共查询到20条相似文献,搜索用时 23 毫秒
1.
The coherent-mode representation theory is firstly used to analyze lensless two-color ghost imaging. A quite complicated expression about the point-spread function(PSF) needs to be given to analyze which wavelength has a stronger affect on imaging quality when the usual integral representation theory is used to ghost imaging. Unlike this theory, the coherent-mode representation theory shows that imaging quality depends crucially on the distribution of the decomposition coefficients of the object imaged in a two-color ghost imaging. The analytical expression of the decomposition coefficients of the object is unconcerned with the wavelength of the light used in the reference arm, but has relevance with the wavelength in the object arm. In other words, imaging quality of two-color ghost imaging depends primarily on the wavelength of the light illuminating the object. Our simulation results also demonstrate this conclusion. 相似文献
2.
3.
Theory of the coherent-mode decomposition of laser beams is proposed. The new model for the flat-topped beams proposed by Li recently is taken as an example. The analytical expressions for the M^2-factor and mode coherence coefficients of flat-topped beams have been derived in the rectangular coordinate system, by means of which the mode correlation, mode structure, and coherent-mode decomposition of flat-topped beams can be analysed. 相似文献
4.
The equation for free-space propagation of the generalized radiance defined formerly by the authors in terms of the coherent-mode representation of the cross-spectral density function is derived within the accuracy of the paraxial approximation. It is shown that, in the short-wavelength limit, this generalized radiance obeys in a good approximation the fundamental radiative transfer law of classical radiometry. 相似文献
5.
6.
A new method for calculating image intensity distribution in partially coherent illumination is described. The method is based on the coherent-mode representation of the cross-spectral density function of illumination field and allows considerable reduction of the computational effort needed for image intensity calculation in comparison with the direct method. The computational efficiency of the method is larger the more coherent is the illumination in a global sense. An example of calculating image intensity for Schell-model illumination is compared with theoretical results. 相似文献
7.
针对常规诊断方法对螺栓的连接状态识别效果差、鲁棒性和抗噪性弱等问题,提出了基于深度学习理论的螺栓检测新方法。首先以4种预紧力状态下的法兰螺栓结构产生的声发射信号为研究对象,借助于自适应噪声的完整集成经验模态分解理论以及梅尔频率倒谱系数特征提取方式,实现了声发射信号的自适应消噪和最优模态函数分量组的选取,提取到了可以较好分辨螺栓连接状态的梅尔频率倒谱系数特征值。通过训练模型,较好地对4种连接状态下的螺栓进行了识别。结果表明,该模型在法兰螺栓的声发射信号的诊断中,准确率高,具有较好的抗噪性和鲁棒性。 相似文献
8.
Kisik Kim 《Optics Communications》2006,261(1):19-22
A very useful theoretical tool for investigating coherence properties of stochastic scalar sources and stochastic scalar fields is the so-called coherent-mode representation. We introduce a somewhat similar new representation for planar, secondary stochastic electromag netic sources which generate beams. It consists of three expansions for the three independent elements of the 2 × 2 electric cross-spectral density matrix of the beam. The expansion of the diagonal elements of the matrix are coherent-mode representations in the sense of the scalar theory. The third one, for each off-diagonal element, is a bi-modal expansion, expressed in terms of the coherent modes of the diagonal elements. 相似文献
9.
The visibility of ghost-interference patterns is investigated firstly based on the coherent-mode representation theory. We find that the intensity correlation function can be changed from the usually two-dimensional integral representation to a new one-dimensional summation representation. During the process of analyzing the effects from the light source's properties and the transmission area of the object imaged on the imaging visibility, it is shown that by compared with the results from the integral representation, the coherent mode representation is quite useful to understand more clearly the whole process of correlated imaging. 相似文献
10.
LIANG Xian-Ting 《理论物理通讯》2003,39(5):537-542
By using the Holevo-Schumacher-Westmoreland theorem and through solving eigenvalues of states out from the quantum noisy channels directly, or with the help of the Bloch sphere representation, or Stokes parametrization representation, we investigate the classical information capacities of some well-known quantum noisy channels. 相似文献
11.
12.
针对含噪图像增强问题,提出一种基于小波域三状态隐马尔可夫树模型的方法,采用三状态的高斯混合模型逼近小波系数的分布,不需要设定精确的阈值,依据期望最大算法训练得到的每个系数所属状态的后验概率,将系数区分为噪声系数、弱边缘系数和强边缘系数,然后通过抑制噪声系数,增强细节特征系数来达到对含噪图像增强的目的,并引入循环平移策略避免人工失真.通过对含噪的标准图像和人脑核磁共振图像进行仿真实验,并与几种经典的图像增强方法作视觉上的对比和定量分析.实验结果表明,本文所提出的方法具有很好的鲁棒性,在突出了图像中更多的细节信息的同时,可以有效抑制噪声. 相似文献
13.
On a spin quaternionic-Kähler manifold M4m, we give the spectral decomposition of the spin bundle the action of the fundamental 4-form Ω. Moreover, we compute the eigenvalues of Ω which, in the compact case, play an essential role in the problem of estimating the eigenvalues of the Dirac operator. The proof is based on the decomposition of the spin representation into irreducible components under the action of the group Sp(1) × Sp(m). We show that this algebraic results induces a Whitney decomposition of the spin bundle which, when restricted to the fibres, is the spectral decomposition under the action of Ω. 相似文献
14.
提出一种用非冗余轮廓波的中低比特率图像质量可伸缩编码算法。该算法采用双正交小波分解和方向滤波器组(DFB)实现图像的非冗余稀疏表示, 不但具有轮廓波对图像中线状奇异性边缘和纹理细节的稀疏表示特点, 而且克服了轮廓波变换系数4/3冗余的缺点。算法中对图像非冗余轮廓波系数各子带系数分布进行统计分析, 通过对变换系数的重新组合, 构造了有利于图像编码的空间方向树结构, 并统计验证了其零树特性, 采用分级树集合分裂和阈值量化达到图像质量可伸缩的嵌入式编码。实验结果表明,其解码算法在中低比特率压缩情况下, 压缩后重构图像的感知质量明显优于小波域SPIHT,JPEG2000编码标准, 峰值信噪比PSNR值与JPEG2000相当, 而图像纹理和边缘细节的视觉效果优于JPEG2000和小波域SPIHT算法。 相似文献
15.
根据电荷通过低温量子导体时具有的二项分布导致散粒噪声这一结论,结合Landauer电流公式的物理内涵建立了相干介观系统中的散粒噪声模型,并通过Monte Carlo模拟方法产生了散粒噪声时间序列.介观系统中散粒噪声的抑制来源于电子输运时的相关性,传输本征值双峰分布导致量子混沌腔和无序金属中的散粒噪声抑制.根据这两个结论,通过Monte Carlo模拟定性地分析了传输本征值分布与电子输运相关性之间的关系.
关键词:
散粒噪声
Landauer公式
介观系统 相似文献
16.
A noise reduction method based on weighted manifold decomposition is proposed in this paper, which does not need knowledge of the chaotic dynamics and choosing number of eigenvalues.The simulation indicates that the performance of this method can increase the signal-to-noise ratio of noisy chaotic time series. 相似文献
17.
18.
Orbital angular momentum of the coherent beam has been intensively studied and promises potential applications in free space optical communication. But the orbital angular momentum of partially coherent beam is not well known. In this communication the coherent-mode representation method is adopted to describe the partially coherent beam and the orbital angular momentum spectrum is introduced for the partially coherent beam. The characteristics of the orbital angular momentum spectrum of partially coherent beam are discussed. To study the influence of the partial coherence on the optical link, the channel capacity is studied, with two kinds of available mode separators included. 相似文献
19.
Piotr Śniady 《Communications in Mathematical Physics》2000,211(3):615-628
We discuss the meaning of renormalization used for deriving quadratic bosonic commutation relations introduced by Accardi
[ALV] and find a representation of these relations on an interacting Fock space. Also, we investigate classical stochastic
processes which can be constructed from noncommutative quadratic white noise. We postulate quadratic free white noise commutation
relations and find their representation on an interacting Fock space.
Received: 23 August 1999 / Accepted: 8 December 1999 相似文献