球形粒子的散射和偏振特性研究

利用黎卡地贝塞尔函数模拟了不同粒子尺度的散射光强和偏振特性.当粒子尺度增加时,散射光强增加;水平偏振变得不对称,而垂直偏振没有变化;当粒子的折射率虚部增加时,散射光强减少.从粒子的这些散射特性和偏振特性,可以测量和分辨不同尺度的粒子.     

基于偏振成像和图像融合的目标识别技术

提出了一种基于偏振特征的目标识别技术.实验采用He-Ne激光作为照明光源,根据目标散射光偏振度的差异,利用DSP图像采集系统获取了目标的偏振图像,并利用图像融合技术计算了目标的Stokes图像和偏振度图像.结果显示:偏振成像有效地滤除了杂乱背景散射光的影响,明显提高了目标成像的对比度和分辨率.所以偏振成像技术可以有效地提高目标探测和识别效率.     

基于偏振散射对大气中炭黑颗粒物表征

基于光的偏振散射原理提出了一种对大气中炭黑颗粒物进行表征的测量方法.首先利用偏振光子散射的蒙特卡洛模拟方法寻找表征炭黑颗粒物属性的偏振特征参量,进而通过实验对特征参量进行验证.结果表明,获取的偏振参量对炭黑有较好的表征效果.此外,偏振表征不仅可以兼容现有非偏振散射仪器,提供更多颗粒物属性等信息,还可以减少探测角度,优化探测装置.     

海浪光散射特性的理论研究

用随机镜面模型建立分析海浪光散射特性的理论方法。计算了太阳光照射下不同海况海浪散射的空间分布变化趋势，表明随着海面均方根斜率增大，散射分布半峰宽度不断增大。     

基于双高斯拟合的目标激光偏振特性实验研究

对几种典型目标的后向散射光偏振度进行了测量和分析。基于探测光的Stokes 矢量描述,利用接收光路和发射光路的一体化设计,设计了典型目标偏振特性的激光探测实验装置;在不同偏振光入射角、不同粗糙度参数以及不同表面材质的条件下,对几种典型目标后向散射光的偏振度进行了测量;在实验的基础上对偏振度测量数据进行了双高斯拟合和分析,得出了目标后向散射光偏振度与双高斯函数基本吻合以及基于后向散射光偏振度可以区分不同属性目标的结论。     

舰船尾流气泡多重散射偏振特性研究

舰船尾流气泡的多次散射效应对光尾流探测领域的研究具有重要意义.针对水中气泡多次散射对后向散射光强以及偏振度的影响规律问题,基于矢量Monte Carlo方法,采用欧拉矢量法对光子在水中气泡后向散射偏振态进行跟踪,对比分析了线偏振、圆偏振激光入射情况下,不同散射次数回波信号在强度和偏振度特性上的差异性,验证了欧拉矢量法用于光尾流探测仿真领域的可行性.     

光纤后向拉曼散射的温度特性及其应用

利用波长为９０５ｎｍ，ＧａＡＳ大功率半导体脉冲激光器为泵浦光源，采用光时域反射ＯＴＤＲ（ＯｐｔｉｃａｌＴｉｍｅ－ＤｏｍａｉｎＲｅｆｌｅｃｔｏｍｅｔｒｙ）技术，以及高速采样平均技术对芯径为５０／１２５μｍ，１ｋｍ长的ＧＩ多模光纤的后向散射光光谱进行了分析与测量．着重研究了光谱成份中，强度仅为入射光强的１０－８～１０－９极其微弱的反斯托克斯散射光的温度特性及其应用—分布光纤温度传感系统．     

基于MB模型的简化偏振BRDF模型建立与仿真

偏振BRDF模型的计算往往非常复杂,为了简准确地获取伪装目标和背景的反射光偏振度差值,采用特殊值法和理想化方法对Maxwell-Beard BRDF模型中的微面元分布函数和遮蔽函数进行简化,使微面元分布函数较Torrance-Sparrow模型准确,较Maxwell-Beard模型更简单.然后利用Fresnel反射中物体对光线平行分量和竖直分量反射率不同的性质,采用物理理论分析的方法计算得到表示反射过程的Muller矩阵,并建立了其矢量BRDF模型.针对面内反射,利用Matlab对模型进行模拟,仿真结果证明:模型可以描述粗糙表面反射偏振特性.研究结果对研究粗糙表面反射偏振特性的影响因素及伪装目标偏振探测有一定的理论和实践意义.     

紧聚焦的角向偏振艾里光束产生超分辨光针

为了研究角向偏振艾里光束的紧聚焦特性,采用理查德-沃夫矢量衍射理论分析优化了艾里光束的指数衰减因子、主环半径与比例因子对其入射光场分布的影响;分别研究了角向偏振艾里光束聚焦场分布与涡旋滤波器调制的角向偏振艾里光束的聚焦场分布,得到亚波长的角向中空场分布与亮场分布,实验结果与理论模拟基本一致.进一步利用粒子群算法设计多环...     

折射式起偏器的密勒矩阵表示及偏振度分析

为了研究折射式起偏器的密勒矩阵表达式,以矩阵光学中关于斯托克斯矢量和密勒矩阵的有关理论为基础,通过理论运算导出了折射式起偏器的密勒矩阵的一般表达式;探讨了自然光以任意角度入射折射式起偏器的情况下透射光的斯托克斯矢量表示及偏振度所满足的公式;绘制了以布儒斯特角入射时透射光偏振度与介质折射率及介质层数的关系曲线。结果表明,在以布氏角入射折射式起偏器的前提下,增大介质的折射率和介质层数更容易获得较高的偏振度。这一研究结果对多层介质膜器件同样适用,具有一定的现实参考意义。     

研究液体表面特性的激光动态光散射系统

本文介绍了我们已建立的用微机控制的激光散射实验系统,并用已知常规液体及低介面张力的二相微乳体系样品测量,实验结果与预期相符。     

海面正置长方体目标复合散射极化特征

为分析海面上长方体目标的极化特征,通过极化特征图讨论了长方体目标尺寸参数和海面风速、风向对于复合极化散射的影响.计算结果显示入射角和目标尺寸足够大的情况下,二次散射更为突出,对应的极化特征图具有明显的二面角特点.侧风将会改变极化特征图的对称性.     

Polarization of light scattered by vegetation

The potential information in polarization data of both single leaves and plant canopies is investigated. Measurements demonstrate the relationship between polarization data and various optical and botanical properties of both pieces of foliage and plant canopies. The results provide a basis for gaining fundamental understanding of how light is scattered and polarized by a plant canopy. The results show the polarized and nonpolarized portions of the light scattered by a remotely sensed ground scene potentially are independent sources of information for discriminating species and assessing the condition of plant canopies.     

Polymer-based scattering layers for internal light extraction from organic light emitting diodes

Efficient light extraction for organic light emitting diodes (OLED) using scalable processes and low-cost materials are important prerequisites for the future commercialization of OLED lighting devices. The light-extraction technology exhibited in this paper uses polymer-based high-refractive index scattering layers processed from solution. The scatter matrix formulation incorporates two types of nanoparticles for refractive index tuning and scattering, respectively. Planarization by the same material in order to reduce surface defects was critical for achieving highly increased device yield. Highly efficient and defect-free large-area (1.8 cm²) white OLED devices were fabricated on top of the scattering layer in a bottom emitter configuration. Light extraction enhancement leads to an overall efficiency gain of up to 81% for luminances of 5000 cd m⁻².     

Inelastic light scattering from electronic excitations in quantum dots

A review is given of progress in our understanding of the electronic excitations in semiconductor quantum dots as studied by inelastic light scattering spectroscopy. Such experiments have revealed the characteristics of single particle, charge density, and spin density excitations of many-electron dots in zero and applied magnetic fields. Theoretical calculations, which reveal an electronic shell structure, are in general accord with the experimental results. Although the behaviour in a magnetic field is extremely complex, it is now feasible to study collective excitations from a range of strongly correlated ground states using this technique.     

一种红细胞光散射模型的研究

针对球形细胞模型理论与双凹圆盘状的红细胞在实际光散射法检测中的差异,根据细胞的类别特征,提出以扁椭球模型来模拟红细胞,以Rayleigh-Debye-Gans近似理论为基础,引入扁椭球的体极化率,得到了扁椭球模型的散射光公式,并进行数值模拟,研究其光散射特性。结果表明,扁椭球模型更精确地反映了红细胞光散射的真实情况,同时其前向、侧向及后向光散射精细谱的呈现,可以较容易地辨别病理状态的红细胞,能够较好地提高医学检验及诊断的精度,并可以应用于对红细胞的变形性研究。     

Polarization properties of stimulated Brillouin scattering insingle-mode fibers

The polarization properties of stimulated brillouin scattering (SBS) in low birefringent optical fibers were evaluated using Stokes calculus. It was found that the Brillouin gain for orthogonally polarized pump and probe wave is half (in dB) of the gain for identical polarization, and not equal as often mentioned in literature. Therefore the polarization factor is K=1_1/2 for complete polarization scrambling, and not K=2. The spontaneous SBS has the same state of polarization as the pump, and its degree of polarization is 33.3% for low pump powers and near 100% for high pump powers. The experimental results agree very well with the calculations     

A perfused tissue phantom for ultrasound hyperthermia

A perfused tissue phantom, developed as a tool for analyzing the performance of ultrasound hyperthermia applicators, was investigated. The phantom, consisting of a fixed porcine kidney with thermocouples placed throughout the tissue, was perfused with degassed water by a variable flow rate pump. The phantom was insonated by an unfocused multielement ultrasound applicator and the temperatures in the phantom were recorded. The results indicate that for testing protocols where tissue phantoms are needed, the fixed kidney preparation offers an opportunity to use a more realistic phantom than has previously been available to assess the heating performance of ultrasound hyperthermia applicators.     

Light extraction from OLEDs for lighting applications through light scattering

OLEDs are gaining increasing interest for lighting applications as large-area light sources. Their lifetime and overall efficiency can be increased by the optimization of light outcoupling.In this article, scattering films on the viewer’s side of the substrate to increase the outcoupling efficiency of OLEDs for lighting applications are examined. Experimental results show that the increase of outcoupling efficiency is dependent from the absolute number of scattering particles in the matrix.Theoretical considerations expect an increase of outcoupling efficiency of up to 70%. Experimental results yield an increase of outcoupling efficiency of about 22%. A software model based on raytracing to simulate light outcoupling from OLEDs through a scattering layer is introduced to gain a deeper understanding of the light extraction mechanism. We found that the scattering anisotropy factor g determined using the Henyey–Greenstein phase function and the effective absorbance of the OLED device have strong impact on outcoupling efficiency.