部分偏振激光散斑光强的统计特性

用液晶作为偏振调制器来改变光波的偏振度,形成部分偏振激光散斑图,进而研究部分偏振激光散斑光强的统计特性。     

像场散斑场相位差的统计性质

运用弱散射体产生的部分显现散斑场相位差自由标准偏差的近似表达式，分析了双会聚透镜组成的成像系统产生的部分显现高斯散斑场相位差的自由统计分布。     

ICE超声图像斑点噪声的统计分析

通过基于三次样条曲线的弹性图像配准方法对ICE(Intracardiac Echocardiographic)图像进行配准后提取对数斑点噪声并对其进行统计分析。该图像配准方法是使用基于斑点噪声统计特性的最大似然方法建立目标函数并进行最小化,然后再重构运动场函数并进而在所有像素点提取对数斑点噪声差异值。计算结果表明在图像不同区域噪声的统计特性呈现明显有区别的空间特征。     

非圆对称高斯分布激光散斑积分光强统计分布

由于某些应用中,如光学通信的误差概率计算,需要知道接收端光束强度起伏的概率分布。所以,目前对激光散斑积分光强起伏的统计分布规律的量子和经典理论的研究十分活跃,而激光大气闪烁统计分布方面的研究尤为活跃。然而,至今为止,这些研究工作皆局限于圆对称高斯分布大气散射场的闪烁分布并且忽略了接收检测有限孔径和时间累积效应。实际上,在气溶胶湍流大气(如雾、云)中传输的激光散斑的光场一般说来不再满足圆对称高斯分布。为了客观满足描述光束在实际大气中传输散斑积分光强起伏分布规律,十分必要研究描述云、雾大气中传输激光散斑光场的闪烁统计规律。本文将研究并给出非圆对称高斯分布散射场的积分光强起伏概率密度函数。     

参考束型散斑干涉计量中信息分布的统计模型

采用统计学方法建立了参考束型散斑干涉计量中信息分布的统计模型,由此导出了信息,的可测条件。     

多模光纤束斑纹场的某些特性

本文研究多模光纤束斑纹场经透镜后的光场特性以及两种有应用价值的斑纹场实验。     

Statistical properties of mobile-to-mobile land communicationchannels

Statistical properties of mobile-to-mobile land communication channels have been developed. In particular, the level-crossing rate and duration of fades of the envelope, the probability distribution of random FM, the expected number of crossings of the random phase and random FM of the channel, and the power spectrum of random FM of the channel have been considered     

高斯光束在对数型非线性介质中的传输特性

根据对数型非线性介质中高斯光束的束宽和波阵面曲率变化所满足的耦合方程,采用数值计算对高斯光束的传输特性进行了详细的分析。结合相图分析了高斯光束在不同初始条件下束宽与波阵面的变化情况。利用力学类比,讨论了高斯光束在传输过程中形成的对称呼吸模式与不对称呼吸模式的空间孤子。     

Statistical properties of Rayleigh backscattering in single-modefibers

An analytical model that takes into account the influence of the laser linewidth on Rayleigh backscattering is given. For an unmodulated source the power spectral density is found to be identical to the delayed self-homodyne spectrum of the laser. The backscattered signal was measured for different laser linewidths, and the results are compared with the theory. The effects of Rayleigh backscattering noise on fiber gyroscopes and bidirectional optical systems are discussed     

激光斑纹的衍射和斑纹强度的测量

介绍了激光斑纹衍射和斑纹强度测量实验.结果表明,当斑纹平均直径与测量孔直径之比d_r/d_0≥1时,可以观察到夫琅和费衍射图或“准”夫琅和费衍射圈.在d_r/d_0>>1时,可以得到负指数形式的几率密度函数,并且能用对比度来表征散射面的粗糙度.     

Statistical properties of coded interlaced and progressive imagesequences

We investigate the statistical properties of interlaced and progressive image sequences in order to determine what is the most efficient format from a coding point of view. Intra- and inter-coding modes are both considered. The main result is that, for both intra- and inter-images, the coding of progressive images outperforms the coding of interlaced ones for low bit rates and large motion vectors. Particular attention is paid to inter-coding with subpel accuracy, where the effects of nonideal interpolation filters and finite precision of the motion vector are taken into account.     

像面散斑平均尺寸对散斑干涉条纹图的影响

散斑计量中,为了在动态测量中得到清晰的原始散斑条纹图,使更有效的提取相位信息,提出一种改变像面散斑平均尺寸大小对散斑成像影响的方法,进而改善原始散斑条纹图的清晰度。通过分析光路参数F数和放大倍数与像面散斑尺寸大小的定量关系,通过实验进行了验证。实验结果表明,形变量一定,系统放大倍数为1,成像透镜F值为4.5,或者,当F数为2,系统放大倍数为3.5,像面散斑平均尺寸大小为5.841μm,最接近像面尺寸5.86μm成像效果最好,经正余弦算法滤波后,得到的散斑条纹图最清晰,证实了像面上散斑尺寸大小对散斑条纹图的影响。     

位置随机散斑相关测量方法及应用

本文提出了一种新的位置随机散斑相关测量方法.在新的方法中将数字图像分为若干个n×n像素的窗口,在每个窗口中确定一个或两个散斑点,散斑为高斯散斑.与原来的就整场取随机位置的方法相比较,制作出了散斑分布更均匀的局部位置随机的散斑图.本文还分析了基于局部随机位置点阵,利用成像透镜的低通滤波作用生成局部位置随机的散斑图的方法.文中分别模拟了局部位置随机散斑图和整场位置随机散斑图在数字散斑相关测量中的应用,将两种散斑相关测量的方法进行了比较分析.     

Statistical properties of local extrema in two-dimensional Gaussianrandom fields

This paper is concerned with the statistical properties of the local extrema and local maxima of two-dimensional (2D) Gaussian random fields (GRFs). A GRF may be represented by a linear filtering operation on a white noise field; the spatial properties of the GRF are then determined by the shape of the filter kernel function. New expressions are derived for the mean spatial density of local extrema and for the distribution of local extrema in a 2-D random field. The work is motivated by the problem of detecting known structures in images using 2D matched filters. The new results enable accurate performance predictions to be made of the reliability of such filters in the presence of noise. Case studies are presented for several well-known 2-D filter kernel functions     

Statistical properties of two sine waves in Gaussian noise

A detailed study is presented of some statistical properties of the stochastic process, that consists of the sum of two sine waves of unknown relative phase and a normal process. Since none of the statistics investigated seem to yield a closed-form expression, all the derivations are cast in a form that is particularly suitable for machine computation. Specifically, results are presented for the probability density function (pdf) of the envelope and the instantaneous value, the moments of these distributions, and the relative cumulative density function (cdf). The analysis hinges on expanding the functions of interest in a way that allows computation by means of recursive relations. Specifically, all the expansions are expressed in terms of sums of products of Gaussian hypergeometric functions and Laguerre polynomials. Computer results obtained on a CDC 6600 are presented. Ifaandbare the amplitudes of the two sine waves, normalized to the rms noise level, the expansions presented are useful up to values ofa,bof about 17 dB, in double precision on the CDC 6600. A different approximation is also given for the case of very high SNR.     

Statistical properties of amplify and forward relay fading channels

Cooperation diversity schemes have been proposed for cellular networks that permit mobile stations to relay signals to a final destination, thereby increasing the network capacity and coverage. The mobile relays either decode and retransmit the received signal or simply amplify and forward (A & F) the signal. The overall channel from the source to the destination via the relay in A & F systems is "double" Gaussian with properties quite different from a typical cellular channel. Since very little is known about A & F relay fading channels, this paper considers their statistical properties such as the envelope probability density function, autocorrelation, level crossing rate, and system performance characteristics like frequency of outages and average outage durations. We briefly discuss the simulation of these channels and verify our analysis by simulations.     

Statistical properties of out-of-frame detection schemes fordigital transmission systems

The importance of the misframe times for DS1 frame synchronization has often been addressed in designing and using network elements and mediation units. By extending the work of J. H. Eu and W. W. Rollins (1991), Markov chain first passage time analysis is used to derive higher moments of the misframe times in both random and burst error environments. This methodology is of great value in evaluating frame synchronization techniques for digital transmission systems. By experimenting with several out-of-frame detection schemes and reasonable values for bit error ratio (BER), it is shown that misframe times are always approximately exponentially distributed for all schemes     

Statistical properties of stimulated Raman crosstalk in WDM systems

The crosstalk variance of stimulated Raman crosstalk in wavelength-division-multiplexing (WDM) systems is derived analytically in a closed-form formula for all systems with different walkoff length. The probability density function (pdf) of stimulated Raman crosstalk is found to be lognormal distribution (Gaussian distribution in decibel scale). Both power penalty and power limit induced by Raman crosstalk are evaluated and can be applied to single- and multispan WDM systems