提供理论支撑。     

3-D measurements using a video camera and a range finder

The geometric modeling of the environment can be carried out by incorporating a video camera range finder. When the quality of images is poor, the range finder, which is mounted on a site and azimuth rotation turret, brings an indispensable complement by measures of depth. The purpose of this paper is to build a geometric database of a three-dimensional (3-D) world in telerobotic applications. The calibration of the sensor system is presented by focusing on models of the range finder and methods we studied to determine them. The experimental results allow the evaluation of models and methods in terms of accuracy and stability. We show how the problem of setting up the 3-D geometric database can be solved by cooperation between human operator and sensors. Two cases are treated for database updating: determining the right position of known objects and inserting an embodying volume to model unknown objects, The experimental results concerning object modeling of cylindrical and polyhedral pattern and are given in terms of volume dimensions and position errors     

Quasi-three-dimensional method of moments for analyzing electromagnetic wave scattering in microwave tomography systems

A new quasi-three-dimensional method of moments (Quasi-3-D MoM) for analyzing electromagnetic wave scattering from a cylindrical dielectric object surrounded by a dipole array in microwave tomography systems is presented in this paper. A wire-volumetric electric field integral equation is derived for the electromagnetic wave scattering phenomena in microwave tomography systems. The new method is based on the MoM and involves rectangular cylindrical cells modeling the cylindrical object. The distribution of electric flux densities along the axial direction of cylindrical cells is expanded as a Fourier series multiplied by an attenuation factor, which is one part of basis functions. Therefore, the Quasi-3-D MoM is performed in a two-dimensional discretization, and the computational complexity is reduced. Detailed mathematical steps along with some numerical results are presented to illustrate the efficacy and accuracy of this approach.     

From 3-D Sonar Images to Augmented Reality Models for Objects Buried on the Seafloor

The investigation of man-made objects lying on or embedded in the sea floor can be carried out with acoustic imaging techniques and subsequent data processing. In this paper, we describe a processing chain that starts with a 3-D acoustic image of the object to be examined and ends with an augmented reality model, which requires minimal user involvement. Essentially, the chain includes blocks devoted to statistical 3-D segmentation, semi-automatic surface fitting, extraction of measurements, and augmented reality modeling. In particular, the 3-D segmentation method presented here is based on a volume-growing approach, which is essentially a 3-D extension of the traditional 2-D region growing. The volume-growing operation is guided by a statistical approach based on the optimal decision theory. The surface-fitting block is based on predefined geometric models, i.e., one of them is tentatively selected by the user after a preliminary study of the segmented object and is automatically or partially manually adapted to the segmented data by exploiting an inertial tensor. The proposed chain was successfully applied to the analysis of some 3-D acoustic images obtained from both simulated and real signals acquired by different sonar systems and containing objects that were completely or partially buried. The segmentation results provided an effective help in the identification of the object's shape, i.e., facilitating the subsequent surface-fitting step and the extraction of related measurements.     

考虑三维圆柱铰间隙碰撞的空间机构柔性多体动力学分析方法

三维圆柱铰的动态性能对空间机构的运动精度和动力学特性有着重要的影响。基于多体动力学方法和刚体有限元方法,提出考虑三维圆柱铰的间隙碰撞和动态接触作用的空间机构柔性多体接触动力学方法。采用圆柱-圆柱的线接触力学模型和切片法,计算圆柱-圆柱的接触变形量和接触力,建立三维圆柱铰的轴销与轴套之间的间隙碰撞作用和三维动态接触关系。以等效刚体单元和Timoshenko梁单元描述柔性杆件的刚性有限元模型,建立柔性连杆和三维圆柱铰的具有多刚体系统的统一形式的动力学方程。计算分析了含三维圆柱铰的空间机构的运动精度和动力学特性,获得空间机构的位移响应,三维圆柱铰的相对运动轨迹和动态作用力等动力学响应。采用三维圆柱-圆柱动态线接触方法,能有效地预测空间机构系统的三维圆柱铰持续接触、间隙碰撞状态和摩擦作用下的动力学特性。计算结果表明三维圆柱铰的间隙碰撞作用对空间机构的运动精度和动态特性的影响较为显著。动力学模型和计算结果对复杂工况下高精度多间隙的空间机构的动态设计和动力学研究具有重要的理论意义。     

复合材料叠层圆柱曲板振动分析的半解析解

用三维弹性理论求解复合材料叠层圆柱曲板问题。在圆柱坐标系中，将三维弹性理论表述成哈密顿形式体系，得到一个变分原理，然后有限元法，给出一种半解析解，克服了过去完全的解析解及基于二维近似理论的数值解的不足。数值算例表明本文的方法是有效的。     

Semi-three-dimensional algorithm for time-resolved diffuse optical tomography by use of the generalized pulse spectrum technique

Although a foil three-dimensional (3-D) reconstruction with both 3-D forward and inverse models provide, the optimal solution for diffuse optical tomography (DOT), because of the 3-D nature of photon diffusion in tissue, it is computationally costly for both memory requirement and execution time in a conventional computing environment. Thus in practice there is motivation to develop an image reconstruction algorithm with dimensional reduction based on some modeling approximations. Here we have implemented a semi-3-D modified generalized pulse spectrum technique for time-resolved DOT, where a two-dimensional (2-D) distribution of optical properties is approximately assumed, while we retain 3-D distribution of photon migration in tissue. We have validated the proposed algorithm by reconstructing 3-D structural test objects from both numerically simulated and experimental date. We demonstrate our algorithm by comparing it with the calibrated 2-D reconstruction that is in widespread use as a shortcut to 3-D imaging and proving that the semi-3-D algorithm outperforms the calibrated 2-D algorithm.     

Research on Torque Calculation Method of Permanent-Magnet Spherical Motor Based on the Finite-Element Method

In this paper, the finite-element method (FEM) is used to calculate the spinning torque of the permanent-magnet (PM) spherical motor. Three-dimensional (3-D) FE model of the PM spherical motor is established. Spinning torque distribution on the spherical surface and its variation curve on the equator are obtained respectively. In order to avoid the complicated torque calculation process under 3-D magnetic field and thus reduce the computational burden, the torque calculation method based on the 2-D conversion model is proposed. This method equivalently simplifies the magnetic field of the spherical PMs and the shape of cylindrical stator windings to be simulation parameters of the 2-D conversion model. With these parameters, 2-D conversion model of the PM spherical motor is established. Spinning torque variation curves obtained by the 3-D model and the 2-D conversion model respectively are compared and the results agree extremely well. By comparing the maximum static torque (MST) obtained under different configuration parameters of the PM spherical motor, it is found that the errors are within the allowable range. Therefore, the reliability of the proposed torque calculation method in the paper is verified. Finally, based on the 2-D conversion model, variation curves of the MST with the length of the air gap, the ampere turns, the length of stator windings and the outer radius of stator windings are obtained, and they are validated by those based on the 3-D model. These results can provide the basis for the optimization of the PM spherical motor.