共查询到20条相似文献,搜索用时 343 毫秒
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讨论n平面线性相干光处理系统(简称n平面线性系统)的一般性质。在两个特例情况下,借助于傅里叶变换的相似性定理和空间频率的标度变换,可以证明:n平面线性系统的(n—1)个间距参数{zi}n-1不是实质性参数。利用所得结果,演示了相干光成象和空域中的频率的标度变换,说明理论结果是有效的。
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用成象自由度评价光学系统的信息量 总被引:1,自引:1,他引:0
本文探讨了一般光学系统的成象自由度传递及信息量问题,计算了不同信噪比σ0/σn下一维相干光和非相干光照明的衍射受限系统的有效自由度数Noff,并与经典分辨率理论的象素数作了比较。 相似文献
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空间频率彩色编码的方法是基于傅里叶光学中的空间滤波技术.关于相干光照明下的空间滤波方法在图象处理上的应用已为大家所熟知[1].这种方法对图象增强有明显作用,其主要缺点是:(1)由于用激光作光源,往往带来难以避免的相干噪声,严重地影响了成象质量.(2)无论用哪种滤波器,在突出某部分信息的同时,往往丢失了其他信息,故处理后的图象有时失去了原图的形象.空间频率彩色编码避免了上述缺点. 一、空间频率彩色编码方法及其发展 此方法所用光路基本上和相干光4f系统类似,只是用产生白光的溴钨灯S及一小孔W作为点光源,以代替激光.光经透镜L0准… 相似文献
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穆斯堡尔成象技术是1987 年由美国国家标准局S.J.Norton首先提出的[1].它与X射线成象(又称为CT断层成象)、核磁共振成象(NMR)一样能给出立体图象,虽然现在还不能在医学中应用,但在材料科学研究方面却已显示出广泛的应用前景. 在介绍穆斯堡尔成象之前,先介绍一下NMR成象.由于穆斯堡尔成象与NMR成象都依赖于原子核共振效应,因此它们具有许多相同的特征.NMR成象的原理是:由于原子核共振频率正比于局域磁场强度,因此,当施加一个外磁场于自旋体系时,不同频率的信号对应于实验样品内不同的空间位置.用这种方法可以将不同频率的信号转变为… 相似文献
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部分相干光在大气湍流中水平传输路径上的展宽与漂移 总被引:1,自引:0,他引:1
基于部分相干高斯谢尔模型(GSM)光束在强湍流中的光束扩展半径,利用Andrews和Philips经典漂移方差模型推导了部分相干光在中强弱大气湍流中水平传输的漂移方差表达式,讨论了部分相干光在中、强、弱大气湍流中的展宽和漂移特性。结果表明:部分相干光的光束扩展受湍流的影响比受完全相干光的影响要小,初始半径越小的光束受到湍流的影响越大。短距离传输时,不同波长引起的光束漂移差别很小,且随着初始光束半径的增大这种差别随之减小。传输距离大于2km时,中强湍流中光束漂移均与波长有关且强湍流区漂移量较为明显。传输距离在10km内,光束空间相干长度大于0.005m时,光源空间相干长度对漂移的影响很小。 相似文献
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We describe a method of obtaining optical sectioning with a standard wide-field fluorescence microscope. The method involves acquiring two images, one with nonuniform illumination (in our case, speckle) and another with uniform illumination (in our case, randomized speckle). An evaluation of the local contrast in the speckle-illumination image provides an optically sectioned image with low resolution. This is complemented with high-resolution information obtained from the uniform-illumination image. A fusion of both images leads to a full resolution image that is optically sectioned across all spatial frequencies. This hybrid illumination method is fast, robust, and generalizable to a variety of illumination and imaging configurations. 相似文献
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Jang C. Choi K. C. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》2010,38(2):106-112
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In the case that the image reconstructed from a cylindrical holographic stereogram with laser light reconstruction (LCHS) is observed by binocular vision, the 3-D distortion characteristics of the image are studied. Using an object of a distinctive construction, some examples are calculated and experimental results are also shown, and the optimum condition to synthesize the LCHS is given. 相似文献
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B. V. Krissinel S. M. Kuznetsova A. G. Obukhov G. Ya. Smol'kov 《Radiophysics and Quantum Electronics》1996,39(11-12):990-994
This paper is devoted to the problem of solar image recovery in synthesizing radio brightness maps in the case of an incomplete filling of the spectral region (the Fourier data are bounded by a cone with an angle much smaller than 180 deg.) The image was recovered by the method of projection onto closed convex sets (PCCS). Brief theoretical postulates which formed the basis for this method are presented. A comparative characteristic with the CLEAN method is given. The results of using this method for the model data and real data (recovery of the solar radio image obtained in the knife-edge beams of the SSRT) are presented. 相似文献
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Xu SH Keeffe M Yang Y Chen C Yu M Lapeyre GJ Rotenberg E Denlinger J Yates JT 《Physical review letters》2000,84(5):939-942
A new adsorption site for adsorbed acetylene on Si(100) is observed by photoelectron imaging based on the holographic principle. The diffraction effects in the carbon 1s angle-resolved photoemission are inverted (including the small-cone method) to obtain an image of the atom's neighboring carbon. The chemisorbed acetylene molecule is bonded to four silicon surface atoms. In contrast to the C2H2 case, the image for adsorbed C2H4 shows it bonded to two Si surface atoms. 相似文献
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The radiation emitted by a time-harmonic elementary current in magnetized electron plasma half-space, bounded by an ideal electric plane, is investigated using an exact formulation. It is found that: conventional image principle holds for vertical magnetization case; while for parallel magnetization case, coupled image principle seems to be valid. 相似文献
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Amit Aran Naveen K. Nishchal Vinod K. Beri Arun K. Gupta 《Optics and Lasers in Engineering》2008,46(1):34-41
In this paper, we report a log-polar transform-based filter for in-plane rotation and scale-invariant target recognition. The log-polar transform is a known space-invariant image representation used in several image vision systems to eliminate the effects of scale and rotation in an image. In case of in-plane rotation invariance, peaks shift horizontally, while in case of scale invariance, peaks shift vertically. For full out-of-plane rotation-invariance (0–360°), log-polar transformed images are used to train the wavelet-modified maximum average correlation height (WaveMACH) filter. Correlation peak height and peak-to-sidelobe ratio have been calculated as metrics of goodness of the log-polar transform-based WaveMACH filter. This filter would reduce the memory requirement for filter storage in a practical system. Simulation results have been presented. 相似文献