共查询到20条相似文献,搜索用时 15 毫秒
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Chen Hui Wu Zhensen Bai Lu 《International Journal of Infrared and Millimeter Waves》2004,25(8):1211-1219
Analytical expression for the two-frequency mutual coherence function of the infrared laser pulse scattering from randomly rough surfaces is presented based on the Kirchhoff approximation. Scattered pulse shapes are calculated at 10.6m as the Fourier transform of the two-frequency mutual coherent function. It is shown that the root-mean-square height of rough surface greatly influences on results and the scattered pulse power mainly comes from the specular direction with small rms height. 相似文献
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根据广义米氏理论,将入射的高斯波束按矢量球谐函数展开,获得了波束因子(展开系数)gmn,TM和gmn,TE的一般表达式。应用gmn的局域近结果和散射系数anm和bnm的迭代公式与算法,研究了多层有耗介质球的光散射。讨论了波束宽度与球形粒子的尺寸和位置对散射系数和散射强度角分布的影响。 相似文献
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两个相邻目标对平面波、高斯波束的光散射 总被引:3,自引:0,他引:3
基于等效原理和互易性定理研究了两个靠近目标对平面波、高斯波束的光散射问题,给出了这一复合光散射模型的二阶散射结果。通常一阶散射结果容易求解,但由于耦合效应的复杂性,很难给出二阶散射结果的解析形式。为了解决这一问题,应用互易性定理给出了求解任意相邻介质目标二阶散射场的公式,同时借助等效原理将求解散射场公式中的体积分简化为面积分的形式,从而降低了求解难度。求解了两相邻球形粒子的复合散射场,并将求解结果与应用时域积分方程法求得的结果进行了比较。同时,还讨论了束腰半径、目标位置对散射截面及偏振度的影响。 相似文献
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粗糙表面激光散射特性的理论研究 总被引:8,自引:0,他引:8
用矢量微扰动方法分析激光束在粗糙表面上散射的分布特性。详细讨论高斯光束的角谱和适用于准直激光束散射问题的波前分割概念认为,当用入射总功率作归一化因子时,准直粗激光束散射可近似地作为平面波处理,而细激光束散射则与平面波存在很大的差异,利用所得结果讨论了一维粗糙表面的激光隐身作用及椭圆偏振光入射时镜反射方向和后向散射场的偏振态。最后介绍两种线偏振光在粗糙表面上散射分布的差异。实验验证了主要结论。 相似文献
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Zhensen Wu Kun Song Liyan Qi 《International Journal of Infrared and Millimeter Waves》2000,21(2):247-254
The laser bistatic scattering from some deeply rough plane samples are measured by using of the automated scattering measurement system. We observe the backscattering enhancement, which is confined to a narrow cone around the antispecular direction, and discuss the influences of roughness and dielectric properties on them. 相似文献
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任意形状凸粗糙物体高斯光束相干散射研究 总被引:4,自引:3,他引:1
研究了任意形状凸粗糙物体对高斯光束的相干散射特性。由平面波谱展开法推导出粗糙面高斯波束散射场表达式.并根据物理光学近似和稳相法原理得到相干散射截面的理论公式。与平面波解不同的是,在公式中引入了波束因子这一表征波束作用的重要参量,该参量与束腰半径、束腰中心与物体中心距离和物体照射面积以及入射、散射方向有关。最后数值计算了1.06μm激光波束对粗糙球的散射,分析了波束因子.介电常量和极化状态对红外激光相干散射截面的影响,重点讨论了波束因子的变化规律。分析表明.当波束半径远大于物体尺寸时,波束入射的结果可退化到平面波情况。 相似文献
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Lu Bai Zhensen Wu Min Zhang Kuan Fang Ren G. Gréhan 《International Journal of Infrared and Millimeter Waves》2004,25(8):1221-1230
Multi-spheres scattering has been fully discussed, but almost all kinds of these researches are in plane wave. The special case of an incident shaped beam is introduced in this paper. While some numerical results for cluster spheres illuminated on the axis of a shaped beam in millimeter waves are presented. Finally, results of numerical computations illuminated by a shape beam in different beam waist radius are compared with those for a plane wave illumination. 相似文献
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根据粗糙面散射理论,用相位微扰法推导出了从随机粗糙介质表面散射的激光雷达散射截面的理论计算公式,计算了几种粗糙表面样品在1.06μm下的单位面积激光雷达散射截面,数值结果与实验数据基本吻合。 相似文献
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The scattering and focusing characteristics of a Gaussian beam with phase distribution is studied by a stepped index Luneberg lens. A model experiment was performed using a six-layer spherical lens. Two kinds of beams, that is, broad and narrow beam are examined for the incident Gaussian beam. We find that focusing effect of a narrow beam is wholly lower than that of a broad beam. The focal point is also shifted toward outer of sphere because of phase lag for the beam source. The spot size equals almost the wavelength for the various beam parameters. 相似文献
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Fractal Characteristics Investigation on Light Scattering from Two Dimensional Rough Surface 总被引:2,自引:0,他引:2
A normalized two dimensional band-limited Weierstrass fractal function is used for modeling the rough surface. Based on Kirchhoff theory, an analytic solution of the average scattering field and the variance of scattering intensity are derived with emphasis on examining the relation of fractal dimension with the scattering pattern. The important conclusion is obtained that the diffracted envelope slopes of scattering pattern can be approximated to a slope of linear equation. 相似文献
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LIU Yingzhuang PENG Fuyuan ZHU Yaoting ZHU Guangxi MA Yong 《Chinese Journal of Lasers》2001,10(2):149-152
1 Introduction Howtoevaluatethebackwardscatteringpowerofacollimated green bluelaserbeamtransmittingintheseawaterisofgreatimportantinthecourseofairbornelaserdetectingunderwatertarget,andthebaseofthecalculationofreceivedpoweranddeterminationofthesystemp… 相似文献
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不同表面激光双向反射分布函数的实验研究 总被引:22,自引:0,他引:22
根据粗糙面电磁散射理论讨论了粗糙表面双向反射分布函数(BRDF)和单位面积激光雷达截面的关系。测量不同粗糙度金板、铝基、钢基和涂层样片在0.63μm的双向反射分布函数。分析了高度起伏均方根δ,斜率起伏均方根s,介电常数对双向反射分布函数的影响。最后,将部分粗糙样片的双向反射分布函数理论计算结果与实验数据比较,两者有良好的吻合。 相似文献
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Based on the orthogonalities of the vector wave functions, the expressions of scattering fields are developed as the particle in the zero order field and in the first order fields of x, y, and z, respectively. A general relation between the expansion coefficients of scattering field and incident field is presented. Taking the elliptical beam for example, the scattering property of a particle in beam is investigated. After analyzing the effects of the beam waist, irradiating distance, etc. on scattering property, the validity of the proposed algorithm is demonstrated. Results show that the beam waist may improve the particle identification property and the particle has a strong scattering both in the forward direction and in the backward direction. The method proposed is simple and is a new way of researching the scattering from particles in electromagnetic beams. 相似文献
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为了研究高功率激光传输过程中不透明颗粒引起的光束调制,通过分析这些不透明颗粒的形状和分布特点,建立了位置呈随机分布的高斯状散射点模型,从光束的衍射理论和干涉叠加理论出发,得到该模型下散射点对传输光束质量影响的解析式。数值分析了高斯状散射点的大小、密度、散射面积比及其传输距离对输出光束的近场分布、位相分布和光束透过率的影响,结果显示亚毫米量级散射点的衍射效应引起最大调制可达1.4,光学元件散射面积比小于0.003时才能满足元件透过率大于99.5%的需求。该结果可用于评价高功率激光装置光学元件的加工状况,并对光学元件加工要求和激光装置的洁净度要求有指导意义。 相似文献
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S. Van den Bulcke L. Zhang A. Franchois J. M. Geffrin J. Stiens 《International Journal of Infrared and Millimeter Waves》2008,29(11):1038-1047
For the development of millimeter wave imaging systems, it is important to be able to simulate some representative scattering
configurations. Typically, Gaussian beams are used in active imaging systems. Since these beams only illuminate a spatially
limited region, many objects can be treated as infinitely long 2D (in)homogenous cylinders. However, the incident Gaussian
beams have a 3D character. Therefore, a dedicated 2.5D scattering simulator was developed. In this paper, simulation results
obtained with this simulator are compared to measurements obtained from a bi-static microwave set-up and from a W-band millimeter
wave set-up. Comparison of simulations and measurements proves that the 2.5D algorithm is a good simulation tool to study
scattering of long inhomogeneous cylinders, illuminated by 3D plane waves or 3D Gaussian beams under different elevation angles. 相似文献