基于背向拉曼散射的分布工光纤温度传感器APD最佳雪崩增益的分析

本文分析了基于背向拉曼散射的分布式光纤温度传感器中光电接收用雪崩光电二极管雪崩增益对接收电路信噪比的影响，给出了使传感器系统接收电路输出信号噪比最大这一最佳意义下ＡＰＤ雪崩增益的表达式并进行了分析，实验结果和理论分析基本一致。     

提升激光探测灵敏度的设计方法

从光电接收电路信噪比与光电接收灵敏度的关系出发,研究了在不改变光电接受电路信噪比的前提下,提高光电接收电路探测微弱激光信号的能力。首先分析了提升光电接收电路灵敏度的两个方向,然后通过对比不同的探测器和放大器的技术参数,并经过电路仿真分析,确定了提升光电接收灵敏度的改进设计方案。最终经过实物电路的测试试验,证明采用新型的探测器和放大器能有效提高电路的信噪比和灵敏度,并可推广至其它相似的激光探测设备应用中。     

一种双色激光接收放大电路设计

为了实现对双色激光探测器的光电信号转换和处理,设计一种高增益光学接收电路.采用前置放大器和主放大器两部分放大电路,使用多级放大器级联,通过优化各级放大器的放大倍数和级间匹配,实现高增益放大,并转换为差分信号,实现与后级模数转换器件的匹配.通过对接收电路的测试表明,可以有效输出稳定的高增益高信噪比双色信号,实现前放100倍、主放56 dB的放大和差分信号输出.     

基于DSP的雪崩光电二极管数控偏压源设计

为保证雪崩光电二极管(APD)增益恒定,不受温度变化的影响而处于最佳工作状态,通过分析APD的增益和温漂特性,设计了一种APD偏压随温度按一定规律变化的数控偏压电路.采用DSP芯片TMS320F2812为主控制器,启动A/D转换对温度传感模块输出的电压信号进行采集,经计算处理得到APD的温度,然后由DSP输出相应的PWM信号来调节APD的偏压,从而保持APD增益恒定.该电路通用性好、可靠性高、操作性强,适合于高频连续信号检测的光电系统.     

闭环温度控制的APD光电探测器设计

针对微弱光信号探测系统中雪崩光电二极管(APD)在工作中的温漂特性,提出了一种适合APD的闭环温度控制方法.该方法将APD、热敏电阻器和TEC制冷器集成在同一组件中,采用模拟电路深度负反馈技术实现闭环温度控制,并运用经典的控制理论建立数学模型对PID电路进行优化,保证了APD探测电路的增益稳定性.试验表明:该系统中APD光电探测器温度控制精度为±0.1℃,输出电压波动约为±0.5 mV,很好地抑制了外界温度变化对APD增益的影响.     

基于盖革APD阵列的单通道激光雷达信号读出电路设计

随着测量技术的发展,激光雷达技术成为研究的热点,选取工作在盖革模式下的集成APD阵列雪崩二极管作为激光雷达的光电探测器,在探测距离为100-200m范围内,选择上升沿为5ns的激光脉冲,则接收带宽在70MHz~88MHz范围内,在此范围内APD探测器将接收到的回波信号转化为电信号,用TIA跨阻放大器反向放大模式将电流信号转化为电压信号,并将信号有效放大,输入至时刻鉴别电路,时刻鉴别电路用电压比较器来实现,最终可输出COMS逻辑电平信号;用TINA仿真软件进行仿真,仿真结果表明在接收带宽范围内TIA放大器的增益动态范围达到了54dB,总体电路延迟约为10ns。     

激光陀螺中雪崩光电管增益温度补偿

为保证激光陀螺中雪崩光电二极管(APD)在温度变化的情况下始终处于最佳工作状态,从APD的倍增机理出发,分析了温度对雪崩增益的影响,建立了虚警率与APD倍增因子的数学模型,并采用监测雪崩噪声平均过阈率的方法,得到器件的实际击穿电压温度系数γ=6.088×10-3/℃,按实测γ进行温度补偿,有利于提高APD增益的稳定性。     

应用于光散射技术中的光电探测器设计

针对光散射技术的应用,介绍了一种光电探测器的设计.给出了前置放大电路、滤波电路和主放大电路,分析了每一部分电路的工作原理,介绍了主要电学器件的特性.通过实验对电路响应的线性度和电路的信噪比进行了分析,并为提高电路的线性度和信噪比采取了相应措施.实验结果表明:该设计有输出信噪比高、可靠性强、探测精度高、光电转换稳定等优点,在光散射测量技术中有很好的应用前景.     

基于APD线列的单光子探测计数研究

单光子探测系统可以对单个光子进行探测;探测系统含有探测部分、淬灭电路部分和计数部分;探测部分主要由工作在盖革模式下的雪崩光电二极管组成;在盖革模式下的雪崩光电二极管发生雪崩后不能自然停止,淬灭部分主要为了主动抑制雪崩电流,快速降低雪崩电压,以达到提高探测效率,降低错误计数的目的;APD线列产生多个光子脉冲信号,计数部分的主要功能是对多路光子脉冲信号进行计数、显示并且可以控制每路APD的比较电压,保证每路APD淬灭电路的正常工作。     

基于ARM单片机的CO检测系统设计

针对目前气体检测系统灵敏度差、响应速度慢的问题,基于可调谐半导体激光吸收光谱技术,设计了一种带有参比气室的CO气体浓度差分检测系统.为了提高系统的灵敏度,系统综合运用了高增益雪崩光电探测器、差分吸收降噪和滤波降噪等方式提高了信号的信噪比.系统选用高速ARM单片机作为中央处理器进行数据分析处理和浓度反演,提高了检测速度.在软件中采用主成分回归分析建模,建立准确的分析模型.实验结果表明,该检测系统具有灵敏度高、性能稳定、抗干扰能力强等优点,有广淘的应用前景.     

Snow avalanche hazard modelling of large areas using shallow water numerical methods and GIS

Snow avalanches threaten settlements and roads in steep mountainous areas. Hazard mitigation strategies apply numerical models in combination with GIS-based methods to determine run out distances and pressure maps of snow avalanches in three-dimensional terrain. The snow avalanche modelling system is usually applied to study single avalanche tracks. In this paper we investigate the application of a numerical modelling system for large area hazard analysis. We begin by briefly presenting the depth-averaged equations governing avalanche flow. Then, we describe the statistical and GIS-based methods that are applied to define the initial fracture depths and release areas for snow avalanche modelling. We discuss the calibration of the avalanche model friction coefficients for extreme avalanches in function of altitude, avalanche size and topography. Seven test sites with areas between 100 and 350 km², that are well distributed over the different snow climates and elevation ranges of Switzerland, were used to calibrate the model by comparing the simulation results with historic avalanche events and existing avalanche hazard maps. We then show how the avalanche modelling system was applied over the mountainous region of Switzerland (25,000 km²) to delineate forests with protective function against avalanches.     

多输出布尔函数的k阶严格雪崩准则

首次将k阶严格雪崩准则的概念扩展到多输出布尔函数上,首先研究了多输出函数的严格雪崩准则、扩散准则,给出了多输出函数满足k阶严格雪崩准则的两个充分必要条件,证明了多输出布尔函数满足高阶严格雪崩准则时一定满足低阶严格雪崩准则。然后根据对称函数的特性,应用数论的知识,研究了多输出对称布尔函数的严格雪崩准则、扩散准则和k阶严格雪崩性质,给出了相应准则的充分必要条件,特别给出了两个k阶严格雪崩准则的组合判别公式。     

Flat panel detector based on a shadow mask plasma display panel

A flat panel detector based on the structure of a shadow mask plasma display panel is analyzed in terms of the electron amplification factor when used in the Townsend mode. The detector consists of a metal shadow mask and two ultra‐thin glass substrates with electrodes depositing on them. The shadow mask divides the detecting area into arrays of independent cells. The electron gain and linearity of the device are investigated by simulation based on the particle‐in‐cell/Monte Carlo collision model. Similar experiments are carried out. Both experimental and simulation results show that the linearity of the detector is significant. The applied voltages and the effective cathode area are parameters affecting its gain. As the avalanche process in the center of the cell with small electric field strength is much smaller than that near the shadow mask edge, the gain increases exponentially with the anode voltage but decreases with the negative shadow mask voltage. The balance between effective cathode area and high electric field intensity near the shadow mask edge provides room for future optimization of the detector. In conclusion, the flat panel detector is a promising component in a detection system for high energy radiation, and the wide application of the device is expected.     

High frequency scanning response of an APD photocurrent for laser range finder

In this paper, the scanning response of the photocurrent emitted by a large area avalanche photodiode (APD) is studied for a 3D laser camera. This 3D camera is based on a phase-shift laser range-finder to measure distance from 1 to 20 m. To obtain a large field of view of the optical head, a large area APD working as an optoelectronic mixer is used. Photocurrent response versus light spot position above the APD active area is analysed for high frequency measurements. Optoelectronic mixing permits to measure the scanning response phase of the internal photoelectric current. Moreover, it is demonstrated that the signal phase depends on the photoelectric gain. Signal-to-noise ratio and distance measurement error for the 3D camera are then discussed.     

Visual simulation of mixed-motion avalanches with interactions between snow layers

In the field of computer graphics, simulation of fluids, including avalanches, is an important research topic. In this paper, we propose a method to simulate a kind of avalanche, mixed-motion avalanche, which is usually large and travels down the slope fast, often resulting in impressive visual effects. The mixed-motion avalanche consists of snow smokes and liquefied snow which form an upper suspension layer and a lower dense-flow layer, respectively. The mixed-motion avalanche travels down the surface of the snow-covered mountain, which is called accumulated snow layer. We simulate a mixed-motion avalanche taking into account these three snow layers. We simulate the suspension layer using a grid-based approach, the dense-flow and accumulated snow layer using a particle-based approach. An important contribution of our method is an interaction model between these snow layers that enables us to obtain the characteristic motions of avalanches, such as the generation of the snow smoke from the head of the avalanche.     

一种PM2.5检测传感器设计

为了减小和防治灰霾天气对人们生活和健康的不利影响,对灰霾检测设备进行了研究,提出了一种PM 2.5检测传感器设计。根据光电传感器原理,采用对射型检测方式,将波长为650nm、功率为10mW的半导体激光器作为光源,使用具有内增益、灵敏度好的雪崩光电二极管作为接收器,经过由I/V转换、电压放大和具有低偏压差、低温度漂移、高性能电压跟随器构成的调理电路处理后,完成对颗粒物检测传感器设计。实验结果表明:该传感器测量准确、响应快、误差小,为准确测量颗粒物的浓度提供了硬件基础。     

Characterization of electronic displays using CMOS single‐photon avalanche diode image sensors

Advanced complementary metal‐oxide semiconductor‐compatible single‐photon avalanche diode array technology is progressing rapidly and is being deployed in a wide range of applications. We report for the first time the use of a complementary metal‐oxide semiconductor‐compatible single‐photon avalanche diode array to perform detailed optical measurements on pixels of an organic light‐emitting diode microdisplay at very high sampling rate, very low light level, and over a very wide dynamic range of luminance. This offers a clear demonstration of the huge potential of this single‐photon avalanche diode technology to reveal hitherto obscure details of the optical characteristics of individual and groups of organic light‐emitting diode pixels.