【作者】 程玉宝；

【导师】 刘上乾；

【作者基本信息】 西安电子科技大学 ， 物理电子学， 2005， 博士

【摘要】 面对日益严重的激光威胁,世界各国都在加速发展激光告警技术的研究和激光告警装备的研制。根据用于地面大型军事目标激光告警的军事预研项目——“大范围新型激光告警系统的研制”的要求,本文对该系统研制过程中涉及到的若干技术问题作了较为深入的研究,主要研究成果如下：通过对激光在大气传输中散射效应的分析,运用米氏散射理论,推导出了大气散射激光辐照度随离轴距离变化的数学模型,通过数值计算和理论分析,得到了1.06μm激光在都市郊区大气模型条件下的散射信号时域特征：大气散射激光的最大辐照度随离轴距离的增大近似地按反比规律缓慢下降；大气能见度的不同只会影响散射强度的大小,而不影响散射强度的分布规律等。这些特征为1.06μm激光散射告警器的研制提供了理论依据。由于告警系统的虚警概率随散射告警器数目的增多而增大,为了降低大范围新型激光告警系统的虚警概率,针对炮火闪光、太阳反射光等干扰因素在一定的时间内具有单次性的特点,设计了一种计数并计时工作的积累检测器,提出了一种将多元相关探测和该积累检测器相结合的检测模型,并采用激光威胁等级判断告警方式,有效地降低了散射告警器的虚警概率。在研究和归纳比较激光波长相干探测各种方案的优缺点,以及通过深入分析劈尖干涉条纹的定域和条纹间距与入射激光波长关系的基础上,提出了在直射告警器中采用基于劈尖干涉的激光波长探测新方案。采用线阵型电荷耦合器件(CCD)将等厚干涉条纹转换为时域周期信号,运用离散傅里叶变换(DFT)求解条纹间距,便可计算出激光波长。为提高对波长的探测精度,推导出了相应的DFT离散误差修正公式,仿真实验结果验证了其有效性。为提高直射告警器的反应速度,减少运算时间,提出了使用数字滤波器法快速探测制导激光波长的设计思想,并推导出了数字滤波算法的迭代公式,研制出了能快速探测多种制导激光波长的数字滤波器,有效地提高了告警器的反应速度。针对CCD器件非均匀性引入的固有噪声对探测入射激光微弱信号的不良影响,在分析CCD器件非均匀性产生机理的基础上,提出了在直射告警器中使用非均匀性校正技术的方案,达到了提高系统灵敏度和增大其作用距离的目的。通过分析激光波长、重频、能量变化率等技术参数在描述和判别激光威胁源时的不确定性,提出了基于模糊决策的激光威胁源识别的设计思想。运用模糊决策理论,建立了激光能量、波长、重频等技术参数的模糊化数学模型,设计出了基于激光威胁源识别的模糊决策规则库,实现了对激光威胁源的准确识别。更多还原

【Abstract】 As laser menace is increasing quickly, laser warning technologies are being researched and the laser warning equipments are being rapidly developed all over the world. To meet the demand of the military project, "Development of a Novel Laser Warning System Used for Large-Sized Land Targets", some problems regarding the laser warning system are studied in this dissertation. Some valuable results are obtained which are summarized as follows:By analyzing the scattering effects caused by the transmission of laser through the atmosphere and using Mie’s scattering theory, the mathematical model that presents the relation between laser irradiance of atmospheric scattering is derived. The time domain characteristics of the scattering signal distribution of 1.06μm laser under the condition of city suburb model are obtained by theoretical analysis and numerical calculation. That is, the maximum intensity of aerial scattering laser decreases slowly with the abaxial distance of detector and is inversely proportional to the distance; and the aerial visibility only affects the scattering intensity, instead of the distribution of scattering intensity. These characteristics provide the theoretical basis for the development of the scattering laser warning system at 1.06μm.Due to the fact that the false alarm probability increases with the number of warning unit and interference factors such as gunfire flash and reflection light of the sun are of single time characteristics, a accumulating detector that has the function of counting and timing is designed and a detecting model that combines multiple-unit correlation detection and the aforementioned accumulating detector is presented. As a consequence, such system can effectively reduce false alarm probability by using threat grade warning.On the basis of extensive study and summarization various coherent detecting methods, a new scheme to measure laser wavelength is presented by analyzing the localization of the interference stripes of optical wedge and the relation of the stripes’interval to the incident laser wavelength. When parallel laser beam is perpendicularly incident onto an optical wedge, some equal-width stripes occur on the surface of the wedge whose space period can be transformed into time domain period by linear charge coupled device (CCD). The incident laser wavelength can be calculated from the intervals of the stripes obtained by Discrete Fourier Transform (DFT). In order to improve the measuring precision of the laser wavelength, the modified formula, which has a universal purpose, of the DFT’s discrete error is derived. The validity of the method is validated by experimental results.A method of quick measuring several missile-guiding laser wavelengths is proposed by digital filters so as to raise the response speed and reduce the computing time of laser warning receiver. In the signal processing of laser warning receiver, the digital filters that are designed by using the digital filter iterative formula derived from DFT can quickly detect several missile-guiding laser wavelengths. The method can effectively raise the response speed.Considering the effects of the inherent noise caused by the non-uniformity of CCD on the detection of weak signal of incident laser, the generation mechanism and the correction algorithms of the non-uniformity of CCD are studied. The idea that the techniques of non-uniformity correction are applied in laser warning receiver is proposed to improve its detection sensitivity and increase its action distance.The idea of fuzzy-decision-based laser menace source recognition is presented on the basis of analyzing the uncertainty of the technical parameters, such as the laser energy, the laser wavelength and the repetitive frequency, to recognize menace source. The mathematical fuzzy models of laser technique parameters, such as the laser energy, the laser wavelength and the repetitive frequency, are set up, and fuzzy rule library of laser menace source recognition is designed by using fuzzy decision theory. Therefore, laser menace source can be identified correctly.更多还原