Visible imaging characteristics of space targets oriented to on-orbit observation

This research presents the modelling and simulation method of the visible imaging characteristics for a space target. The surface of the space target is divided into facets in order to improve the modelling precision. Based on the consideration of the mixing-material of the solar panel, the measuring method of the equivalent BRDF is proposed, from which we achieve the measurement and modelling of the equivalent BRDF of the solar panel. To reflect the operate mode of the solar panel pointing to the sun, a calculation method of panel normal vector is proposed based on the principle of maximum light efficiency. The simulation of the detection signal is carried out according to the OTF and the photoelectric response model. The results show that the proposed modelling method can simulate the imaging characteristics of space targets with a complex structure, as well as correctly reflect the movement characteristics of the on-orbit satellite.     

高速飞行器气动光学传输效应的工程计算方法

气动光学传输效应对飞行器光学成像探测系统的性能有着十分重要的影响，它使探测器接受的图像产生偏移、抖动和模糊。文章分析了目标光线通过流场时的光学传输特性，建立了流场光学传输特性的工程计算模型，描述了气动光学传输效应对成像探测系统影响的经验模型。在此基础上，对气动光学传输效应产生的像偏移、抖动和模糊进行了数值仿真，仿真结果表明，气动光学传输效应对成像探测系统的影响与飞行器的飞行参数、成像探测系统参数和探测器积分时间等密切相关。     

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.     

EMCCD用于空间生物光成像探测的可行性分析

生物光检测技术在地面的应用日益广泛,而空间生物光检测技术还处在对光强较强的生物光检测的阶段.空间生命科学研究的持续发展对微弱生物光检测技术提出需求.本文对比分析几种微弱光探测技术,总结了EMCCD在空间应用的技术优势,并提出了基于EMCCD的空间微弱生物光成像检测系统的方案.从目标亮度、探测器光敏面照度及探测器制冷等角度分析了弱信号的获取和系统信噪比,对基于EMCCD技术的空间生物光成像检测系统的可行陛和检测能力进行了分析论证.     

大视场可见光目标模拟器光学系统设计

具有特定视场的动态可见光目标模拟器是可见光成像系统测试与评估的关键设备,该模拟器的准直投影光学系统决定了基于数字微镜阵列(DMD)的动态景象投射器的性能。根据成像系统测试与评估需求,本文对可见光准直投影光学系统进行设计。基于对投影光学系统的参数计算,设计了视场58°的大视场可见光目标模拟器光学系统。将设计结果与成像光学系统进行匹配仿真,获得了良好的配合效果。通过对所研制的系统进行测试,实验结果表明所设计的光学系统完全满足模拟器的要求和对动态场景的仿真需求。     

天基光学空间目标监视信息处理技术分析

SBV是目前已成功应用于空间目标监视的典型天基光学传感器,通过被动探测空间目标反射的太阳光线辐射,完成对其探测、捕获和跟踪,并收集各种空间目标的观测数据.本文首先对SBV特点和性能进行介绍,然后以其为系统原型对天基光学空间目标监视信息处理流程和特点进行分析,提取相应关键技术,包括目标检测与恒星提取、编目维护与更新以及目标亮度特性分析等,并就其技术难点和发展趋势进行探讨.     

基于BRDF的在轨卫星反射特性

基于卫星的背景特性、材料特性、轨道特性及太阳帆板与卫星本体的相对运动特性,研究了在轨卫星的可见光反射特性.实验测量了三种卫星表面常用材料典型角度的双向反射分布函数,并构建了三种材料改进的SunBRDF模型.提出了一种单自由度运动的太阳帆板入射光线矢量计算方法.根据卫星的几何尺寸和表面材料特性,仿真获得了在轨卫星不同观测...     

反射式光纤传感器光纤对输出特性的数学模型

从反我纤传感器中最基本的光纤对入手，以光度学原理为基础，建立了该传感器在镜反射时的输出特性数学模型。在此模型的基础上，利用计算机给出了光纤传感器输出特性的仿真结果并进一步讨论了输出特性与各参数之间的关系。     

用梯度LOG算子实现小目标实时跟踪

为提高复杂背景条件下小目标检测及跟踪的稳定性,提出了一种基于梯度LOG算子的光团目标检测跟踪算法,首先建立了梯度图像中小目标的成像模型,能够较好地适应背景光照变化.然后根据尺度空间的基本理论构造了一种针对该成像模型的目标检测算子,分析并证明了该算子具有尺度不变性的优点,设计并实现了基于梯度LOG算子的小目标跟踪方案,实验结果表明:梯度LOG算子能够较好地跟踪复杂背景中的光团目标,定位精度可达亚像素级,且具有计算量小,抗噪声能力强等优点.     

Monte Carlo modeling of an integrating sphere reflectometer

The Monte Carlo method has been applied to numerical modeling of an integrating sphere designed for hemispherical-directional reflectance factor measurements. It is shown that a conventional algorithm of backward ray tracing used for estimation of characteristics of the radiation field at a given point has slow convergence for small source-to-sphere-diameter ratios. A newly developed algorithm that substantially improves the convergence by calculation of direct source-induced irradiation for every point of diffuse reflection of rays traced is described. The method developed is applied to an integrating sphere reflectometer for the visible and infrared spectral ranges. Parametric studies of hemispherical radiance distributions for radiation incident onto the sample center were performed. The deviations of measured sample reflectance from the actual reflectance as a result of various factors were computed. The accuracy of the results, adequacy of the reflectance model, and other important aspects of the algorithm implementation are discussed.     

Modeling of solar-radiation transfer in the spherical system of atmosphere-earth’s surface

The study gives a characteristic of the developed model of solar-radiation transfer in the spherical system atmosphere-earth’s surface. Account is taken of the vertical profiles of the aerosol and gas components of the atmosphere, the anisotropy of the reflection of the earth’s mantle, the properties of the relief of the earth’s surface, the characteristics of the wind wave, and the optical properties of the aqueous medium. The problem of radiation transfer is considered in the approximation of the small-angle modification of the method of spherical harmonics. The polar and azimuthal distributions of the components of the Stokes vector are obtained. The integral radiation characteristics and the temperature and rate of heating of the medium at various levels are determined within the framework of a general calculation scheme.     

采用仿射变换的红外与可见光图像配准方法

图像配准是图像融合技术的基本环节和首要问题。针对红外和可见光图像的配准问题,分析了两者配准的特点。引入6参数的仿射变换模型来描述3D空间中的目标,分析了通常采用的4参数模型的不完备性。利用模型计算配准参数,并用最小二乘法达到用多个配准点拟合出最优参数解的目的。实验结果表明,此方法可以很好地消除红外和可见光图像之间的差异。     

Polarization-based index of refraction and reflection angle estimation for remote sensing applications

A passive-polarization-based imaging system records the polarization state of light reflected by objects that are illuminated with an unpolarized and generally uncontrolled source. Such systems can be useful in many remote sensing applications including target detection, object segmentation, and material classification. We present a method to jointly estimate the complex index of refraction and the reflection angle (reflected zenith angle) of a target from multiple measurements collected by a passive polarimeter. An expression for the degree of polarization is derived from the microfacet polarimetric bidirectional reflectance model for the case of scattering in the plane of incidence. Using this expression, we develop a nonlinear least-squares estimation algorithm for extracting an apparent index of refraction and the reflection angle from a set of polarization measurements collected from multiple source positions. Computer simulation results show that the estimation accuracy generally improves with an increasing number of source position measurements. Laboratory results indicate that the proposed method is effective for recovering the reflection angle and that the estimated index of refraction provides a feature vector that is robust to the reflection angle.     

Features of photoacoustic transformation in microporous nanocrystalline silicon

Results of a study of the photoacoustic transformation in microporous nanocrystalline silicon are described. The amplitude-frequency and phase-frequency characteristics of the photoacoustic signal from microporous silicon samples on a monocrystalline substrate exposed to illumination at various wavelengths are experimentally determined. Informative response was measured by the gas-microphone and piezoelectric detection methods. In terms of the proposed mathematical model, it is shown that the difference in the parameters of the photoacoustic signal for different wavelengths of exciting radiation is attributed to a shift of the fundamental absorption edge in nanocrystalline silicon. It is pointed out that the piezoelectric detection method is more sensitive to changes in the thermophysical and optical parameters of the porous layer.     

玻璃空间电离辐照着色研究

对几种玻璃(K9-HL玻璃、JGS3石英玻璃、K509玻璃以及JGS1石英玻璃)在电离辐照(质子、电子)作用下的光学稳定性进行了系统研究, 并以此为基础, 通过空间电离辐照在玻璃作用的模拟计算, 对这几种玻璃在轨(近地点350 km, 远地点425 km, 轨道倾角51.6^o)光学寿命进行了预测. 在该轨道使用10年时, K9-HL玻璃可见光透过率可能出现明显下降, 而JGS3石英玻璃、K509玻璃以及JGS1石英玻璃的可见光透过率保持不变或变化很小. 由于绝大多数空间粒子穿透能力小, 空间电离辐照仅能造成玻璃表层的着色. 因此, 长期在轨航天器舷窗可加一防电离辐照层以减少内层玻璃接受的电离辐照量, 而该层玻璃可采用石英玻璃.     

Characterization of near-field optical probes

Radiation and collection characteristics of four different near-field optical-fiber probes, namely, three uncoated probes and an aluminum-coated small-aperture probe, are investigated and compared. Their radiation properties are characterized by observation of light-induced topography changes in a photosensitive film illuminated with the probes, and it is confirmed that the radiated optical field is unambiguously confined only for the coated probe. Near-field optical imaging of a standing evanescent-wave pattern is used to compare the detection characteristics of the probes, and it is concluded that, for the imaging of optical-field intensity distributions containing predominantly evanescent-wave components, a sharp uncoated tip is the probe of choice. Complementary results obtained with optical phase-conjugation experiments with the uncoated probes are discussed in relation to the probe characterization.     

矢量法在计算空间目标地面照度中的应用

从基本辐射理论出发，推导了空间漫反射目标地面照度的计算公式，详细讲解了采用矢量法对该公式中的积分进行计算的过程，矢量法可应用于任何外形能写出函数关系的目标。以球为例，实际计算了其星等值，并将结果与其他方法计算的结果进行了比较，它们完全一致。     

Model Based Incipient Fault Detection for Gear Drives

1 IntroductionWth the develoPment of science and technology, modem machine alld equipment become moeand moe comPlex, and this affects the reliability of the systems. Being the contrOlled obect, thegear drives in highly automated systems often have faults subected to unexpected change ofsome parameter causcd by change of environment temPeratUre, OPerating condition and loads, etc.The change of some parameter may tend to degrade overall system performance, and may Inakthe system break down in…     

Growth and characterization of benzaldehyde 4-nitro phenyl hydrazone (BPH) single crystal: A proficient second order nonlinear optical material

The crystals (benzaldehyde 4-nitro phenyl hydrazone (BPH)) appropriate for NLO appliance were grown by the slow cooling method. The solubility and metastable zone width measurement of BPH specimen was studied. The material crystallizes in the monoclinic crystal system with noncentrosymmetric space group of Cc. The optical precision in the whole visible region was found to be excellent for non-linear optical claim. Excellence of the grown crystal is ascertained by the HRXRD and etching studies. Laser Damage Threshold and Photoluminescence studies designate that the grown crystal contains less imperfection. The mechanical behaviour of BPH sample at different temperatures was investigated to determine the hardness stability of the grown specimen. The piezoelectric temperament and the relative Second Harmonic Generation (for diverse particle sizes) of the material were also studied. The dielectric studies were executed at varied temperatures and frequencies to investigate the electrical properties. Photoconductivity measurement enumerates consummate of inducing dipoles due to strong incident radiation and also divulge the nonlinear behaviour of the material. The third order nonlinear optical properties of BPH crystals were deliberate by Z-scan method.     

光纤作为量子信道的性能

本文研究光纤作为量子信道在密波分复用时模式间非线性干扰造成的信道噪声的性质 ,和光纤量子信道在该噪声下的经典容量 .用位移算符方法计算量子噪声的累加 ,同时建立了有衰减和噪声时的信道的量子模型 .本文论证如果干扰是各其他模式独立而均等的贡献的叠加 ,信道噪声是热辐射噪声类型的 ,并求出了在给定参数的情况下的经典容量