大视场偏振CCD相机的偏振特性实验标定

大视场偏振CCD相机内部的多个光学表面会改变入射光的偏振状态,并且改变的程度与入射光的偏振态、视场角和方位角等有关,影响了仪器偏振测量精度,从而制约了偏振成像遥感数据的定量化应用水平。为解决这一问题,从考虑偏振效应的大视场偏振相机响应输出模型出发,研究模型参数的标定方法,通过设计试验获取了模型参数标定数据。将经过标定的大视场偏振CCD相机测试值和可调偏振度光源预设偏振度值进行对比,结果显示偏振相机在0°、15°、25°视场角下的偏振度测量平均误差不大于1.18%,远小于光学镜头自身的起偏度。消除偏振遥感仪器自身的偏振敏感性影响,为将来我国自主星载偏振遥感图像的定量化应用奠定基础。     

新型偏振特性因子及其传递关系的研究

偏振遥感图像通常可以采用强度、偏振度、偏振角或HIS柱形彩色空间表征目标偏振特性.本文通过建立光束在多层介质中传递的简单模型,找到一种新型偏振特性因子.此偏振特性因子所成图像是偏振度图像和偏振角图像信息复合的结果,其实质反映了偏振光束中的线偏振光的光强相对含量及它的偏振角方向.对伪装过的车牌进行偏振成像,实验表明此偏振特性因子可以用于特定环境下的伪装辨别.     

大面积有机半导体二维单晶膜偏振光电探测器件

偏振光电探测器件具有对光场矢量方向的探测能力, 可极大地丰富光电探测的信息维度, 揭露传统探测方法中所不能发现的隐藏信息, 因而在目标探测、地质遥感、机器视觉等方面具有重要的应用价值.利用材料结构的本征各向异性实现偏振响应, 有助于规避传统偏振探测需要耦合光学元件所导致的结构复杂和系统庞大等问题, 有助于实现器件的小型...     

人工目标偏振特征实验研究

简要介绍了多波段偏振成像技术，着重分析了某些主要人工目标的偏振特征。从光波的偏振传输特性着手，讨论了它们偏振态的空间变化和光谱变化，这些变化反映了目标的纹理特征、表面结构以及材料的类型。     

水色遥感的精确Rayleigh散射算法研究

偏振问题是卫星水色遥感需要解决的一个重要问题.通过对带偏振的辐射传输方程进行求解得到精确的Rayleigh散射计算结果,便可以对水色遥感器进行偏振修正.本研究将矢量辐射传输方程进行傅立叶展开,得到与方位角独立的矢量辐射传输方程,利用逐次散射法对其进行求解.本文给出了HY-1卫星上水色遥感器COCTS在不同观测角度和不同风速情况下的精确Rayleigh散射结果,并通过比较得到了在不同观测条件下Rayleigh散射结果之间的差异.     

基于边缘信息的偏振图像融合算法及评价

偏振遥感图像通常都采用强度、偏振度、偏振角来表征目标偏振特性.本文提出的基于边缘信息的偏振图像融合算法是将三幅偏振图像利用离散小波变换把图像分解成不同尺度的低频和高频部分,采用小波区域窗口和子区域窗口统计把小波系数分类成边缘和非边缘系数,通过这些方法进行有效的边缘细节信息提取.在融合处理中,低频图像的小波系数平均值作为融合后的低频系数,高频细节系数根据不同区域特征选择方法以及对应输入图像小波系数的窗口区域方差来确定融合后高频小波系数.仿真实验结果表明,这样使得融合后的图像细节更真实更丰富,图像的偏振特性体现更为充分,同时减少对源图像的预处理要求,使图像在整体上有较好的视觉效果.从而证明这种方法能够在保留图像微小细节方面获得满意的结果,且算法有效性优于其他的图像融合方法.     

热红外自发辐射偏振特性分析以及验证实验

光波经过反射后具有偏振特性,目前研究表明热红外自发辐射也具有偏振特性。本文结合基尔霍夫定律以及菲涅耳公式对热红外自发辐射偏振特性进行了初步的理论分析和建模仿真。在低温环境下,采取遮挡措施,进行了热红外自发辐射偏振特性的验证实验,对不同表面状态铝板以及太阳能电池板进行了自发辐射偏振数据的采集。实验结果表明:热红外自发辐射具有偏振特性,并与仿真结果具有一致的变化规律,热红外辐射偏振特性受目标表面粗糙度、材料影响并随着发射角的增加,偏振度不断增加。     

热红外偏振成像的目标探测技术研究

当目标与背景辐射强度接近时,传统的热红外成像系统无法有效区分背景与目标.基于光的偏振信息的目标探测技术国外已进行大量研究,在国内也越来越受重视,但尚处于初步研究阶段.采用非制冷热红外焦平面阵列,搭建热红外偏振成像系统,对特定场景中的典型目标开展了偏振成像实验,对图像进行了配准并对偏振度图像和强度图进行了融合.结果表明:热红外偏振成像较传统热红外成像对目标的探测有明显优势；采用基于HSI的偏振信息融合算法能综合反应目标特征,有利于提高图像质量,有利于远距离目标的探测与识别.     

光学偏振玻璃及其应用

近年来光学偏振玻璃器件在光显示、光通信等领域的应用越来越多，人们越来越关注偏振玻璃的特殊性能和制备工艺。文章详细介绍了光学偏振玻璃的发展历程，系统分析了光学偏振玻璃的偏光原理和偏振性能，介绍了偏振玻璃的制备和应用并讨论了偏振玻璃的发展前景。     

多波段偏振CCD相机的辐射定标研究

简要介绍了多波段偏振CCD相机系统。从分析面阵CCD探测器的光电响应不均匀性和三偏振方向光电响应的不一致性出发,介绍了基于辐射定标方法解决不一致性问题,得到辐射校正系数,提高了成像偏振信息的解析精度。     

Polarimetric imaging method for target enhancement in haze based on polarimetric retrieval

Polarimetric imaging has been proven to be an effective way in detecting the targets of interest in complicated surroundings by analyzing the polarization property, instead of the intensity, of the light emanating from the objects. Unfortunately, polarimetric imaging encounters difficulty when the surroundings are very scattered, where on the one hand the polarization property of the object light usually becomes very faint after a strong depolarized scattering process; on the other hand, the object light will be blended with the atmospheric light scattered by haze particles (airlight). In this paper, we propose a polarimetric imaging retrieval method that can be used for such challenging conditions. Firstly, the airlight radiance is estimated precisely. Then, the airlight is removed from the hazy images. Finally, the residual polarization property of the object light is regained, which ensures the validity of the polarimetric imaging method in these conditions. The experiments confirm that the proposed method is useful in enhancing polarimetric imaging detection in haze.     

A Minimalist Single-Layer Metasurface for Arbitrary and Full Control of Vector Vortex Beams

Vector vortex beams (VVBs) possess ubiquitous applications from particle trapping to quantum information. Recently, the bulky optical devices for generating VVBs have been miniaturized by using metasurfaces. Nevertheless, it is quite challenging for the metasurface-generated VVBs to possess arbitrary polarization and phase distributions. More critical is that the VVBs' annular intensity profiles demonstrated hitherto are dependent on topological charges and are hence not perfect, posing difficulties in spatially shared co-propagation of multiple vortex beams. Here, a single-layer metasurface to address all those aforementioned challenges in one go is proposed, which consists of two identical crystal-silicon nanoblocks with varying positions and rotation angles (i.e., four geometric parameters throughout). Those four geometric parameters are found to be adequate for independent and arbitrary control of the amplitude, phase, and polarization of light. Perfect VVBs with arbitrary polarization and phase distributions are successfully generated, and the constant intensity profiles independent of their topological charges and polarization orders are demonstrated. The proposed strategy casts a distinct perception that a minimalist design of just one single-layer metasurface can empower such robust and versatile control of VVBs. That provides promising opportunities for generating more complex vortex field for advanced applications in structural light, optical micromanipulation, and data communication.     

Comparison of the Gauss-Seidel spherical polarized radiative transfer code with other radiative transfer codes

Calculations that use the Gauss-Seidel method are presented of the diffusely scattered light in a spherical atmosphere with polarization fully included. Comparisons are made between this method and the Monte Carlo calculations of other researchers for spherical geometry in a pure Rayleigh atmosphere. Comparisons with plane-parallel atmospheres are also presented. Single-scatter intensity comparisons with spherical geometry show excellent agreement. When all orders of scattering are included, comparisons of polarization parameters I, Q and U as well as the plane of polarization show good agreement when allowances are made for the statistical variability inherent in the Monte Carlo method.     

Effects of turbid media optical properties on object visibility in subsurface polarization imaging

We studied the effectiveness of using polarized illumination and detection to enhance the visibility of targets buried in highly scattering media. The effects of background optical properties including scattering coefficient, absorption coefficient, and anisotropy on image visibility were examined. Both linearly and circularly polarized light were used in the imaging. Three different types of target were investigated: scattering, absorption, and reflection. The experimental results indicate that target visibility improvement achieved by a specific polarization method depends on both the background optical properties and the target type. By analyzing all polarization images, it is possible to reveal certain information about target or the scattering background.     

Effect of polarization state on electro-optic coupling and its application to polarization rotation

The effect of the polarization state on electro-optic coupling is studied by using the wave coupling theory of the linear electro-optic effect. The numerical results show that the polarization state obviously influences the electro-optic coupling. The conditions for realizing perfect coupling are emphasized. As an application of perfect coupling, a novel polarization rotator, which can rotate the polarization of a light beam with an arbitrary angle but keep the output intensity unchanged, is presented.     

A New Method for Spectral Performance Evaluation of a Chromatic and Achromatic Quarter-Wave Retarder

When a polarized polychromatic beam passes through a quarter-wave retarder, the constituent spectral components suffer different changes in the state of polarization. As a result, when the beam passes through an analyzer, the intensity of the resultant beam changes, depending on the orientation of the analyzer, state of polarization of the input beam, spectral and spatial intensity distribution of the source and the wavelength-dependent retardance of the quarter-wave retarder. The intensity variation of the resulting beam is theoretically and experimentally observed, with the variation of the azimuthal angle of the analyzer for film-type chromatic and prism-type achromatic quarter-wave retarders. The spectral performances of achromatic retarders are generally evaluated by measuring retardances at discrete wavelengths by using a monochromatic beam of light over the wavelength range of interest. In this study, a simple method is used for computing the fractional nonlinear polarization (FNLP) from theoretically and experimentally obtained intensity variations for evaluating the spectral performance of both achromatic and chromatic quarter-wave retarders operating over a broad spectral range in the visible region using a polychromatic beam of light. FNLP variation is also shown for a film-type chromatic quarter-wave retarder using a monochromatic source of light. The experimentally obtained values are compared with theoretical values and a good agreement is observed. The applications of the method for the performance evaluation of quarter-wave retarders are discussed.     

Kullback relative entropy and characterization of partially polarized optical waves

Different properties of partially polarized light are discussed using the Kullback relative entropy, which provides a physically meaningful measure of proximity between probability density functions (PDFs). For optical waves with a Gaussian PDF, the standard degree of polarization is a simple function of the Kullback relative entropy between the considered optical light and a totally depolarized light of the same intensity. It is shown that the Kullback relative entropies between different PDFs allow one to define other properties such as a degree of anisotropy and a degree of non-Gaussianity. It is also demonstrated that, in dimension three, the Kullback relative entropy between a partially polarized light and a totally depolarized light can lead to natural definitions of two degrees of polarization needed to characterize the polarization state. These analyses enlighten the physical meaning of partial polarization of light waves in terms of a measure of disorder provided by the Shannon entropy.     

Backscattering target detection in a turbid medium by polarization discrimination

We describe a method for increasing target contrast within a turbid medium by means of the polarization state of the scattered light. The backscattered Mueller matrices for various concentrations of 0.1-mum spherical scatterers were measured with and without a painted metal target. Simple discrimination based on detecting cross-polarized intensities is shown to be more effective than the use of total intensity information. As a result, the choice of polarization state is dictated primarily by the requirement to maximize depolarization at the target. This in general means that circularly polarized light is the optimum choice.     

A Method for the Optical Characterization of Thin Uniaxial Samples

An optical characterization procedure for small fragments of uniaxial materials is described involving the simple use of crossed polarizers with one polished face of the material. The reflectance at a fluid-uniaxial slab boundary beyond, but near, the critical angle of incident light is examined for linear incidence polarization using an orthogonal output polarizer. It is found that, as the crossed incident and output polarizers are rotated together, there are, for a given angle of incidence, particular polarization angles for which the reflectivity is a minimum. These angles give information on the optical tensor of the crystal under study. Further the intensity of the reflected light, for incidence angles beyond critical with the input and output polarizers crossed, has as a function of the incident polarization angle an oscillatory form which, when fitted to theory, can also yield the full uniaxial tensor of the material under study. This is confirmed experimentally for a thin single crystal of calcite with one polished face.