三轴光电跟踪系统的实时引导

三轴光电跟踪系统是地平式和X-Y式光电跟踪系统的有机组合,可以全方位跟踪空间运动目标,跟踪系统测量值与空间位置的多对一特性决定了跟踪策略的多样性和系统引导的复杂性,跟踪过程中对系统进行实时引导可以提高系统的跟踪精度及其可靠性。各种跟踪策略下三轴光电跟踪系统的引导过程包括:地平式的引导、X-Y式的引导、具视轴偏角的地平式引导、三轴光电跟踪系统的引导等。通过理论分析,给出了各种情况下的引导方法。     

光电跟踪测量系统的动态成像分辨率分析及优化设计

光电跟踪测量系统的测量精度与成像质量受成像系统动态分辨率的影响.成像系统动态分辨率受光电跟踪测量系统跟踪精度的影响.分析与试验表明,光电跟踪测量系统的动态成像分辨率主要取决于静态分辨率和跟踪精度;工作过程中的光电跟踪测量系统的动态成像分辨率比光电跟踪测量系统的静态成像分辨率低;与传感器的积分时间相比,高频目标与低频目标对动态成像分辨率的影响模型不同;在传感器积分时间、目标的运动状态及对动态分辨率要求确定的条件下,可对静态成像分辨与控制系统进行优化设计.     

基于球谐函数的三轴光电跟踪系统误差修正方法

三轴光电跟踪系统不存在空间跟踪盲区，为了提高系统引导或轨道测量精度，需要修正其系统误差。最小二乘系统误差修正方法精度较低，球谐函数系统误差修正有较高的修正精度，球谐函数系统误差修正方法应用到三轴光电跟踪系统中时存在困难。理论分析指出，应用球谐函数的系统误差修正需要在三轴光电跟踪系统中针对不同的方位建立多组修正参数。仿真表明，三轴光电跟踪系统中通过建立多组修正参数的球谐函数系统误差修正方法可以把系统误差降低到原来的30％。     

捷联稳定技术在两轴光电跟踪仪中的应用

载体平台摇摆对两轴光电跟踪仪光轴指向的扰动是制约光电跟踪仪跟踪稳定性和跟踪精度提高的关键因素.本文首先从控制原理出发比较了传统速率稳定方式与捷联稳定方式,然后针对两轴光电跟踪仪捷联稳定方式建立了扰动作用于光轴指向分量的数学模型,最后对某型光电跟踪仪采用了捷联稳定技术,并设计了相应的伺服系统,试验表明此系统设计合理,满足...     

三级管道流水线算法实现红外点目标跟踪

针对海空复杂背景下舰载光电跟踪仪的红外点目标检测跟踪问题,本文研究了一种基于三级流水管道的点目标轨迹检测与跟踪算法.该算法针对由光电跟踪仪实际拍摄的红外图像的二值分割图,利用第一、二级流水管道,完成对二值图像的二阶相关,实现更为有效的滤波除噪.利用第三级基于"或运算"的目标检测管道搜索目标点和进行目标点的准确定位,从而实现了从序列图像中可靠检测和跟踪点目标的目的.本文采用舰载光电跟踪仪实拍的红外图像,进行了实际的工程验证.结果说明,工程验证的结果与实验仿真结果相吻合,算法是可行的.     

低空慢速小目标探测与定位技术研究

城市大型集会、活动中安保工作的一大主要任务是防止恐怖分子利用航模等低空慢速小型飞行器进行破坏活动,由于城市环境的复杂性以及低空慢速小目标(以下简称"低慢小")的特殊性,像雷达等传统的探测方法很难准确探测定位。针对这一难题,设计基于激光探测技术的低慢小探测与定位系统。系统包含激光脉冲发射、雪崩光电二极管偏置、弱光信号处理和计时电路等主要结构。利用标准时基发生器对计时电路进行验证,采用线性拟合方法使时间测量的精度达到10-10量级。经过试验测试,该系统能够在近距离范围内对低慢小进行快速定位,0~100 m距离范围内测距误差为±0.6 m;0~60 m高度范围内测高误差为±0.6 m;0~35 km/h速度范围内测速误差为±1.3 km/h。     

2m比长仪纳米级精度线间距测量系统的研究

介绍了2 m比长仪系统的组成,对其采用光电显微镜动态瞄准刻线和激光干涉测长原理进行了分析,研究了提高刻线瞄准精度和激光干涉测长精度的方法及利用现代电子技术实现刻线信号和干涉信号自动同步快速处理方法。自动信号处理系统基于FPGA现场可编程电路技术和计算机技术。通过对金属线纹尺测量的实验表明,依据JJG 331—1994激光干涉比长仪检定规程进行实验,2 m比长仪单次最佳刻线瞄准精度优于10 nm(1σ),对其测量的不确定度分析表明,对于测量高质量的高等别线纹尺,其测量不确定度U=（20+40 L）nm（k=2）。     

无激光测距的动平台经纬仪单站精确测量

在空间较小的动平台上,光电经纬仪在目标进近下滑段离飞行目标距离很短(小于200 m),此时跟踪角速度大,很容易丢失激光合作目标,且会出现激光漫反射现象,导致激光测距信息无效。为解决无激光测距无法使用原有方法进行轨迹测量的问题,本文提出无激光测距的经纬仪单站精确测量方法,其在经纬仪精确标定的基础上,结合中线视频、经纬仪视频和平台运动姿态,采用空间几何和共线条件的方法实现目标单站定位测量。试验结果表明该方法具有标定简易、定位精度高、可靠性强等优点,动态条件下实际测量精度,飞行方向优于0.3 m,高程方向优于2.5 cm,由中线视频获得的偏航精度优于5 cm,满足测试需求。     

一种三轴光电跟踪系统指向误差修正的方法

为了提高三轴光电跟踪系统的指向精度,针对三轴光电跟踪系统的光机结构提出了一种具有明确物理意义的指向误差修正模型。首先,根据四元数的旋转变化方法详细分析了各轴系误差对空间目标指向误差的映射关系表达式,然后,通过这些关系式建立三轴光电跟踪系统的指向误差修正模型。实验结果表明,该方法可以将有效的修正系统指向误差,且外符合修正精度高于球谐函数指向误差修正模型,同时该方法在装配调试阶段对预估指向精度具有一定的参考指导作用。     

基于MEMS平面弹簧的微小载荷测试方法

本文提出一种微小载荷测量方法,搭建了基于MEMS平面弹簧的测量装置,主要由支撑臂、MEMS平面弹簧和激光位移探测器组成.通过激光位移探测器测量MEMS平面弹簧的微小变形,换算得到所施加的微小载荷.采用深反应离子刻蚀(DRIE)等微加工工艺制作了平面微弹簧,并对其进行理论计算和仿真模拟,给出了刚度范围,最后通过实际测量的方式进行了实验标定.结果显示:MEMS平面弹簧的标定刚度为7.88 mN/μm,其结果与理论及仿真结果较接近,测量精度可达0.08 mN.使用该装置和精密电子天平分别对10组微小质量试块进行测量,其平均误差率为5.75%.     

Optoelectronics in satellite designs

Design of artificial satellites for communication, remote sensing and scientific investigations follows, at present, a fixed pattern based on existing and proven technologies and the requirements of payload or experiment within the constraints of weight, volume and power available. The advances in optoelectronic components and systems have opened up a new dimension in designing satellites of the future, incorporating new technologies. This paper deals with general satellite design concepts based on optoelectronic systems wherever applicable.     

全极化微波辐射计遥感海面风场的 关键技术和科学问题

全极化微波辐射计是一种新型的微波遥感器,它不但测量目标微波辐射信号的两个正交极化分量,并且测量两个正交极化分量的复相关量。这些相关信息对于表面微波辐射的各向异性更加敏感,这样就提供了测量海面风场的一种手段。 文章在介绍国内外全极化微波辐射计现状和特点的基础上,首先对于全极化微波辐射计遥感海面风场的原理及其影响因素进行分析;然后,从全极化微波辐射计的硬件设计和定标两个方面论述了硬件实现的关键技术问题;最后,对于风场反演的有关科学问题进行分析,重点论述了风场反演算法建立的关键,主要技术指标对于风场反演误差的影     

海水盐度遥感反演精度的理论分析

利用海面微波辐射的理论模型和海水介电常数计算公式,对影响海水盐度遥感反演精度的有关因素进行了分析计算,包括波段的优选、极化方式和入射角的设计、温度和盐度对反演精度的影响。结果表明,降低亮温对温度的敏感性应该作为选择盐度遥感波段时考虑的一个重要条件,双极化、较大入射角的天线工作方式有助于提高盐度遥感的精度,但是在低温或低盐条件下仍难以达到较高的盐度反演精度。     

一种目标提取新方法-光谱排序编码法

为了进一步提高光学遥感目标提取精度,拓展目标提取方法的适用范围,推进遥感智能化信息提取方法的发展,本文从谱带强度与波形特征有机结合的角度出发提出了光谱排序编码法.首先介绍了该方法的基本原理:对端元光谱与图像光谱按谱带强度大小各自进行排序的基础上,通过比较同一顺序上的波段位置的异同来计算两条光谱曲线的相似度;然后开展了与约束能量最小法(CEM)、光谱二阶导数法(SSD)的目标提取精度对比实验,结果表明该方法的目标提取精度为95%,比CEM提高了41.9%,比SSD提高了46.9%;最后利用SPOT多光谱和AVIRIS高光谱数据检验了该方法在目标提取适用范围上的能力,结果表明该方法既适用于多光谱遥感,又适用于高光谱遥感.总之,算法具有速度快、精度高、适用范围广的特点.     

Piezoelectric-transducer-based optoelectronic frequency synchronizer for control of pulse delay in a femtosecond passively mode-locked Ti:sapphire laser

We propose a piezoelectric transducer-(PZT-) based optoelectronic frequency synchronizer to control simultaneously change in the repetition rate, the relative pulse delay, and the phase noise of a passively mode-locked femtosecond Ti:sapphire laser with an intracavity saturable Bragg reflector absorber with respect to an electronic frequency reference. An optoelectronic phase-locked-loop-based PZT feedback controller with a proportional, integral, and differential (PID) circuit and a tunable voltage regulator is designed to achieve frequency synchronization, phase-noise suppression, and delay-time tuning. When the controlling voltage is tuned from -2.6 to 2.6 V, the maximum pulse-delay range, tuning slope, and tuning resolution of the laser pulse-train are 11.3 ns, 2.3 ps/mV, and 1.2 ps, respectively. Setting the gain constant of the PID circuit at 10 or larger causes the delay-time tuning function to be linearly proportional to the controlling voltage. In the delay-time tuning mode the uncorrelated single-side-band phase-noise density of the frequency-synchronized laser is approximately -120 dBc/Hz at an offset frequency of 5 kHz, which is only 7 dBc/Hz higher than that of the electrical frequency reference. The proposed system also supports linear,continuous switching,and programmable control of the delay time of Ti:sapphire laser pulses when they are frequency synchronized to external reference clocks.     

Precision ranger for measuring large mechanical components

We present a precision laser ranger system for the measurement of large manufactured components and structures. The system was developed based on a beat-wave interferometry principle. The light source of this system is a frequency-stabilized laser with a frequency stability of 1 x 10(-7) (in open air) or 10(-8) (in the laboratory). The laser operates in two longitudinal modes, and the two modes are generated in common resonator; therefore the two beams are naturally coaxial. The precision ranger system does not need a long guide or any heavy machinery. In this system an adaptive filter and a wavelet-transform program are used to improve the measurement accuracy. The system described here has a measuring range of 0-20 m and a measuring uncertainty of 30 microm/10 m.     

Timing jitter reduction and single-frequency operation in an acousto-optic Q-switched Cr,Nd:YAG laser

A laser-diode-pumped watt-level single-frequency combined actively and passively Q-switched (CAPQ) laser with a wavelength of 1064 nm that simultaneously uses a codoped Cr(4+),Nd(3+):YAG crystal as the gain medium and mode selector is presented. The optimum repetition period of the CAPQ laser is approximately 1.5 times the natural repetition period of the passively Q-switched laser. The averaged timing jitter is approximately 400 ns in the CAPQ laser and the repetition rate of the CAPQ laser is experimentally shown to reach a time instability of 0.2% over 10(6) pulses. The output is a stable single frequency with a linewidth of 400 MHz at 20 W pump power.     

Experimental demonstration of multiple pulse nonlinear optoacoustic signal generation and control

Generating underwater acoustic signals from a remote, aerial location by use of a high-energy pulsed infrared laser has been demonstrated. The laser beam is directed from the air and focused onto the water surface, where the optical energy was converted into a propagating acoustic wave. Sound pressure levels of 185 dB re microPa (decibel re microPa) were consistently recorded under freshwater laboratory conditions at laser-pulse repetition rates of up to 1000 pulses/s. The nonlinear optoacoustic transmission concept is outlined, and the experimental results from investigation of the time-domain and frequency-domain characteristics of the generated underwater sound are provided. A high repetition rate, high-energy per pulse laser was used in this test under freshwater laboratory conditions. A means of deterministically controlling the spectrum of the underwater acoustic signal was investigated and demonstrated by varying the laser-pulse repetition rate.     

Development of optoelectronic-based pulsed current sensor to detect the poor laser discharge condition

A current transformer (CT)-based sensor has been developed to detect poor discharge conditions in copper vapour laser. The optoelectronic-based pulsed current sensor architecture involves the optical transmitter–receiver HFBR, high-frequency current transformer, and fiber optic link. The CT has been designed and calibrated to ensure generation of an optical signal at the current threshold crossover. Bandwidth analysis of the CT is carried out using the bode plot. The optoelectronic inter-conversion of the pulsed voltage of the CT and transmission via fiber optic link provides the non-contact current sensing and remote signal processing of the signal. This study discusses the details of the sensor.     

The "advanced disk laser" — An onboard laser diagnostics system for drop tower experiments

We report about recent developments concerning the "Advanced Disk Laser" system, which is intended for use in combustion experiments under microgravity conditions at the drop tower "Bremen". Since the system will be integrated into a modified drop capsule it has to be a compact and efficient solid state laser which can withstand decelerations of up to 40 g. The existing laboratory set up was redesigned to fit into the capsule. Therefore, the system layout was split in three platforms for optical components (seed laser, regenerative amplifier and frequency conversion) and one additional platform for media supplies. Afterwards, a special developed ultra stable structure was equipped with newly designed mechanical and electro-optical components, which in part have already been tested in drop experiments. Access for alignments is possible via remote control of a number of motorized mechanical mounts. The three optical platforms build a vibration-insulated, dust-free laser capsule of their own inside the drop capsule and can be used both in the capsule and in a laboratory environment. The new laser system was already optically adjusted and tested in the laboratory and reached a pulse energy of 20 mJ, as was expected. An extensive evaluation period is going to follow and will be finished with a series of combustion experiments.