脉冲超声换能器声场测试系统的设计*

脉冲超声换能器是超声检测的关键部件,为了获取其声场特性参数,文中基于小球反射法原理,采用虚拟仪器技术和单片机技术设计了声场测试系统。系统的程控交互界面采用了美国国家仪器公司研制开发的图形化编程软件LabVIEW来设计,在程控交互界面程序中通过调用动态链接库DLL来对系统核心硬件超声发射接收卡进行数据通信及对卡功能进行设置,同时系统上位机通过RS232串口与下位机单片机通讯,实现对三轴扫查平台的多种扫查方式控制。该系统可实时显示脉冲换能器声压分布图像,并可通过对声压分布数据实现对换能器近场长度及扩散角等参数的测量。     

面向电容式微机械超声换能器器件的32通道收发 电路设计与测试*

针对以电容式微机械超声换能器(CMUT)阵列为探头的超声成像系统,设计了一种兼具现场可编程门阵列(FPGA)控制、脉冲驱动以及微弱电流信号检测功能的电路。利用FPGA产生64路控制信号,控制脉冲信号的频率、脉冲个数、占空比等参数;脉冲电路在FPGA以及直流电压的控制下,产生32路脉冲信号;接收电路通过跨阻放大结构实现32路电流信号检测;32通道收发电路利用脉冲产生芯片内自带的T/R开关进行高压隔离。通过搭建测试平台,对收发电路功能及一致性进行测试,并连接CMUT进行自发自收测试。测试结果表明,32通道收发电路具有良好的一致性,电路可以实现基于CMUT阵列的32通道超声信号的发射,检测回波信号,并对CMUT器件的带宽进行测试。电路具有功能完善,结构稳定的优点,为基于CMUT阵列的超声成像系统的应用提供了硬件支持。     

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采用了通用高速A/D采集器采集信号数据,用软件的方法开发出了具备多道能谱脉冲识别和计数分析能力的软件.用此软件实现了每次托卡马克放电后,在较短的时间内从庞大的原始采集数据中提取出能谱脉冲数据,计算和显示能谱图,这为下一步测量电子温度打下了基础,并同时实现了数据共享.     

基于Labview的脉冲漏磁检测系统的研究

研究了一种脉冲信号激励的漏磁检测系统;利用USB数据采集卡I/O口输出脉冲方波信号经过功率放大环节生成激励信号,通过数据采集卡触发采样功能实现检测信号的同步采样;基于Labview软件搭建了漏磁检测虚拟仪器平台,实现了漏磁检测信号的采集、调理、储存、回放和分析功能;通过实验对加工有宽度为2 mm深度分别为2 mm、5 mm、10 mm的3个裂纹缺陷的钢样本进行检测,应用霍尔传感器检测漏磁场信号;检测信号经过调理和采集,在电脑中实时显示漏磁信号随时间的变化波形;通过分析回放采样信号的峰值和峰值到达时间评估缺陷的位置和深度;实验结果表明缺陷深度越大采样信号的峰值越大,峰值到达时间越长。     

ER-200D-SRC型EPR谱仪微机系统的改造

详细叙述了德国BRUKER分析仪器公司ER-200D-SRC型EPR谱仪与IBM PC/386微机联机的软硬件系统,该系统综合了仪器的自动磁场扫描控制,数据采集累加和数据分析处理及数据绘图、打印等各项功能。其硬件由IBMPC/386微机及二大接口模块组成。一块为商品化的12位A/D、D/A接口卡,另一块为自行设计的以INTEL-8255可编程通用接口电路为主体的数字量输入输出控制接口卡,可分别独立地插入PC机的扩展槽中,其软件采用C语言编写,具有菜单式、结构化、模块化、汉字工作提示、实验数据实时屏幕绘图、实验参数实时显示等特点,用户界面良好,该系统恢复并提高了原谱仪的整体性能,具有一定的推广价值。     

基于PCI总线特快信号测试卡的设计

图1为基于PCI总线的特快信号测试卡系统构成框图。特快信号测试卡硬件由特快信号解调芯片、双口RAM、PCI用户接口逻辑和$5933构成。特快信号测试卡软件由驱动应用程序、事后储存处理和实时监控构成。特快信号解调芯片完成特快信号的检测和实时存储，主要包含单次宽脉冲组SWPG信号源、PPK信号源、特快信号译码、特快信号地址形成、特快信号时序控制、特快：信号记录数据形成、PPK检帧同步、自适应禁存控制、相对时电路、时间记录地址形成、时间记录数据形成等电路，     

基于PC机的一种多功能声显微镜及可视化技术的研究

近来研制成功了一种基于ＰＣ机、我们称为“ＴＨＳＡＭＭ”型的多功能声显微镜。在ＰＣ机内插入采样率１ＧＳＰＳ的超高速Ａ／Ｄ卡和信号产生和接收卡,利用软件完成信号检测、处理、显示功能。仪器工作频率为１－１００ＭＨｚ;在检测样品时,同时多层显示Ａ、Ｂ、Ｃ扫描结果。根据声学理论、Ｍａｒｃｈｉｎｇ Ｃｕｂｅ等值面抽取方法和ＯｐｅｎＧＬ技术完成了三维数据的可视化处理,显示样品的内部三维结构。该系统已成功应用于多     

基于AC6412脉冲计数卡的自动条纹识别

本文主要介绍了通过一光电系统产生电信号,从而把电信号转化为AC6412脉冲计数卡可以识别的脉冲信号,实现条纹的计数功能.     

基于DSP+FPGA的实时信号采集系统设计与实现

为了提高对实时信号采集的准确性和无偏性,提出一种基于DSP+FPGA的实时信号采集系统设计方案。系统采用4个换能器基阵并联组成信号采集阵列单元,对采集的原始信号通过模拟信号预处理机进行放大滤波处理,采用TMS32010DSP芯片作为信号处理器核心芯片实现实时信号采集和处理,包括信号频谱分析和目标信息模拟,由DSP控制D/A转换器进行数/模转换,通过FPGA实现数据存储,在PC机上实时显示采样数据和DSP处理结果。通过仿真实验进行性能测试,结果表明,该信号采集系统能有效实现实时信号采集和处理,抗干扰能力较强。     

超声成像实验仪

我们模拟了一个原理相对容易、结构相对简单的超声成像实验。通过超声波测试仪发射和接收换能器信号 ,输出的电压信号送入计算机的A/D卡。A/D卡的另一通道采集换能器的跃变位置信息 ,并将数据提供给成像程序 ,把物体某一断层的截面图画出。通过这一实验 ,我们可以了解超声波在固 /液两相流中的传播原理 ,同时也可掌握数据采集和一般的成像方法     

All-optical adaptive scanning acoustic microscope

We have constructed a fast laser-based surface acoustic wave (SAW) microscope, which may be thought of as a non-perturbing scanning acoustic microscope. The instrument is capable of rapid high resolution vector contrast imaging at several discrete frequencies, without any damage to the sample. Tailoring the generating optical distribution using computer-generated holograms allows us to both focus the acoustic waves (increasing their amplitude) and to spread the optical power over the sample surface (preventing damage). Accurate quantitative amplitude and phase (velocity) measurements and unique acoustic contrast mechanisms are possible with our instrument based on this technology due to the non-perturbing nature and the instrument geometries.However, the complexity of the optical generation profile leads to a strong dependence on material properties such as the SAW velocity and material anisotropy. We address these issues in this paper, and demonstrate how a spatial light modulator may be used to adapt the generating optical distribution to compensate for the material properties. This facilitates simpler alignment and velocity matching, and, combined with an acoustic wavefront sensor, will allow real-time adjustment of the generating source to enable imaging on anisotropic materials.     

The elastic microstructure of various tissues

Previous work has indicated that a modified Quate-Lemons scanning acoustic microscope (SAM) is capable of measuring the acoustic propagation properties of sections of biological tissue. The lens is excited by an impulse, rather than a tone burst, and the undemodulated returning signal from the tissue is recorded. The variations in received signal with time are used to deduce the sound speed, attenuation, impedance, and section thickness. In this article, the technique is applied to various types of tissue, and the variations in acoustic propagation properties are computed. Conventional tone burst SAM images at 425 MHz are compared with the time resolved data in order to elucidate the contrast mechanisms. The effects of varying the frequency and position of the focal plane on the tone burst images are interpreted in the light of the broadband results.     

基于声学扫描振镜的超声/光声双模态成像技术

超声/光声双模态成像技术因其同时兼具超声的高分辨率结构成像和光声的高对比度功能成像优势,极大地推动了光声成像技术的临床应用推广.传统超声/光声双模态成像技术多基于超声成像所用阵列探头同时收集光声信号,系统结构紧凑且无需图像配准,操作便捷.但该类设备使用阵列探头和多通道数据采集,使得其成本较高;且成像结果易受通道一致性差异影响.本文提出了一种基于声学扫描振镜的超声/光声双模态成像技术,该技术采用单个超声换能器结合一维声学扫描振镜进行快速声束扫描,实现超声/光声双模态成像,是一种小型化、低成本的双模态快速成像技术.本文开展了系列仿体和活体成像研究,实验结果表明:系统有效成像范围为15.6 mm,超声和光声成像B扫描速度分别为1.0 s^–1和0.1 s^–1 (光声成像速度主要受制于脉冲激光器重复频率).基于本文所提技术研究,有助于进一步推动超声/光声双模态成像技术的临床转化和普及;也为基于超声信号检测的多模态成像技术提供了一种低成本、小型化和快速声信号检测的参考方案.     

Data acquisition and instrument control system for neutron spectrometers

A personal computer (PC)-based data acquisition and instrument control system has been developed for neutron spectrometers in Dhruva reactor hall and Guide Tube laboratory. Efforts have been made to make the system versatile so that it can be used for controlling various neutron spectrometers using single end-on detector in step scan mode. Commercially available PC add-on cards have been used for input-output and timer-counter operations. An interface card and DC motor driver card have been developed indigenously. Software for the system has been written in Visual C++ language using MS Windows operating system. This data acquisition and instrument control system is successfully controlling four spectrometers at Dhruva reactor.     

声透镜对多层样品的光声层析成像

由于光声效应产生光声压分布图像,所以当强散射介质中的模拟吸光组织在受到短脉冲激光照射时,该声压分布会经声透镜成像在像平面上。在像平面上利用线性超声探测器阵列获取光声信号并传递给高速数据采集卡进行数据采集,可由程序重构出光声图像。设计的光声层析成像系统可以采集记录一定深度的数据,成像时只要在所采集到的数据中选取不同列数即可同时获得强散射介质多层样品不同层面的光声图像。实验成功地获得了强散射介质内多层样品不同层面的光声层析图像。该成像方法无需进行复杂的算法重建,且可以同时实现多层样品不同切面的光声成像。     

Real-time electro-optical heterodyne signal processors

A cross-correlation function of two time-varying signals and two spatial signals is considered analytically for real-time signal processing. An electro-optical heterodyne signal processor with a set of two successive ultrasonic light modulators and two optical masks is simply used because this optical system is not so sensitive in its alignment as conventional Mach-Zehnder-like interferometers for photomixing. As two special cases, a convolution function of two rectangular pulses fed to both the modulators and a correlation function of a rectangular pulse, fed only to one of the modulators, with a rectangular aperture made in one mask are produced experimentally for verification.     

Reconstruction of the time dependence and signal parameters of far-field extended wideband sources: Part 1. Reconstruction techniques and technical instruments

The problem of reconstructing the time dependence of an extended source in the far zone is considered. It is shown that the time dependence of the source signal is reconstructable in the far zone during acoustic signal recording with a far-field array and in further processing. In this work, possible signal disturbances due to the finiteness of the receiving aperture are estimated and optimal parameters of the signal processing system are determined. A linear array is suggested in the form of digital receiving elements that synchronously record the acoustic field in a band of up to 10 kHz and transfer the received signal through four twisted pairs directly to a PC network card. The technique described in the work and its technical implementation can be used in hydroacoustic measurements and in designing sound-recording systems for orchestras and large choirs.     

Processing an acoustic microscope’s spatiotemporal signal to determine the parameters of an isotropic layer

This paper presents a method for measuring the thickness and velocities of body waves and the density of an isotropic layer by a pulse scanning acoustic microscope. The method is based on recording the microscope signal as a function of the displacement magnitude of the focused ultrasonic transducer along its axis perpendicular to the sample surface and on the decomposition of the recorded 2D spatiotemporal signal into the spectrum of plane pulse waves. The velocities of the longitudinal and transverse waves and the layer’s thickness are calculated from the relative delays of the components of the spectrum of plane waves reflected from the surfaces of the layer and the density is computed by the amplitudes of these components. An experimental investigation of a test sample in the form of a glass plate carried out in the 50-MHz range shows that the error in measuring the thickness and velocities of body waves does not exceed 1% and the density measurement error does not exceed 10%.