共查询到18条相似文献,搜索用时 234 毫秒
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用CCD记录散斑场和参考光的干涉图样, 利用傅里叶变换法实现了散斑场复振幅以及相位分布的实验提取, 在复振幅实部零值线和虚部零值线切点处出现一种新的相位奇点, 与两条零值线交点处的传统相位奇点周围单调螺旋变化的相位分布不同, 绕切点一周的相位具有先增大后减小几乎呈对称性分布的特性, 为了解释这种新的相位奇点,提出了准孪生相位涡旋的概念. 在理论研究散斑场强度的纵向自相关函数的基础上, 实验观察散斑场相位涡旋的传播, 发现在光强纵向相关长度范围内的不同传播距离处的观察面上, 复振幅实部和虚部随机变化而涡旋的
关键词:
相位涡旋
散斑
干涉 相似文献
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全息干涉计量中干涉计量场的统计特性 总被引:1,自引:0,他引:1
本文运用统计学方法推导了全息干涉计量中散斑计量场的统计特性.证明了:干涉计量场的复振幅为复圆高斯随机变量;干扰计量场强度的概率密度服从负指数分布;散斑干涉计量场的系综平均值代表变形信息. 相似文献
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对超声入射至分布有细小凹坑的界平面,这一类弱散射界面背向散射所形成的超声散斑的一阶统计特性进行了研究.在假设条件下,理论分析的结果表明,空间超声散斑的振幅服从Rice分布,而它们的相位概率密度函数是一个包含Gauss分布函数和Gauss概率积分函数的复合函数.当细孔密度非常大时,超声散斑的振幅就趋于Rayleigh分布.应用作者建立的由计算机控制扫描的实验系统,对这一类弱散射界面反射超声散斑的振幅分布进行了测量.实验结果表明,理论分析的结果是正确的,由此,所作的假设条件也是成立的.
关键词:
弱散射
超声散斑
统计特性 相似文献
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在对4f光学成像系统中强散射体形成的像面散斑的统计特性的研究中, 首先通过散斑场光波复振幅的一般形式和双重指数函数近似求出散斑光强的系综平均, 然后利用散斑场光波复振幅的实部和虚部的旋转变换法求出散斑光强的方差, 最后得出了散斑对比度与随机表面统计参量和系统参量的直接表达式. 本结果与现有文献中包含随机表面相关面积或散射粒子数目的隐含表达式相比具有明显的改进, 并对标定随机表面的散斑对比度法具有重要意义.
关键词:
随机表面
像面散斑
对比度 相似文献
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用零相关相位板匀滑散斑的理论研究 总被引:1,自引:0,他引:1
对零相关相位板匀滑散斑的特性进行了理论分析和散值计算,结果表明尽管零相关相位板是针对入射场为平面波面而设计的,但在入射场的振幅和相位有一定起伏的情况下,其远场光斑的散斑对比度明显低于采用随机相位板的情形.因而用零盯关相位板匀滑散斑是一种更为有效的方法. 相似文献
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为了精确描述超声散斑场的特性,提出了采用计算机模拟产生超声散斑场的方法.利用模拟产生的高斯相关随机表面,获得了这类表面远场超声散斑场,同时得到了声强分布和相位分布.与实验产生的散斑场进行对比,建立了超声散斑场接收的实验系统,取与计算模拟相同的参数,获得了实验散斑场.通过对比发现:计算机模拟产生的超声散斑场相位存在奇异点,奇异点周围相位分布类似漩涡,计算机模拟产生的散斑场与实验得到的散斑场强度分布相似,强度值比实验产生的散斑场强度大,携带有用信息的高亮散斑较多,暗点较少,更利于研究和分析. 相似文献
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根据粗糙界面和大气湍流对传输激光束影响的相互统计独立性,给出了通过洁净大气湍流传输的椭圆高斯分布散斑场的非限制相位概率密度函数。 相似文献
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Some first-order statistics of speckle fields obeying the complex Gaussian probability density are investigated with the special emphasis on a possibility for the speckle contrast to exceed unity. It is shown that such enhanced fluctuations of speckle fields are generated when the probability density of the complex amplitude is non-circular with the vanishing mean. This means that Gaussian speckles having the contrast of unity are not necessarily fully developed speckles. Some practical situations producing such enhanced fluctuations in speckle fields are discussed. 相似文献
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M.A.C. Potenza M.D. Alaimo D. Pescini D. Magatti F. Ferri M. Giglio 《Optics and Lasers in Engineering》2006,44(7):722
We show that the time evolution of near-field scattering speckles, originated by a fluid suspension of particles, provides information about the velocity field in the fluid. This information can be extracted from a statistical analysis of speckle fields taken at different times, either by measuring their cross-correlation function or by recovering the power spectrum corresponding to the difference between the two speckle fields. Experimental data are in accordance to the expected behaviors. The results are independent of the scatterer's size, allowing one to exploit the technique also with sub-wavelength tracking particles. 相似文献
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Dynamic laser speckles and their application to velocity measurements of the diffuse object 总被引:3,自引:0,他引:3
In connection with the parameters of the optical configuration used to produce speckles and under illumination of a Gaussian
beam over a moving diffuse object, this paper discusses the statistical properties of dynamic speckles produced in the diffraction
and image fields by the diffuse object moving in a plane with constant velocity. Especially, the space-time correlation function
of the dynamic speckle intensity is examined in detail. Two typical speckle motions of translation and boiling are interpreted
for various optical configurations in the diffraction and image fields. As one of the interesting applications of dynamic
speckles to metrology, various methods for velocity measurements of the diffuse object are introduced. 相似文献
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CHENG Chuanfu SONG Hongsheng LIU Chunxiang REN Xiaorong ZHANG Ningyu TENG Shuyun & XU Zhizhan . Shanghai Institute of Optics Fine Mechanics Chinese Academy of Sciences P. O. Box - Shanghai China . Department of Physics Shandong Normal University Jinan China . Shandong Institute of Architecture Engineering Jinan China 《中国科学G辑(英文版)》2004,47(3):365-380
Speckle fields are the random light wave distributions produced when the light fields are scattered from random surfaces or a random medium. They appear in many optical phenomena that are related to light propagations[1,2] and have found wide appli-cations in a variety of scientific and technical fields. The examples of the recent impor-tant applications of speckles include the analysis of the movement of the granules[3], the three-dimensional imaging for the microstructures of metal nanocryst… 相似文献
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Weibull分布的雷达极化回波特征由三个分布参数来描述:波的强度、极化椭圆率角以及椭圆倾角.在瞬态极化理论的基础上,推导了三个分布参数的联合概率密度函数,标准Stokes矢量统计分布的联合概率密度函数及其边缘概率密度函数,并通过蒙塔卡罗方法进行了计算机仿真,结果验证了理论推导的正确性.Weibull分布随机极化电磁波瞬态极化统计特性的研究对高分辨条件下雷达目标的检测、识别和跟踪领域都有一定的理论指导意义.
关键词:
Weibull分布
极化椭圆参数
标准Stokes矢量
统计 相似文献
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Extremal properties of the statistics of speckle pattern are studied in the context of so-called “optically smoothed” light beams of laser-matter interaction. It is shown that the asymptotic statistics of the highest intensity in a speckle pattern, which can be associated with the most intense speckles, follows a Gumbel law, which is in agreement with numerical simulations. It is found that the probability density function of the most intense speckle peaks around the value corresponding to the logarithm of the number of speckles in the considered volume times the average intensity value of the speckle pattern. This result is of great interest for nonlinear processes, like instabilities, where extreme speckles play an important role. 相似文献