Study on application of complementary Golay code into high frame rate ultrasonic imaging system

The high frame rate (HFR) ultrasonic imaging system, which is developed with limited diffraction beams, constructs images at a high frame rate. However the rectangular imaging area, to some extent, restricts the far field imaging information. At the same time, by virtue of one transmission event for constructing image, the system suffers from low SNR. In this paper we present a computationally efficient method to construct sector mode image and to increase the SNR in HFR system. The method uses orthogonal complementary Golay coded excitation to realize two transmit and receive events. Each emission simultaneously transmits two plane waves with different transmission angle. Then according to Golay code orthogonality, the received echo signals related to different angles are isolated and used to construct two images of different imaging area by HFR method. Finally the two images are synthesized to one frame of sector mode image.     

Extract echo signal in HFR imaging system

Ultrasonic high frame rate (HFR) method was developed by Jianyu Lu in 1997. This method constructs images in frequency domain; the spectrum of space domain objects is calculated based on the spectrum of echo signals, and the image is obtained by using IFFT (inverse fast Fourier transform). Because of this imaging process, the echo signal from each individual scatterer cannot be obtained directly. In this paper, we present a method, which can pick up the echo signal of every scatterer in HFR imaging method. Computer simulation has been performed to verify our method. With the new method we have developed, many other imaging methods, such as Doppler blood flow and elastic imaging, can be easily combined with HFR method to give more information of the imaged objects.     

一种基于非衍射波的高帧率超声成像发射系统的研究

基于非衍射波的高帧率(high frame rate,HFR)超声成像的前提是发射阵列波(array beam)声场,但由于阵列波的正弦函数特征使对超声发射信号加权处理变得比较困难,导致了发射系统复杂.针对这一问题,本文提出一种有效的解决方案.基于傅里叶变换理论,从方波的能量成分主要集中在基波这一特性出发,采用单值方波对超声传感器发射信号进行加权,用一个功率信号源和简单的电子开关网络实现了HFR系统中所需要的发射电路.实验表明,这种方案对HFR的成像质量几乎没有什么影响,但大大简化了HFR成像系统,这为HFR超声成像方法在现有B超声系统上的实现提供了一个可行的方法.     

激光光刻中数字微镜器件关键技术研究

在无掩模激光光刻系统中,TI(Texa instrument,德州仪器)公司基于DLP(digital light processing,数字光处理)架构的DMD(digital micromirror device,数字微镜器件)系统已经得到应用,但是存在光刻图像质量和光刻速度无法提高等瓶颈.提出采用单片FPGA控制...     

基于FPGA的超高速线阵CCD信号采集系统的设计与实现

线阵CCD已广泛应用于在线检测、图像识别等系统,目前高帧率采集系统多在200~500Hz之间。高速线阵CCD采集系统,如1K甚至10KHz以上的采集要求,设计难度大,电路实现复杂,需要专用处理器,产品成本高,提出了一种采用并行高速FPGA驱动线阵CCD,通过常规分立元件完成模拟信号处理,实现数字信号实时传输的方案。该方案不仅简化了硬件设计上的难度,在同等性能情况下,可实现每秒万帧的高速采样,大幅度降低了成本。方案选用Altera FPGA作为控制核心,实现高速信号采集的同时,在片上实现一定的图像算法,不仅加速了图像处理速度,同时降低了计算机的处理压力。最后,本电路通过USB2.0接口,完成数据的实时传输。设计具有高帧率、高灵敏度、性能稳定,便携使用等特点,同时还有一定的通用性,已应用于一些光学系统中。     

用于油气管道智能封堵的电磁双向通信技术研究

相对于传统的管内带压开孔封堵技术,高压智能封堵技术具有很大优势,应用前景广阔。而管内外通信技术是研发智能封堵系统的关键技术之一。针对智能封堵现场干扰强、通信速率要求不高,而金属管道对高频信号衰减大的特点,提出了一种基于频率调制和频域解调的管内外超低频电磁双向通信方法,并研发了相应的通信系统。该系统采用两个不同频率的超低频电磁信号分别表示码元0和1;发射线圈在MCU软件控制下发射频率调制的电磁信号,接收线圈将电磁信号转换为电信号;该电信号经过滤波、放大和高精度A/D采集,得到数字信号;将该数字信号送入MCU,通过实时对该数字信号作DFT,并搜索信号DFT幅度谱的最大峰值所对应的频率,来实现信号的解调解码。通过实验室模拟试验,验证了所研制的管内外电磁双向通信系统可完成向管内智能封堵器正确发送指令,同时将管内封堵器的动作状态返回地面控制单元,从而可保证管内智能封堵作业的准确可靠。     

像增强器荧光屏亮度均匀性自动测试系统

像增强器荧光屏亮度均匀性是评价像增强器的重要指标，其测试是像增强器测试领域的重点与难点。本文介绍一套我们研制的像增强器荧光屏亮度均匀性自动测试系统，该系统使用图像采集与图像处理技术，做到了自动测试，并且使测量精度提高了一个数量级。文章首先介绍了像增强器荧光屏亮度均匀性定义与传统光学测试方法，然后从传统方法的缺陷入手，系统阐述了新系统的工作原理、系统构成、测量结果。文章的最后对新系统测试结果与目前常规使用的光学测量结果进行了比较，从而体现该系统的独特性与优越性。     

一种高精度图像采集系统的设计与特点

介绍了一种新型、高精度、实时伪彩色图像采集系统的原理、构成和特点。该系统采用１０ｂｉｔＡ／Ｄ转换器，使得高性能图像分析与处理成为可能。系统采样频率为１４．７５ＭＨｚ，对于标准ＰＡＬ制电视信号，可以保证采样后像素的横纵比为１∶１。由于采用最新ＥＰＬＤ编程技术，使得系统体积减小，可靠性显著提高。可输出标准ＰＡＬ制黑白全电视信号、ＲＧＢ分量彩色信号、Ｙ／Ｃ分量彩色信号及复合视频信号。该系统通过标准ＩＳＡ总线与计算机接口，帧存直接映射计算机内存地址空间，存取速度快。本系统特别适合于高精度的图像测量应用     

基于EMD-AWPP和HOSA-SVM算法的分布式光纤振动入侵信号的特征提取与识别

针对传统的信号处理方法无法有效区分不同振动入侵信号,提出一种基于EMD-AWPP和HOSA-SVM算法的振动信息特征提取与识别方法,用于解决分布式光纤振动入侵检测系统的高精度信号识别问题。处理不同振动类型时,该方法首先利用基于经验模态分解的自适应小波包处理算法,不仅对信号的低频部分进行了分解,而且对高频部分即信号的细节部分也进行了更好的时频局部化处理,改善了信号特征提取精度,减少传感信号异常值的影响; 其次采用高阶谱分析中的双谱和双相干谱,精确提取包含不同振动入侵信号类型的特征矢量; 最后在BPNN参比模型的基础上,用粒子群算法优化SVM的识别参数,使识别模型具有更强的自适应和自学习能力,克服了神经网络易陷入局部最优的不足之处,实现不同振动入侵信号的特征矢量识别。分析结果表明,针对不同类型的入侵源识别,该方法可以有效剔除随机噪声的影响,提取传感信息的特征矢量,降低异常值的影响,算法的预测类别与输出类别几乎一致,振动识别的精确率达到95%以上,识别效果明显强于BPNN网络的检测算法,提高了信息分析的准确性。     

CCD胶片点阵信息判读技术

本文论述了一种判读胶片点阵信息的新技术.CCD点阵信息判读技术采用面阵CCD实时采集点阵图象,并结合数字图系处理技术,使点阵判读达到了通用性强、误码率低、处理速度高的水平,同时系统结构简单、成本低.本文在分析CCD图象处理系统原理的基础上,重点讲述了点阵图象的处理方法.     

基于扩散滤波的多尺度分解和重构方法及应用初探

从各向异性PM方程出发,推导多维扩散滤波微分方程的离散格式及其稳定性条件,首次构建基于扩散滤波的多尺度分解和重构方法,给出两种具体实施方案及其关键步骤.地震资料应用表明,所提方法分解和重构信号的过程合理可靠,其中方案①的2D傅里叶波数谱能量随尺度的增加而远离谱中心点,其残差信号表现为高波数信号,在随机噪声压制中取得了较好的效果;方案②的2D傅里叶波数谱能量随尺度的增加而靠近谱中心点,其残差信号表现为低波数信号,在低频逆时噪声压制中取得了较好的效果.所提方法计算过程简单易实现,对于信号处理提供了一种多尺度分解和重构方法,在地震信号处理领域具有较高的应用价值.     

基于帧频信号的图像存储时序控制方法

针对长时间服役光学设备图像存储系统性能退化和可靠性降低的问题,设计了新的图像存储系统结构。提出了一种基于帧频信号的时序控制方法,以帧频信号为基准驱动系统软硬件工作,结合秒信号、帧频信号与串口时间生成绝对时间,实现了四路独立数据流的同步采集,通过两级缓存机制保证数据采集-打包-存储之间的速率冗余匹配,对图像转移时间误差进行了修正。检测结果表明,系统时序得到了有效控制,长时间采集存储数据稳定可靠不丢帧,时间同步精度优于1ms。     

Design of a very high frame rate camera based on an asynchronous CCD driving method

A very high frame rate camera is designed based on an innovative CCD driving method. The CCD driving method is mainly implemented on frame transfer CCDs. Asynchronous drive timing sequences are applied in the image and storage section of the CCDs. Several rows of the charge in the image section are binned onto the same row in the storage section, and there are the same number of images to be stored in the storage section before they are read out. Based on the new driving method, the frame transfer CCDs can work at a very high frame rate in acquiring burst images though the reading speed remains at a lower level. A very high frame rate camera is designed in this paper. The innovative CCD driving method is mainly of concern. An e2v's CCD60 is adopted in the camera system, whose full size resolution is 128×128, and the up most frame rate is 1000 Hz in the conventional CCD driving method. By using the presented method, the CCD60 based imager is capable of operating at up to 40000 frames per second (fps) at a recognizable resolution of 128×32. Comparing cameras using traditional binning and region of interest technologies, the frame rate is normally less than 5000 fps while the resolution is only 32 × 32 lett.     

利用变偏振光谱技术实现显微成像深度选择

在正交偏振光谱(OPS)微循环成像系统的基础上,提出了通过改变信号光的偏振态来实现成像深度的选择。传统的OPS系统利用的是正交线偏振光,只能获得图像在某一断层的二维信息,但作者通过控制系统起、检偏单元椭圆偏振光的椭圆度,可以在不进行机械扫描的情况下将成像光束聚焦在不同的断层,从而获得不同深度处的组织信息。构建的变偏振光谱成像系统将光源发射光谱与红血球吸收光谱相匹配,可以实现微血管的探测,且具有较高的信噪比。对一块含标记物的猪肉脂肪进行实验,并通过图像处理得到了对比度与信号光偏振态间的定量关系。实验结果表明：椭圆度由0°～45°增大,即从线偏振光向圆偏振光转变的过程中,对比度逐渐增大,可探测到的最大深度增大。最后利用该系统,对裸鼠耳廓微血管进行了变偏振光谱测量实验,实验证明了控制偏振态可以实现对血管不同深度的探测,为微血管断层光谱成像提供了一种新的研究手段。     

一种用于光纤链路振动信号模式识别的规整化复合特征提取方法

相位光时域反射链路监测系统是一种利用光纤作为传感介质的传感系统, 能够监测、定位、识别入侵信号.模式识别模块是其重要组成部分, 实时智能区分安全扰动和危险入侵.本文提出一种用于光纤链路振动信号模式识别的复合特征提取方法.利用改进的双门限方法确定有效信号段的起止位置, 结合最大能量与最高信噪比挑选出采样周期内主要入侵扰动的特征段.综合利用特征段时域持续时间和小波包能量谱提取复合特征向量, 使用支持向量机进行模式识别.实验表明, 基于本文提出的规整化特征提取方法的模式识别准确率有了显著提高.     

Quantitative assessment of effects of phase aberration and noise on high-frame-rate imaging

The goal of this paper is to quantitatively study effects of phase aberration and noise on high-frame-rate (HFR) imaging using a set of traditional and new parameters. These parameters include the traditional −6-dB lateral resolution, and new parameters called the energy ratio (ER) and the sidelobe ratio (SR). ER is the ratio between the total energy of sidelobe and the total energy of mainlobe of a point spread function (PSF) of an imaging system. SR is the ratio between the peak value of the sidelobe and the peak value of the mainlobe of the PSF. In the paper, both simulation and experiment are conducted for a quantitative assessment and comparison of the effects of phase aberration and noise on the HFR and the conventional delay-and-sum (D&S) imaging methods with the set of parameters. In the HFR imaging method, steered plane waves (SPWs) and limited-diffraction beams (LDBs) are used in transmission, and received signals are processed with the Fast Fourier Transform to reconstruct images. In the D&S imaging method, beams focused at a fixed depth are used in transmission and dynamically focused beams are used in reception for image reconstruction.The simulation results show that the average differences between the −6-dB lateral beam widths of the HFR imaging and the D&S imaging methods are −0.1337 mm for SPW and −0.1481 mm for LDB, which means that the HFR imaging method has a higher lateral image resolution than the D&S imaging method since the values are negative. In experiments, the average differences are also negative, i.e., −0.2804 mm for SPW and −0.3365 mm for LDB. The results for the changes of ER and SR between the HFR and the D&S imaging methods have negative values, too. After introducing phase aberration and noise, both simulations and experiments show that the HFR imaging method has also less change in the −6-dB lateral resolution, ER, and SR as compared to the conventional D&S imaging method. This means that the HFR imaging method is less sensitive to the phase aberration and noise.Based on the study of the new parameters on the HFR and the D&S imaging methods, it is expected that the new parameters can also be applied to assess quality of other imaging methods.     

One-dimensional and quasi-one-dimensional ZnO nanostructures prepared by spray-pyrolysis-assisted thermal evaporation

One-dimensional (1D) and quasi-1D ZnO nanostructures have been fabricated by a kind of new spray-pyrolysis-assisted thermal evaporation method. Pure ZnO powder serves as an evaporation source. Thus-obtained products have been characterized by X-ray diffraction (XRD) analysis, scanning electron microscope (SEM) equipped with energy dispersive X-ray spectroscopy (EDS), transmission electron microscope (TEM). The room temperature photoluminescence spectrum of these ZnO nanostructures is presented. The results show that as-grown ZnO nanomaterials have a hexagonal wurtzite crystalline structure. Besides nanosaws, nanobelts and nanowires, complex ZnO nanotrees have also been observed in synthesized products. The study provides a new simple route to construct 1D and quasi-1D ZnO nanomaterials, which can probably be extended to fabricate other oxide nanomaterials with high melting point and doped oxide nanomaterials.     

基于人的视觉特征的双正交小波基的构造

构造了一个与人的视觉系统模型的调制转移函数相近似的紧支撑双正交小波基。文中采用遗传算法，寻找一个紧支撑双正交小波函数，使它与调制转移函数在频域中相近似。同时将所构造的双正交小波基用于图像压缩，并将它与其它双正交小波进行比较。实验结果表明，所构造的紧支撑双正交小波基与Daubechies的9／3小波相比较有更高的压缩比，与9／7小波相比压缩性能相当，但计算量更小，它更适合于纹理图像的压缩。     

一种新的时间分辨光谱测量方法

提出用汇编语言编制程序控制单片机(AT89C51)及外围电路组成的驱动电路驱动步进电机带动单色仪旋转,得到各个期望波长的光,然后使光信号经过光电倍增管(Hamamatsu 1P28)进行光电转换后得到电信号,把电信号传进数字示波器,通过数字示波器上带有的RS232串口把光谱数据传回计算机处理得到各个波长光的衰减曲线、然后用计算机编程绘图进行处理得到时间分辨光谱的方法。这种测量时间分辨光谱方法的特点是测量各个波长光谱时,在时间上是并行测量而在波长上是串行测量的。通过测量样品Tb(o-BBA)3phen中稀土元素Tb发光的时间分辨光谱验证了这种方法的可行性。介绍了所用测试系统的各部分硬件组成和测试技术,获得了样品Tb(o-BBA)3phen的荧光强度-波长-时间的三维立体图以及对时间积分的积分谱。     

基于CCD电极直接驱动控制的双脉冲发光图像高速曝光技术原理研究

电荷耦合器件(CCD)是一类高性能的光电成像器件,具有成像阵列大、图像质量好的特点。但由于正常工作驱动时序复杂,工作帧频一般较低,无法满足较高成像帧频的要求。针对一种双脉冲发光图像的高速高分辨高质量成像要求,根据CCD信号电荷收集及转移的电极驱动特性,选择合适的CCD类型,以电荷转移时序为时间分隔界限,设计了一种电极直接进行控制的时序,实现了两个光脉冲图像的分离积分及信号转移、读出等,完成了双脉冲发光图像的等效高帧频曝光的原理验证,在保持CCD原有高成像质量的情况下获得了μs级间隔的两幅图像可分辨的能力,并实现了一种二分幅相机系统。