变阈噪比优化机载IRST系统的探测概率包线

基于机载红外搜索跟踪(IRST)系统噪声源的特点,建立了一种探测概率模型,分析了探测过程中阈噪比对探测概率、虚警概率的影响。基于作战背景,分析了探测距离、目标速度、作战环境对探测概率的影响。在探测过程中动态设置阈噪比,给出了具体求解方法,并对不同任务需求下的阈噪比取值范围进行仿真分析。利用求解的阈噪比值,仿真得出了变阈噪比情形下的探测概率包线。研究结果表明,与恒定阈噪比方法相比,采用变阈噪比求得的概率包线能够适应实时变化的空战条件,普适性更强,探测距离明显增大。     

基于Gm-APD的成像激光雷达目标探测特性

针对采用盖革模式雪崩光电二极管（Gm-APD）作为探测器的成像激光雷达,介绍了其测距原理及3D成像原理,并对如何提高其探测性能的方法进行了分析。以分析Gm-APD触发信号的统计特性为基础,对出现在距离门内不同位置目标的探测概率和虚警概率进行了研究与仿真,结果表明,目标处在距离门最前面时,探测概率受噪声水平影响最小,虚警概率受信号强度影响最大;目标靠近距离门中间位置时,探测概率随噪声水平增大下降缓慢,虚警概率随信号强度增大下降缓慢;目标处在距离门末尾时探测概率受噪声水平影响最大,而虚警概率几乎与回波信号强度无关。     

光子成像系统信号与噪声的统计特性分析

在去除光子图像的本底噪声时,根据微弱点目标的探测统计特性,以泊松分布均值与方差相等的特点为判据,提出了一种确定阈值选取范围的新方法。利用点过程的分析方法研究了光子受限点目标的探测统计特性,并进行了实验研究,结果表明光子受限点目标的探测统计特性服从平稳泊松点过程。利用以上分析方法可以快速地获得微弱点目标事件的期望发生率,以及在下一段时间内目标至少再出现一次的概率,从而为后续的目标探测、跟踪以及位置预测奠定了基础。     

基于光流直方图的云背景下低帧频小目标探测方法

对低帧频、云层背景下,低信噪比的弱点目标探测率降低的问题.提出了光流直方图(OFH)的定义.并且给出了OFH的性质.分析了低帧频下红外图像探测弱点目标时探测率降低的原凶,提出了一种基于OFH背景补偿的红外点目标探测算法.利用OFH得到背景的运动欠量.进行运动背景补偿;然后利用目标与云层运动差异性,得到帧间比较结果,并对比较结果通过Robinson滤波器进一步滤除残留的边缘,达到降低虚警的目的.实验结果表明,该算法中以显著提高往复杂背景下红外点目标检测概率,并凡能够探测出信噪比为1的目标.     

光子成像静止点目标的管道滤波探测方法

构建了具有单光子成像能力的光子成像系统,提出应用管道滤波方法实现对光子受限静止点目标的探测。分析了光子图像静止点目标与点状噪声特征,根据静止点目标在序列图像中位置的确定性以及噪声点的不相关性,研究了基于管道滤波的光子成像静止点目标探测方法。为降低目标探测的虚警概率,优化了管道滤波直径。以实验采集得到的多组光子图像序列为样本,获得了探测概率、虚警概率与信号光子数、噪声光子数、管道长度以及检测阈值的关系。检测结果显示,对信号与噪声的平均发生率为0.4和5.215的序列图像,当管道长度为9、检测阈值为2时,探测概率达0.9以上且虚警概率〈0.08。对比多组图像序列的检测结果表明,影响探测概率的主要参数是信号光子数,而影响虚警概率的主要参数是噪声光子数。     

复杂环境下机载光电系统探测概率包线研究

针对机载光电系统理论与实际探测能力之间的较大差异及其作战能力发挥不充分等问题,分析得到了目标反射背景辐射的空间分布函数,并给出了具体量化方法,进而研究了目标本征辐射特性,建立了水平和俯仰面内的辐射强度包线模型;之后考虑各种作战因素,给出了机载光电系统角水平和角俯仰探测能力包线计算方程式;最后提出探测概率包线概念,得到了机载光电系统作用距离与探测概率关系,并定量分析了机载光电系统探测包线的概率特性。仿真结果表明,探测包线随目标速度、方位、俯仰的变化而实时变化;当满足一定的虚警概率和信噪比要求时,探测概率包线具有最佳探测点,这为充分发挥机载光电系统探测性能提供了理论参考。     

基于M&M′态的量子照明目标探测

在目标回波光子仍为纯态的假设前提下,推导了MM′态的量子照明目标探测错误概率边界,并与非纠缠Fock态、NOON态进行了对比.仿真结果表明:MM′态相对于非纠缠Fock态的探测优势仅受限于信号与闲置光路间光子数的分配比例;这使得以MM′态作为光源的量子照明探测,能够在更大信噪比动态范围内(至少两倍于NOON态)获得优于非纠缠Fock态的目标探测性能.     

基于粒子群算法的动态热释电目标跟踪

热释电传感器用于红外目标跟踪,可以通过光学调制探测到运动目标的相对方向,而不能确定其准确距离,对此提出一种群智能搜索的动态热释电跟踪方法。传感器在摆动状态下感知红外目标,发现目标时,记录其探测角,通过分析探测角序列与运动目标轨迹离散点在极坐标系下的关系,将目标轨迹的确定转化为极径序列的确定,然后建立关于极径序列的多维粒子群空间,并构造评价粒子优劣的适应度函数,实现了运动目标轨迹的跟踪。该方法扩大了热释电探测范围,提高了目标跟踪精度,通过人体目标直线、曲线运动跟踪实验得出平均定位误差不超过0.4m,表明方法有效。     

基于二阶振动系统响应模型的激光制导信号动态模拟

针对载机平台上的激光目标指示器照射过程的动态响应及其模拟,利用高斯白噪声,通过由滤波器产生的有色噪声的方法模拟了目标指示器指示激光光斑抖动信号的统计平均特征,分别进行了抖动光斑位置随时间变化和在简化地物模型下漫反射信号强度随时间变化的动态模拟以及实际验证测试。经分析表明:在载机平台上,激光动态照射过程中的反射信号强度的变化是与平台相对于目标运动、目标表面的漫射特性和反射特性等因素相关的综合函数;基于二阶振动系统响应模型的方法可应用于激光目标指示器照射过程中的激光制导信号的大气传输和探测的动态模拟。     

基于并行隔帧差分光流场与灰度分析综合算法的运动目标检测

提出了隔帧差分的概念,并将其应用于光流场算法中,用改造后的隔帧差分光流场算法成功克服了传统光流场算法的不足(传统光流场算法不能识别帧间位移小于一个像元的运动目标).进一步对光流场计算结果与原始图像进行灰度综合分析,使目标的探测更加准确,减少了虚警和误判.采用不同间隔的序列差分构成并行识别系统结构,使整个系统能够探测各种不同速度的运动目标.实验结果表明:提出的运动目标检测算法能够准确有效地检测出不同速度的运动目标.     

基于图像融合的动态轮廓线跟踪新方法

红外与可见光传感器是目标跟踪识别系统中常用的两种传感器,对这两种传感器图像进行融合能有效提高系统跟踪检测的准确性。将动态轮廓线模型与图像融合结合,在特征搜索过程中利用特征点准确地完成了图像配准,同时使用了一种新的特征级融合方法,将两种图像中目标轮廓的B样条曲线控制点进行实时微分耦合。这种耦合将Curwen提出的微分耦合机制作了改进,利用图像配准把刚性硬模板改变为实时的变换模板并推导了融合后动态轮廓线的新的动力学方程。这种融合利用了红外图像目标轮廓信息约束可见光图像中动态轮廓线的收敛形状,有效地提高了可见光图像目标跟踪的准确性。对运动人手序列图像的对比跟踪实验表明,这种融合使得可见光图像中动态轮廓线平均跟踪误差减小了60．25％。     

对各种红外系统的灵敏度方程的修正

当目标为灰体时,尤其是目标温度与环境物体的温度相近时,必须同时考虑目标的自身辐射和它对环境辐射的反射。这样,各种红外系统的灵敏度方程就需要修正。根据这些修正后的方程,就可以解释原来只考虑自身辐射的方程所无法解释的实验现象。其中,对于热成象系统,我们作了重点讨论,不但考虑了场景中相邻单元的温差、比辐射率差和反射率差的影响,而且考虑了扫描效率、扫描重迭率、串联或并联列阵元件、加场镜或浸没透镜等的影响,得到比较完整的灵敏度方程和噪声等效温差NETD的表达式。对于NETD中的积分X_T的计算方法,我们也作了介绍并给出数值表。 关键词：     

The bifurcation threshold value of the chaos detection system for a weak signal＊

Recently, it has become an important problem to confirm the bifurcation threshold value of a chaos detectionsystem for a weak signal in the fields of chaos detection. It is directly related to whether the results of chaos detectionare correct or not. In this paper, the discrimination system for the dynamic behaviour of a chaos detection system fora weak signal is established by using the theory of linear differential equation with periodic coefficients and computingthe Lyapunov exponents of the chaos detection system; and then, the movement state of the chaos detection system isdefined. The simulation experiments show that this method can exactly confirm the bifurcation threshold value of thechaos detection svstem.     

Quantum filtering for multiple input multiple output systems driven by arbitrary zero-mean jointly Gaussian input fields

In this paper, we treat the quantum filtering problem for multiple input multiple output (MIMO) Markovian open quantum systems coupled to multiple boson fields in an arbitrary zero-mean jointly Gaussian state, using the reference probability approach formulated by Bouten and van Handel as a quantum version of a well-known method of the same name from classical nonlinear filtering theory, and exploiting the generalized Araki-Woods representation of Gough. This includes Gaussian field states such as vacuum, squeezed vacuum, thermal, and squeezed thermal states as special cases. The contribution is a derivation of the general quantum filtering equation (or stochastic master equation as they are known in the quantum optics community) in the full MIMO setup for any zero-mean jointly Gaussian input field states, up to some mild rank assumptions on certain matrices relating to the measurement vector.     

基于光场一阶关联的时域成像

与通常利用二阶强度关联测量实现时域鬼成像不同,本文利用时域热光源借助干涉仪通过一阶关联实现时域成像.基于空域光束的近轴衍射和时域窄带脉冲在色散介质中色散之间的空间-时间二象性,在时域脉冲响应函数的基础上得到了表征一阶关联时域成像的强度表达式,分析研究了光源脉冲宽度和相干时间对成像可见度和分辨率的影响.结果一方面表明基于热光场一阶关联的时域成像在不需要额外色散补偿或消除条件下可以实现时域物体信号的再现,另一方面表明当光源脉冲宽度一定时,成像可见度随光源脉冲相干时间的增加而增加,但是成像分辨率逐渐降低,其中当光源脉冲宽度约为100 ps,相干时间约为0.5 ps时,间隔为20 ps,宽度为8 ps的时域矩形波型物体的成像质量(兼顾可见度和分辨率)较好.该结果对于基于热光一阶关联的时域成像在时序信号测量中的应用具有重要意义.     

一种基于图像融合的运动目标快速检测算法

提出了一种新的运动目标检测方法,这种方法可以有效的提取目标轮廓。应用一种图像差分技术得到运动目标的初始轮廓线。使用了动态轮廓线使其收敛到目标轮廓。提出了一种新的目标轮廓特征级融合方法,求解两类模式图像的收敛动态轮廓线控制点向量差的范数平方极小化。这种方法不需要图像配准降低了融合的计算复杂度,有效提高了可见光图像中目标轮廓提取的精度。对比检测实验证实了算法的有效性。设计了一种基于Newmark方法的动态轮廓线快速迭代算法,将该方法和方法作了比较,对比实验表明这种方法的时间复杂度降低了22%。     

Analytic-Numerical Construction of Nonstationary Probability Distributions for one Class of Nonlinear Stochastic Systems

We propose a method for constructing nonstationary model probability distributions for nonlinear dynamic systems related to the Verhulst stochastic equation. The proposed procedure is based on the numerical solution of relaxation differential equations for the mean and the variance. The set of the moment equations is closed and the probability density is constructed on the basis of rigorous analytical relations for the stationary probability characteristics. As a result, these distributions have correct stationary asymptotics. We show the possibility of numerical control of the accuracy of the proposed procedure. We consider the examples of relaxation of the probability characteristics of the amplitude of a self-oscillator and a parametric oscillator with a noise pump. The evolution of the amplitude probability distribution is found.     

Fluctuations and stability of stationary non-equilibrium systems in detailed balance

A generalized thermodynamic potential for Markoffian systems with detailed balance and far from thermal equilibrium has been derived in a previous paper. It was shown that the principle of detailed balance is equivalent to a set of conditions fulfilled by this potential (“potential conditions”). The properties of this potential allow us to extend the validity of a number of thermodynamic concepts well known for systems in or near thermal equilibrium to stationary states far from thermal equilibrium. The concept of symmetry breaking phase transitions for these systems is introduced in analogy to thermal equilibrium systems by considering the dependence of the stationary probability density of the system on a set of externally controlled parameters {λ}. A functional of the time dependent probability density of the system is defined in close analogy to the Gibb's definition of entropy. This functional has the properties of a Ljapunov functional of the governing Fokker-Planck equation showing the stability of the stationary probability density. The Langevin equations connected with the Fokker-Planck equation are considered. It is shown that, by means of the potential conditions, generalized “thermodynamic” fluxes and forces may be defined in such a way that the smoothly varying part of the Langevin equations (kinetic equations) constitutes a linear relation between fluxes and forces. The matrix of coefficients is given by the diffusion matrix of the Fokker-Planck equation. The symmetry relations which hold for this matrix due to the potential conditions then lead to the Onsager-Casimir symmetry relations extended to systems with detailed balance near stationary states far from thermal equilibrium. Finally it is shown that under certain additional assumptions the generalized thermodynamic potential may be used as a Ljapunov function of the kinetic equations.     

Polarimetric laser radar target classification

Imaging laser radar (ladar) systems have been developed for automatic target identification in surveillance systems. Ladar uses the range value at the target pixels to estimate the target's 3-D shape and identify the target. For targets in clutter and partially hidden targets, there are ambiguities in determining which pixels are on target that lead to uncertainties in determining the target's 3-D shape. An improvement is to use the polarization components of the reflected light. We describe the operation and preliminary evaluation of a polarization diverse imaging ladar system. Using a combination of intensity, range, and degree of polarization, we are better able to identify and distinguish the target from other objects of the same class.     

Combination of differential discrimination and direct discrimination in pulsed laser timeof-flight systems

The output amplitude of the differential circuit is studied for differential discrimination in pulsed laser time-offlight systems. Based on the studies of the probability of detection and the probability of false alarms, the minimum detectable input signal of differential discrimination can be calculated. The results indicate that the differential discrimination detectability of the small signal will be reduced. A combined discrimination is proposed in this Letter to improve the time resolution of the large signal and ensure the probability of detection of the small signal at the same time. A proper value of the circuit parameter is found to balance the time resolutions of the small and large signals.