Radiation Acoustic Field of a Linear Phased Array on a Cylindrical Surface

A new linear ultrasonic phased array fixed on a cylindrical surface is designed. This kind of the cylindrical phased array can meet the specific requirements of the application in testing pipe quality inside pipes. Using the transducer, we can not only avoid mechanical rotating but also test the quality of any point in a pipe by ultrasonic phase array technology. The focused acoustic field distributions in the axial, radial and tangential directions of the transducer are investigated theoretically by numerical simulation. The energy flux density, the width of the main lobe, the imaging resolution, the grating lobe elimination and other characteristics are analysed. The effect of the focal distance, effective aperture, transducer radius, number of total element, and steering angle on the acoustic field distribution is also studied.thoroughly. Many important results are obtained.     

Photonic Architectures for Broadband Adaptive Nulling with Linear and Conformal Phased Array Antennas

This paper presents several photonic architectures for independently steering multiple broadband nulls for linear and conformal phased array antennas. Analytic expres sions that quantify bandwidth requirements are developed and both experimental and simulation results which demonstrate the antenna system performance are presented. In a fully integrated, optimized system, null depths in excess of 50 dB across a multigigahertz bandwidth are anticipated and the critical factors that influence this performance are examined.     

二元位相校正技术在相控列阵光学系统中的应用

提出一种使用二元光学器件实现位相校正的新方法。在子孔径拼接的相控列阵光学系统中，采用二元光学器件二元位相校正板对子孔径拼接后产生的残留波像差进行校正，既达到位相校正技术要求，又大大简化系统结构并减小了系统的尺寸和重量。所制作的二元器件具有８个台阶，套刻精度达到２μｍ，并使残留波像差降为原来的一半。     

基于多元线性阵列探测器的快速光声层析成像

报道了一种基于相控聚焦的多元线性阵列探测器进行快速光声层析成像的方法和装置,并实现了模拟组织的光声层析成像。实验中采用波长为532nm脉宽为7ns的倍频Q-YAG激光器作为激发光源。多元线性阵列探测器由320个振元组成,采用相控聚焦的方法成像,每次由11个振群的探测器接受信号并合并1路,一幅图像由64路这样的信号组成。实验结果能够正确反映样品中的光学吸收分布。与现有的方法比较,本系统具有快速方便的特点,它有望成为一种组织功能在体成像的新方法,发展成为一种低成本的实用的临床诊断装置。     

基于线阵TDI-CCD器件的扫描成像系统设计

提出了由步进电机控制振镜运转,基于线阵TDI-CCD相机的扫描成像设计方案.通过研究线阵TDI-CCD器件的结构与工作原理,得到对振镜扫描速率和相机行扫描速率进行同步的方法,实现了空间位置配准.采用EC-11相机进行成像实验,扫描成像系统输出了可辨别的图像.     

Focusing of Divergent Cylindrical Waves and the Prospects for Borehole Acoustics

This paper discusses prospects for borehole acoustics associated with the use of focused fields. The possibility of developing efficient borehole methods for testing nonlinear characteristics of natural deposited geological environments is studied. The potential of improving geotechnological processes using focused fields induced by extended borehole antennas is considered. The results of a pilot experiment on acoustic-field stimulation of underground leaching of less-common metals are presented.     

直线阵光学综合孔径成像中的子孔径尺寸效应

光学综合孔径阵列中的子孔径的位置和直径的大小对成像质量有着重要的影响。详细分析了几种不同优化排列的光学综合孔径直线阵列的无像差点扩展函数、光学传递函数和衍射成像特性．结果表明,子孔径的位置不同．光学传递函数的空间频率覆盖有很大的差异。增大子孔径的直径可以增大空间频率覆盖程度．但子孔径直径过大时义会产生空间频率冗余度和增加制造成本。直线阵光学综合孔径的衍射成像是多重像,子孔径直径的增大还可以减小重影的程度,提高成像质量。结果说明,在进行光学综合孔径阵列优化排列时必须考虑子孔径的直径大小这个重耍的因素。     

Experimental Study of a Borehole Acoustic Radiator with a Ring in a Long Cylindrical Chamber

We have carried out an experimental study on the generation of pressure oscillations in a model of a borehole ring acoustic radiator that moved within a cylindrical chamber. The possibility of preserving a short jet with increasing resonator chamber length has been studied. The influence of the jet length, which is determined by the interval between the nozzle and the ring, on the frequency and intensity of generation has been considered. The constancy of the chamber resonance at the natural frequency, regardless of the length and velocity of the jet, has been noted. Recommendations for choosing the length of the chamber and the generation frequency associated with it are given.     

使用CPLD实现对DALSA4口输出线阵CCDIT-P1的驱动

本文分析研究了DALSA公司1024元4口输出线阵CCD IT-P1在驱动中存在的诸多问题.针对CCD IT-P1采用多口输出工艺、驱动频率要求高、驱动时序比较难于实现等问题,提出了使用CPLD(Complex Programmable Logic Device)器件结合硬件编程语言VHDL最终实现高频驱动的方法.与使用传统门电路实现高频驱动相比,该方法实现了大量门电路功能,解决了传统方法中大量高频门电路的干扰以及采购等问题,提高了驱动电路的集成化程度、抗干扰性能及可移植性能.实验表明,使用CPLD实现CCD的驱动无论在电路设计,还是在系统集成和抗干扰等方面都表现出良好的性能,使系统十分简洁,优化了整个驱动设计.     

基于环形相控阵的空心车轴探伤方法的研究

以高速列车空心车轴超声波探伤为背景,通过声场分析及CIVA软件仿真设计了环形相控阵,评估了有效阵元个数以及触发频率对声场的影响。采用环形相控阵探头的探伤系统能以直线推进的方式对空心轴进行探伤,较现有探伤方式,可大幅提升检测效率、简化机电结构,并可有效避免由于探头旋转所导致的耦合不稳定。     

新型液晶光学相控阵的特性研究

将液晶作为平板光波导的上包层,构建了液晶光学相控阵器件.根据Frank-Oseen液晶连续体弹性形变理论与光栅衍射理论,研究分析了基于这种新型结构下液晶光学相控阵的传输特性,输出衍射特性和其它性能特性.研究结果表明,器件的传输电控相位延迟可以实现更大的光程差;阵列电极周期数目、电极宽度、电极间隔宽度等结构参量对器件的输出衍射光束的光强分布和半峰值全宽度影响很大,同时光束扫描的可行性得到论证;器件的响应时间提高了一个数量级,且其色散性能获得改善.为以后研制新型液晶光学相控阵提供了理论基础与技术设计依据.     

Optimized Optomechanical Micro-Cantilever Array for Uncooled Infrared Imaging

We present a new substrate-free bimaterial cantilever array made of SiN_x and Au for an uncooled micro-optomechanical infrared imaging device. Each cantilever element has an optimized deformation magnification structure. A160×160 array with a 120μm×120μm pitch is fabricated and an optical readout is used to collectively measure deflections of all microcantilevers in the array. Thermal images of room-temperature objects with higher spatial resolution have been obtained and the noise-equivalent temperature difference of the fabricated focal plane arrays is given statistically and is measured to be about 270mK.     

光纤干涉成像阵列全息相位校正研究

针对光纤传输和干涉成像阵列中的相位误差, 提出了一种基于特殊光子晶体的全息相位校正方法。首先分析了光纤干涉阵列成像的基本原理和相位信息的传输过程, 以一维线性阵列建立成像系统相位误差模型, 通过对参考光束和探测器前的快门交替打开和闭合, 来分别实现在晶体上写入由光纤阵列的出射光束与参考光束干涉形成的含有相位误差的光栅函数, 和光纤中出射光束被该光栅衍射和相位偏移以消除相位误差, 从理论上分析了上述基于光子晶体的全息法相位校正原理。最后采用所建立的含有相位误差的干涉阵列进行成像仿真, 对未加校正、采用本文方法和采用冗余基线校正的结果进行了对比分析。     

Calculation of Noise at the Output of a Phased Antenna Array in a Randomly Inhomogeneous Waveguide

Radiophysics and Quantum Electronics - We develop models of the formation of additive sea noise and surface reverberation at the output of a phased vertical antenna placed in a plane-layered...     

Linear Theory of Free Electron Laser with a Plasma-Loaded Cylindrical Waveguide

The dispersion characteristics of plasma–loaded free-electron laser has been analyzed using linear fluid model. The device under consideration consists of the cylindrical metallic waveguide, completely filled with background plasma and a relativistic electron beam which passes through a helical wiggler magnetic field. The result predicts that reasonable plasma density tends to improve the growth rate of the low-frequency optical wave of FEL and causes an shiftup in the operating frequency, However it has little effect on the growth rate of the high-frequency wave. In the plasma–loaded FEL, for the FEL oscillator, it may be tuned by varying the plasma density; and for the FEL amplifier, the wider frequency bandwidth is gained. A critical density n ^c _p for the background plasma density is found.     

角反射器耦合的InGaAs应变层量子阱锁相列阵激光器的模式特性

采用反应离子刻蚀技术，设计、制备了一种角反射器耦合的１０单元ＩｎＧａＡｓ应变层单量子阱镇相列阵激光器。在高达４×Ｉｔｈ的工作电流范围内，获得了主单瓣远场输出，单瓣束宽最低达０．６４°，接近衍射极限。考虑了角反射器引入的纵模与侧模之间的耦合，及载流子注入引起的反折射率导引，用微扰理论作了模拟计算，表明角反射器耦合是锁相列阵的一种新的耦合机制；主瓣对应于同相锁定，支瓣是由周期性微扰引入的高阶本征模。     

Modeling of Focused Acoustic Field of a Concave Multi-annular Phased Array Using Spheroidal Beam Equation

A theoretical model of focused acoustic field for a multi-annular phased array on concave spherical surface is proposed.In this model,the source boundary conditions of the spheroidal beam equation(SBE) for multi-annular phased elements are studied.Acoustic field calculated by the dynamic focusing model of SBE is compared with numerical results of the O'Neil and Khokhlov-Zabolotskaya-Kuznetsov(KZK) model,respectively.Axial dynamic focusing and the harmonic effects are presented.The results demonstrate that the dynamic focusing model of SBE is good valid for a concave multi-annular phased array with a large aperture angle in the linear or nonlinear field.     

Experimental Study on Localization of Absorbers within Tissue Phantom Using a Simple Phased Array System

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