基于超窄脉宽激光器的厘米级测距技术研究

首先对影响脉冲激光测距精度的因素进行了分析,认为提高时间间隔测量计数器频率,采用快速电路,缩短激光脉冲上升沿时间和提高系统信噪比都可以提高脉冲激光测距精度,而缩短激光脉冲上升沿时间对提高测距精度效果明显。在此基础上,基于1.2 ns超窄脉宽激光器,设计了一种高精度脉冲激光测距实验装置,实验结果表明,单点测量精度小于1.2 cm。     

脉冲激光高精度测距的数据处理方法研究

采用电子计数法实现脉冲激光测距的本质是测量发射脉冲和目标反射回波脉冲的时间差.为实现脉冲激光精确测距,在分析传统电子计数法时间测量的原理和误差因素基础上,给出提高脉冲激光测距精度的几种数据处理方法,并分别论证了其有效性.     

脉冲激光测距中时间间隔的新的测量方法

脉冲激光测距在军事工业领域应用广泛,具有平均功率低、重复频率高和对光源相干性要求低等优点.通过提高脉冲激光测距中时间间隔的测量精度,可直接提高脉冲激光测距的精度.为了达到ps级测量精度,我们用单片机对时间测量芯片进行了控制,从而使其不但能对发射脉冲信号和返回脉冲信号延迟进行测量,而且还能对测量结果进行自动校准.与脉冲激光测距技术中用于测量时间间隔的传统方法相对比,这种方法简化了器件设计,提高了测量速度.     

激光脉冲弱小回波信号提取方法研究

在激光红外复合制导中,主动激光雷达可以提供探测目标的距离信息,并与红外探测方式实现光电互补,有助于提高复杂战场环境下精确制导的准确率。激光测距时,准确的回波位置检测是确保测距精度的关键。而信噪化是决定精度和作用距离的关键。为了提升脉冲回波信号的信噪比,本文提出了一种结合自相关滤波算法与改进的奇异值分解方法的微弱脉冲提取方法,并分别采用仿真数据和实际采集的脉冲激光回波信号进行去噪实验,实验结果表明,本文所提出的方法能够有效地提升回波信号的信噪比,有助于提高激光测距的精度。     

基于CPLD和单片机的激光测距时间间隔测量

为了达到提高时间间隔测量精度的目的,采用复杂可编程逻辑器件和单片机实现脉冲激光测距时间间隔测量系统中的模拟内插法的方案,设计了测量系统与测试电路,并对该方案进行了验证,得到了200ps精度的时间间隔测量系统.结果表明,可编程逻辑器件的使用可大大简化电路结构,使得整个系统结构简单化.采用该设计方案的激光测距系统具有体积小、可靠性高的特点.     

一种LD激光测距回波探测电路的设计

雪崩光电二极管APD(avalanche photo detector)因其具有很高的内部增益,是目前LD(Laser diode)激光测距中最常用的光电探测器件.挖掘激光测距系统的探测能力、提高探测概率的最终途径是提高激光回波信号的信噪比.从LD激光测距的特点出发,在分析了APD光电探测电路噪声的基础上,结合脉冲回波信号的特征,利用微弱信号检测的理论,提出了一种利用相关检测来提高回波信号信噪比的检测电路.结果表明,回波信号的信噪比有了一定提高,且结合了自动增益控制电路,为后续的时间间隔测量的精度提供了保证.     

一种提高脉冲激光测距精度的方法

在介绍脉冲激光测距原理的基础上,分析了影响脉冲激光测距精度的两种主要原因,脉冲时刻鉴别误差和时间间隔测量误差对测距精度的影响.指出了针对这两种原因的解决措施,介绍了采用高通容阻时刻鉴别法和差分延迟线法时间测量等技术,实现较高的测距精度的方法,对其工作原理作了介绍.     

基于TDC-GP22的脉冲激光测距系统设计

为满足激光测距领域大量程、高精度、高分辨率的应用需求,设计了一种高精度脉冲激光测距系统。系统基于最小可分辨45ps的专用计时芯片TDC-GP22实现高精度、高分辨率的时间间隔测量,并采用高带宽放大电路及恒比定时时刻鉴别方法提高系统精度。详细论述了TDC-GP22时间间隔测量模块的硬件设计及软件流程。实验结果表明,该系统的测量分辨率达45ps,对时间间隔1μs内的测量精度可达60ps,对应150m测距精度可达1cm;对时间间隔1μs以上的测量精度可达1ns,对应千米级测距精度可达0.15m,满足高精度距离测量的应用需求。     

基于回波信号插值重建的峰值判别技术

在脉冲式激光测距技术中,测量距离和目标反射特性变化等因素会引起微弱回波信号的峰值判别误差,造成激光飞行时间的测量误差,峰值判别误差是影响激光测距精度的主要因素之一.针对激光测距中微弱回波信号不规则引起的峰值判断精度低的难题,采用FPGA控制采样电路对回波信号进行高频采样,通过软件对采样数据进行插值重建,根据重建图形判断出回波信号的峰值点位置作为计数停止点,有效提高了回波信号峰值判别精度.实验证明:采用该项技术的激光测距机能够达到0.1 m测距精度.     

基于TDC7201芯片的高精度激光脉冲飞行时间测量模块研究

设计了一种高精度、高线性度、轻小型激光脉冲飞行时间测量模块。结合TDC7201芯片在时间测量方面的优势,将其作为时间测量核心部分,并将STM32F103RET6微控制器作为主控芯片来控制整个模块的工作。实验结果表明,该模块在12 ns~100 μs时间间隔范围内的时间测量精度最高可达4.1 ps;测量结果的线性拟合相关系数为1,且能够测量激光脉冲主波与5个回波之间的时间间隔。该模块可满足基于硅光电倍增管(Silicon Photomultiplier, SiPM)的脉冲式激光测距系统的高精度、高线性度、多回波、轻量化等实际应用需求。     

Resolution Enhancement Technology:Integrated Process Solutions using OPC

DUV lithography, using the 248 nm wavelength, is a viable manufacturing option for devices with features at 130 nm and less. Given the low kl value of the lithography, integrated process development is a necessary method for achieving acceptable process latitude. The application of assist features for rule based OPC requires the simultaneous optimization of the mask, illumination optics and the resist.Described in this paper are the details involved in optimizing each of these aspects for line and space imaging.A reference pitch is first chosen to determine how the optics will be set. The ideal sigma setting is determined by a simple geometrically derived expression. The inner and outer machine settings are determined, in turn,with the simulation of a figure of merit. The maximum value of the response surface of this FOM occurs at the optimal sigma settings. Experimental confirmation of this is shown in the paper.Assist features are used to modify the aerial image of the more isolated images on the mask. The effect that the diffraction of the scattering bars (SBs) has on the image intensity distribution is explained. Rules for determining the size and placement of SBs are also given.Resist is optimized for use with off-axis illumination and assist features. A general explanation of the material' s effect is discussed along with the affect on the through-pitch bias. The paper culminates with the showing of the lithographic results from the fully optimized system.     

Development of the readout system for waveguide multilayer optical card

Waveguide multilayer optical card （WMOC） is a novel storage device of three-dimensional optical information. An advanced readout system fitting for the WMOC is introduced in this paper. The hardware mainly consists of the light source for reading, WMOC, motorized stages addressing unit, microscope imaging unit, CCD detecting unit and PC controlling ＆ processing unit. The movement of the precision motorized stage is controlled by the computer through Visual Basic （VB） language in software. A control panel is also designed to get the layer address and the page address through which the position of the motorized stages can be changed. The WMOC readout system is easy to manage and the readout result is directly displayed on computer monitor.     

Cost-effective test solutions for smart card and other integrated flash applications

From its emergence in the late 1980s as a lower cost alternative to early EEPROM technologies, flash memory has evolved to higher densities and speedsand rapidly growing acceptance in mobile applications.In the process, flash memory devices have placed increased test requirements on manufacturers. Today, as flash device test grows in importance in China, manufacturers face growing pressure for reduced cost-oftest, increased throughput and greater return on investment for test equipment. At the same time, the move to integrated flash packages for contactless smart card applications adds a significant further challenge to manufacturers seeking rapid, low-cost test.     

An improved parallel thinning algorithm with two subiterations

The parallel thinning algorithm with two subiterations is improved in this paper. By analyzing the notions of connected components and passes, a conclusion is drawn that the number of passes and the number of eight-connected components are equal. Then the expression of the number of eight-connected components is obtained which replaces the old one in the algorithm. And a reserving condition is proposed by experiments, which alleviates the excess deletion where a diagonal line and a beeline intersect. The experimental results demonstrate that the thinned curve is almost located in the middle of the original curve connectivelv with single pixel width and the processing speed is high.     

Theoretical analysis of the relationship between the Brillouin gain coefficient and the strain in the optical-fiber sensors

The relation between the power of the Brillouin signal and the strain is one of the bases of the distributed fiber sensors of temperature and strain. The coefficient of the Bfillouin gain can be changed by the temperature and the strain that will affect the power of the Brillouin scattering. The relation between the change of the Brillouin gain coefficient and the strain is thought to be linear by many researchers. However, it is not always linear based on the theoretical analysis and numerical simulation. Therefore, errors will be caused if the relation between the change of the Brillouin gain coefficient and the strain is regarded as to be linear approximately for measuring the temperature and the strain. For this reason, the influence of the parameters on the Brillouin gain coefficient is proposed through theoretical analysis and numerical simulation.     

Novel fiber-optical interferometer with miniaturized probe for in-hole measurements

Today, micro-system technology and the development of new MEMS （Micro-Electro-Mechanical Systems） are emerging rapidly. In order for this development to become a success in the long run, measurement systems have to ensure product quality. Most often, MEMS have to be tested by means of functionality or destructive tests. One reason for this is that there are no suitable systems or sensing probes available which can be used for the measurement of quasi inaccessible features like small holes or cavities. We present a measurement system that could be used for these kinds of measurements. The system combines a fiber optical, miniaturized sensing probe with low-coherence interferometry, so that absolute distance measurements with nanometer accuracy are possible.     

Study of waveguide coupling efficiency in hybrid silicon lasers

This paper presents a new method to increase the waveguide coupling efficiency in hybrid silicon lasers. We find that the propagation constant of the InGaAsP emitting layer can be equal to that of the Si resonant layer through improving the design size of the InP waveguide. The coupling power achieves 42% of the total power in the hybrid lasers when the thickness of the bonding layer is 100 nm. Our result is very close to 50% of the total power reported by Intel when the thickness of the thin bonding layer is less than 5 nm. Therefore, our invariable coupling power technique is simpler than Intel＇s.     

A method for calculating the center position of collimated light

It is a key problem to accurately calculate beam spots＇ center of measuring the warp by using a collimated laser. A new method, named double geometrical center method （DGCM）, is put forward for the first time. In this method, a plane wave perpendicularly irradiates an aperture stop, and a charge couple device （CCD） is employed to receive the diffraction-beam spots, then the geometrical centers of the fast and the second diffraction-beam spots are calculated respectively, and their mean value is regarded as the center of datum beam. In face of such adverse instances as laser intension distributing defectively, part of the image being saturated, this method can still work well. What＇s more, this method can detect whether an unacceptable error exits in the courses of image receiving, processing and calculating. The experimental results indicate the precision of this method is high.     

Collinear phase-matching study of terahertz-wave generation via difference frequency mixed in GaAs and Inp

The collinearly phase-matching condition of terahertz-wave generation via difference frequency mixed in GaAs and InP is theoretically studied. In collinear phase-matching, the optimum phase-matching wave hands of these two crystals are calculated. The optimum phase-matching wave bands in GaAs and lnP are 0.95-1.38μm and 0.7-0.96μm respectively. The influence of the wavelength choice of the pump wave on the coherent length in THz-wave tuning is also discussed. The influence of the temperature alteration on the phase-matching and the temperature tuning properties in GaAs crystal are calculated and analyzed. It can serve for the following experiments as a theoretical evidence and a reference as well.     

Effects of the alloy compositions on the phonon-polaritons in ternary mixed crystals

Composition dependence of bulk and surface phonon-polaritons in ternary mixed crystals are studied in the framework of the modified random-element-isodisplacement model and the Bom-Huang approximation. The numerical results for Several Ⅱ - Ⅵ and Ⅲ- Ⅴ compound systems are performed, and the polariton frequencies as functions of the compositions for ternary mixed crystals AlxGa1-xAs, GaPxAS1-x, ZnSxSe1-x, GaAsxSb1-x, GaxIn1-xP, and ZnxCd1-xS as examples are given and discussed. The results show that the dependence of the energies of two branches of bulk phonon-polaritons which have phonon-like characteristics, and surface phonon-polaritons on the compositions of ternary mixed crystals are nonlinear and different from those of the corresponding binary systems.