共查询到20条相似文献,搜索用时 0 毫秒
1.
2.
I. V. Rakut’ S. A. Pelyushenko A. S. Pelyushenko Yu. A. Zheleznyakov 《Radiophysics and Quantum Electronics》2005,48(10-11):792-800
We present the results of studies of backscattering characteristics of extended inhomogeneous media using a passive-active complex of near-field radio-wave imaging. The complex includes an 8-mm wavelength radiometer, a focusing antenna system, and a system of illumination of studied objects by a wideband noise signal. This radiometric complex is intended for the formation of a high-resolution radio image of the internal structure of spatially inhomogeneous media explored at distances commensurable with the size of the antenna aperture. The system of radio-wave imaging can be used for medical and biological studies of a human body and detection of extended objects hidden under the surface of a medium not transparent for visual observation, but partially transparent in the operating wavelength range. 相似文献
3.
4.
光学合成孔径成像技术及发展现状 总被引:1,自引:0,他引:1
5.
光学综合孔径望远镜成像分析及计算机仿真 总被引:13,自引:9,他引:4
阐述了光学综合孔径(OSA)望远镜成像原理以及综合孔径望远镜的几种实现形式;采用快速傅里叶变换(FFT)算法得到了任意子孔径综合模式下的点扩展函数(PSF)和光学传递函数(OTF)分布;从子孔径结构排列、共相位、图像恢复几个方面论述了光学综合孔径的成像特征。初步分析了稀疏率、填充因子、“实际截止频率”等因素对光学综合孔径望远镜成像的影响。分析和仿真结果表明:光学综合孔径通过相干成像不但可以突破传统单孔径系统的口径局限获得极高的成像分辨率,而且对于实现空间光学遥感系统轻量化和模块化都具有重要意义。 相似文献
6.
光学合成孔径成像技术发展概况 总被引:4,自引:0,他引:4
介绍了光学合成孔径成像技术的发展现状。简要阐明了合成孔径成像技术的原理和分类以及在光学波段的主要应用。归纳出了光学合成孔径成像技术的发展趋势:地基合成孔径系统向长基线方向发展;天基系统向超轻量化方向发展;图像处理正在成为系统不可分割的一部分;技术重点是从地基系统向天基系统转移,并被应用于更多领域。概括了光学合成孔径成像系统的各种应用方案及特点。与传统的光学系统相比,合成孔径成像技术具有如下特征和优点:可降低光学元件的加工难度和天基光学合成孔径成像系统的发射体积和重量,可节约发射费用。 相似文献
7.
8.
创建了地球场景数据集, 结合全极化微波辐射传输模型, 仿真了地球场景亮温. 基于自主推导的全极化天线温度方程, 通过GRASP9软件生成天线方向图, 模拟了辐射计的天线温度. 进而利用多元线性回归方法, 求取了天线交叉极化校正M矩阵, 实现了对星载极化相关型全极化微波辐射计天线交叉极化的校正. 试验结果表明: 天线温度与地球场景亮温之间具有良好的线性关系; 天线交叉极化对全极化微波辐射计正交通道亮温影响明显, 尤其以对垂直极化亮温误差的影响最为显著; 校正后各通道的天线交叉极化得到了有效的减小, 交叉极化优于-23 dB, 极化纯度大于99.5%, 采用M矩阵校正及消除天线温度中交叉极化亮温影响的方案是切实可行的. 该校正技术可以实现星载极化相关型全极化微波辐射计在轨运行后对于天线交叉极化的最终校正.
关键词:
全极化微波辐射计
天线交叉极化
天线温度方程
M矩阵')" href="#">M矩阵 相似文献
9.
Terahertz (THz) interferometric synthetic aperture tomography (TISAT) for confocal imaging within extended objects is demonstrated by combining attributes of synthetic aperture radar and optical coherence tomography. Algorithms recently devised for interferometric synthetic aperture microscopy are adapted to account for the diffraction-and defocusing-induced spatially varying THz beam width characteristic of narrow depth of focus, high-resolution confocal imaging. A frequency-swept two-dimensional TISAT confocal imaging instrument rapidly achieves in-focus, diffraction-limited resolution over a depth 12 times larger than the instrument's depth of focus in a manner that may be easily extended to three dimensions and greater depths. 相似文献
10.
衍射受限光学合成孔径成像系统像质评价 总被引:17,自引:6,他引:11
简述了光学合成孔径成像系统的原理,合成孔径成像系统在获得高截止频率的同时,降低了系统的中频性能,在空域表现为点扩展函数次峰增加。然后运用两点分辨率和光学传递函数对衍射受限光学合成孔径成像系统的像质评价问题进行了分析,指出了瑞利判据、斯派罗准则和“门限”判据的不足,认为当点扩展函数次峰大于主峰的0.5倍时,合成孔径系统与单孔径系统相比将失去优势。以光学传递函数为标准。分析三孔径合成系统子孔径尺寸、相互间距与等效系统孔径尺寸之间的关系。当子孔径直径不变时,随着其所在圆半径的增大,实际截止频率先增大,然后减小。 相似文献
11.
12.
星载极化相关型全极化微波辐射计是一种新型空间被动微波遥感仪器, 为海面风场等海洋大气环境参数的遥感探测提供了重要技术途径. 天线交叉极化校正是其数据预处理算法的重要环节. 本文针对星载极化相关型全极化微波辐射计天线交叉极化校正需求, 以极化相干检测理论为基础, 结合Stokes参数的定义, 自主推导了其适用的全极化天线温度方程. 该方程针对四个Stokes参数天线温度, 引入了Stokes参数之间交叉极化的振幅和相位, 并考虑了极化旋转角对天线方向图计算的影响. 最后, 建立了天线扫描波束与地球场景的几何对应关系, 对天线温度方程中各参数的确定方法进行了探讨. 全极化天线温度方程的建立为进一步开展星载极化相关型全极化微波辐射计天线交叉极化校正奠定了基础.
关键词:
全极化微波辐射计
天线交叉极化
天线温度方程
相干检测 相似文献
13.
Three-dimensional synthetic aperture integral imaging 总被引:3,自引:0,他引:3
We propose synthetic aperture integral imaging, in which an effectively enlarged aperture (or field of view) is obtained by movement of small integral imaging system. This system substantially increases the field of view and the viewing resolution. The feasibility of our approach is experimentally demonstrated. To the best of our knowledge, this is the first time the synthetic aperture technique has been applied to three-dimensional integral imaging. 相似文献
14.
一种机载合成孔径成像激光雷达聚束模式成像算法 总被引:10,自引:1,他引:9
合成孔径成像激光雷达是一种新的主动式有源的成像系统,可以获得比合成孔径雷达更高的分辨率,和更接近光学图片的效果.首先,在理想条件下分析了调频连续波的信号模型,推导出在连续波系统聚束模式下一种适用于机载合成孔径成像激光雷达系统的频率变标算法.然后,使用傅里叶变换法对符合von Karman谱的随机相位屏模拟大气湍流,并分析了Fried参量和合成孔径长度之间的关系.最后,仿真说明真空中采用方位预处理可以消除图像重影,并且补偿多普勒频移项可以消除8.6~9.3dB的能量损失和使图像散焦的现象.而在有大气影响时,合成孔径长度的选择小于Fried参量时,图像方位向可以良好聚焦. 相似文献
15.
A new method to improve the resolution of optical imaging systems beyond the classical Rayleigh resolution limit is presented. The technique relies on synthetic aperture generation in three stages. The first one (encoding stage) uses an illumination procedure that combines both on-axis and off-axis illumination beams with different polarization states onto the object. After the imaging system, a second stage (decoding stage) allows the recovering of the encoded spatial-frequency object information by means of an interferometric configuration based on the polarization coding carried out in the previous stage. Finally, a third stage (digital post-processing stage) is used to generate a synthetic aperture that is three times larger than the conventional aperture of the imaging system. The whole process allows us to obtain a superresolved image of the object. Experimental implementation of the approach for a commercial microscope objective is presented. 相似文献
16.
条带合成孔径成像自20世纪50年代提出,应用于雷达成像,并成功地应用于环境资源监测、灾害监测、海事管理及军事等领域。近年来,随着科学技术的发展,合成孔径成像日趋成熟,并扩展到其他领域,得到了广泛的应用。该文简要介绍了条带合成孔径成像的原理及其在雷达、声呐、无损检测及医学影像等方面的应用及发展。 相似文献
17.
V. A. Rassadovsky 《Radiophysics and Quantum Electronics》2007,50(10-11):877-884
We present the results of development of a method for eliminating the influence of an a priori unknown coefficient of reflection from the antenna — studied medium interface on accuracy of radiometric measurements of the medium temperature with the antenna contacting the medium. The method is based on modulation of receiver input noise and permits continuous automatic measurement of the reflection coefficient using the designed circuitry and algorithms for operating the radiometer and processing its output signal. Equations proving the efficiency of this method are obtained. The radiometer block diagram that realizes the proposed method is developed and a device for medical use is manufactured on its basis. Technical performance of the radiometer is given and test results of its measurement accuracy are presented. 相似文献
18.
J. Anthony Murphy Rachael Padman 《International Journal of Infrared and Millimeter Waves》1988,9(8):667-704
In this paper we consider the maximization of the throughput of a single large antenna, for two possible array configurations: focal plane imaging arrays and aperture plane phased arrays. We discuss trade-offs between the two types of array in terms of field of view, sampling efficiency and time to map, a source. We also discuss limits on the number of feed elements in an imaging array imposed by the deterioration in aperture efficiency off-axis. 相似文献
19.
20.
二维圆周光综合孔径阵的优化排列及其成像特性研究 总被引:4,自引:4,他引:4
光综合孔径成像的原理是应用干涉原理在空间频率域中进行采样,并通过傅里叶反变换或其他数值变换方法得到空间分辨力远高于单个孔径成像系统的目标图像。由若干个相同的小孔径在二维圆周上优化排列组成的综合孔径成像系统可以在二维空间频率域中实现较为均匀分布的、具有无冗余度的采样点覆盖,为高质量实时成像提供了一个有效的途径。运用模拟退火算法对由7~16个子孔径组成的二维圆周综合孔径阵列进行优化排列。并依据光学衍射成像原理,从空域和频域两个方面详细分析了二维圆周上优化排列与均匀排列光综合孔径阵的成像特性。对7~16个子孔径组成的光综合孔径的仿真结果表明:无论是在空域还是频域上,子孔径直径增大、孔径数目增多以及综合孔径阵的优化排列都是有利于提高成像质量的。但综合后的子孔径的直径的增大,虽然能获得极高的角分辨力,却并不利于成像质量的提高。 相似文献