短脉冲激光的二阶自相关

为了实现短脉冲激光的高动态范围信噪比(SNR)测量,满足快点火对激光驱动器的要求,开展了信噪比测量的前期研究.结合非线性晶体分析了超短脉冲的二阶自相关信号的产生过程,结果表明自相关曲线的信噪比等于原始脉冲的信噪比.同时讨论了非共线二阶自相关中,两束输入信号光的夹角变化对输出信号光强的影响.在此基础上,建立了一台二阶自相关仪以验证超短脉冲信噪比测量系统的工作性能,其信噪比测量的动态范围达到了约108.     

A Programmable SIMD Vision Chip for Real-Time Vision Applications

A programmable vision chip for real-time vision applications is presented. The chip architecture is a combination of a SIMD processing element array and row-parallel processors, which can perform pixel-parallel and row-parallel operations at high speed. It implements the mathematical morphology method to carry out low-level and mid-level image processing and sends out image features for high-level image processing without I/O bottleneck. The chip can perform many algorithms through software control. The simulated maximum frequency of the vision chip is 300 MHz with 16 times 16 pixels resolution. It achieves the rate of 1000 frames per second in real-time vision. A prototype chip with a 16 times 16 PE array is fabricated by the 0.18 standard CMOS process. It has a pixel size of 30 mum times 40 mum and 8.72 mum W power consumption with a 1.8 V power supply. Experiments including the mathematical morphology method and target tracking application demonstrated that the chip is fully functional and can be applied in real-time vision applications.     

倒装焊机视觉定位系统

倒装焊技术被越来越多地应用于微波组件和光电子器件等高频和高速电子产品的生产制造中。介绍了倒装焊机的功能要求。重点分析了复合精密定位平台和双面双视场光学系统的设计原理和系统设计方案。通过建立设计模型,提出一种实用的图像对位算法,经应用验证,该算法能满足系统的对位精度要求。     

自动排片机视觉系统的应用研究

介绍了自动排片机结构及其功能,着重分析研究了自动排片机的视觉系统,针对现有设备上使用的基于灰度识别算法的不足,比对了在Harris角点检测和SIFT算法的基础上,提出了一种适用于自动排片机图像识别算法。     

Higher Order Modes in RTHOCT

ＨｉｇｈｅｒＯｒｄｅｒＭｏｄｅｓｉｎＲＴＨＯＣＴＬｉｕＹｕａｎａｎ；ＴａｎｇＢｉｈｕａＡＮＤＧａｏＹｏｕｇａｎｇ（ＤｅｐａｒｔｍｅｎｔｏｆＴｅｌｅｃｏｍｍｕｎｉｃａｔｉｏｎｓＥｎｇｉｎｅｅｒｉｎｇ，ＢｅｉｊｉｎｇＵｎｉｖｅｒｓｉｔｙｏｆＰｏｓｔｓａｎ...     

Higher Order Cochlea-Like Channelizing Filters

A design method is presented for contiguous-channel multiplexing filters with many channels covering a wide bandwidth. The circuit topology extends previous work on cochlea-like channelizers by introducing multiple resonator-channel filter sections. The new design provides increased stopband rejection, lower insertion loss, and improved passband shape compared with the earlier version while retaining a simple design method and a compact layout, and requires no post-fabrication tuning. Results of a three-pole ten-channel channelizer covering from 182 MHz to 1.13 GHz with 17.5% bandwidth channels and 1.1-dB insertion loss are presented, and agree well with theory. A discussion of the power handling of planar channelizers is also presented.      

晶片焊线机视觉检测算法研究

全自动晶片焊线机是晶片生产的关键设备之一,其视觉检测系统是设备的核心技术所在.视觉检测技术直接影响晶片检测定位精度和焊接机的工作效率.分析了晶片检测原理和方法,研究了基于图像处理技术的晶片检测和定位算法,着重讨论了灰度模板匹配和二值模板匹配的方法.实验表明,系统在速度和精度上都可满足焊线生产的需求.     

一种应用于芯片高精度拾放的视觉定位方法

视觉定位技术是全自动芯片拾放设备的核心技术之一,其设计需结合设备功能、结构特点、运动方式来完成。介绍的视觉定位方法采用仰视与俯视双相机、俯视相机双镜头切换方式,适用于全自动粘片机、点胶机、晶圆芯片拾取机等设备中的拾放定位功能,及设备执行部件相对位置校验功能。     

基于高阶累积量的探地雷达信号处理

本文将高阶累积量方法应用于探地雷达浅层反射信号的处理。由于高阶累积量方法可用于非最小相位的系统辨识,并能抑制加性噪声的影响,故本文基于观测数据的三阶累积量进行探地雷达子波估计,并根据估计的子波进行逆滤波,改善信号的时频分辨率。在此基础上本文提出一种迭代方法,改善子波估计结果,据此得出的逆滤波结果有更好的时间分辨率和信杂比。     

A Low Power Analog CMOS Vision Chip for Edge Detection Using Electronic Switches

An analog CMOS vision chip for edge detection with power consumption below 20 mW was designed by adopting electronic switches. An electronic switch separates the edge detection circuit into two parts: one is a logarithmic compression photocircuit, and the other is a signal processing circuit for edge detection. The electronic switch controls the connection between the two circuits. When the electronic switch is off, it can intercept the current flow through the signal processing circuit and restrict the magnitude of the current flow below several hundred nA. The estimated power consumption of the chip, with 128 × 128 pixels, was below 20 mW. The vision chip was designed using 0.25 µm 1‐poly 5‐metal standard full custom CMOS process technology.     

Higher Order SVD Analysis for Dynamic Texture Synthesis

Videos representing flames, water, smoke, etc., are often defined as dynamic textures: "textures" because they are characterized by the redundant repetition of a pattern and "dynamic" because this repetition is also in time and not only in space. Dynamic textures have been modeled as linear dynamic systems by unfolding the video frames into column vectors and describing their trajectory as time evolves. After the projection of the vectors onto a lower dimensional space by a singular value decomposition (SVD), the trajectory is modeled using system identification techniques. Synthesis is obtained by driving the system with random noise. In this paper, we show that the standard SVD can be replaced by a higher order SVD (HOSVD), originally known as Tucker decomposition. HOSVD decomposes the dynamic texture as a multidimensional signal (tensor) without unfolding the video frames on column vectors. This is a more natural and flexible decomposition, since it permits us to perform dimension reduction in the spatial, temporal, and chromatic domain, while standard SVD allows for temporal reduction only. We show that for a comparable synthesis quality, the HOSVD approach requires, on average, five times less parameters than the standard SVD approach. The analysis part is more expensive, but the synthesis has the same cost as existing algorithms. Our technique is, thus, well suited to dynamic texture synthesis on devices limited by memory and computational power, such as PDAs or mobile phones.     

Higher Order Multipole Model of a Thin-Wire Helix

We investigate the field scattered from thin-wire helices by means of vector spherical harmonics rendering the fields of generated multipoles of arbitrary order. The excitation is varied in order to yield the characteristic T-matrix of a single helix column by column. The convergence with respect to the number and kind of required multipoles is checked by means of a simple test case. Further, we consider the mutual interaction of two helices. It is shown to be equivalent to an averaging process in terms of the number of required multipoles, which is thus limited. The helix model is then utilized to investigate reflection and transmission properties of a specific periodic arrangement which allows a comparison to a finite element based commercial software tool.     

高阶累积量在谱估计中的应用

本文提出了两种利用高阶累积量估计MA参数的新算法。当信号可以看作一个非高斯白噪声通过一个线性时不变系统的输出时,新算法运算简单、估计准确。本文还通过模拟实验分析了两种算法的性能。     

Robust Temporal Activity Templates Using Higher Order Statistics

A robust, theoretically founded approach for the extraction of temporal templates corresponding to areas of motion in video, is presented. Higher order statistics (kurtosis) are employed to extract activity areas, i.e., binary masks indicating which pixels in a video are active. The application of the kurtosis on illumination changes modeled as Gaussians and mixture of Gaussians is shown to be sensitive to outliers for both models, thus correctly localizing active pixels. Activity areas are compared to existing, difference-based temporal templates, known as motion energy images, and the robustness of both categories of temporal templates to additive noise is analyzed theoretically. Experiments with numerous real videos with additive noise, both indoors and outdoors, are conducted to compare the robustness of the activity areas and motion energy images, and their temporal extensions, the activity history areas, and motion history images. As expected from the theoretical analysis, the kurtosis-based activity areas prove to be more robust than the difference-based templates. Challenging videos containing occlusions, varying backgrounds, and shadows are also examined, and it is shown that the proposed approach outperforms the difference-based method for these cases, as well, consistently providing reliable localization of activity under a wide range of difficult circumstances. The proposed approach provides good results at a very low computational cost, and without requiring prior knowledge about the scene, nor training of any kind.      

Excitation of Higher Order Modes in Spherical Cavities

An analysis for determining approximately the optimum position of the exciting source inside a spherical cavity for exciting any TE or TM mode is presented. For any TE or TM mode the orientation of the exciting probe or loop is determined by maximizing the surface integral of /bar H/ or line integral of /bar A/ which is proportional to the excitation coefficient for the corresponding mode. Specific examples of mode discrimination by proper orientation of the exciting source are also included in the paper. Besides, graphs of the surface integral of /bar H/ and the line integral of /bar A/ for various modes are presented to indicate the variation of mutual inductance for any mode, for different positions of the exciting source.     

飞秒激光脉冲二阶干涉自相关法测量及其精细结构研究

本文用二阶相干自相关法测量飞秒激光脉冲宽度，测量过程完全由计算机控制和完成，测量精度达０．３飞秒。并分析了测量曲线的精细结构，发现其精细结构主要是由基频光相干场的振动频率所决定。     

倒装焊机中视觉系统的应用及对位算法研究

倒装焊是一种采用芯片与基板直接安装的互连工艺方法,使封装具有更优越的高频、低延迟、低串扰的电路特性。通过视觉系统优化及对位算法,极大地提高了生产效率和对位精度。     

倒装热压键合设备中热气流对视觉定位系统影响研究

利用加热装置对晶片样片进行加热,采用机器视觉定位系统对晶片进行拍照采样,并利用图像处理软件进行位置识别,分析了在加热对图像定位系统的影响,并采取了措施降低热气流的影响,取得了比较满意的结果.     

一种基于平衡式对数域积分器的高阶滤波器

提出了一个新的工作在甲乙类状态的平衡式对数域积分器 ,用跨导线性原理分析得到其传递函数。基于该积分器电路 ,采用无源网络模拟法设计出一个 1 d B波纹的五阶切比雪夫对数域低通滤波器。PSpice仿真结果表明 ,这种新型对数域滤波器能在低电压条件下工作 ,并具有高频、宽调谐范围和低失真等特点。     

On the Higher Order Modes of Elliptical Optical Fibers

The point-matching numerical method is here employed for the modal analysis of the elliptical optical fiber of any eccentricity. Good agreement with other analytical and numerical methods is obtained. Previous disagreement in the literature is resolved.