共查询到20条相似文献,搜索用时 31 毫秒
1.
A theoretical and experimental analysis is carried out showing the effect of multiple exposures on fringes in the case of three-dimensional motion of a diffuse object illuminated by a diverging beam from a laser point source. Experimental conditions are such that the speckle patterns remain fully correlated in spite of the object moving in three-dimensional space in a direction that makes an angle with the optical axis. Owing to the in-plane component of the three-dimensional displacement the point of null-speckle displacement shifts either in the direction of the in-plane component of the motion or in the opposite direction depending upon the direction of the out-of-plane displacement component. This modifies the fringe profile as compared with the case of pure out-of-plane motion. The intensity distribution at the Fresnel plane of a specklegram is investigated after filtering by a converging beam for double exposure and multiple exposures. Good agreement is found between the theoretical and experimental results. 相似文献
2.
Layer boundaries detection with LIDAR is of great significance for the meteorological and environmental research. Apart from the background noise, multiple scattering can also seriously affect the detection results in LIDAR signal processing. To alleviate these issues, a novel approach was proposed based upon morphological filtering and multiple scattering correction with multiple iterations, which essentially acts as a weighted algorithm with multiple scattering factors in different filtering scales, and applies integral extinction coefficients as media to perform correction. Simulations on artificial signals and real LIDAR signals support this approach. 相似文献
3.
Two images of a rough curved object, illuminated by a coherent parallel beam are recorded on the same photographic plate. The incident beam is slightly tilted between the two exposures. In a suitable filtering set-up we observe the depth contours of the object (parallel to the photographic plate); the experimental limitations are discussed. 相似文献
4.
The filtering characteristics of multiple ring resonator (MRR) filters are modeled and investigated. The ring resonators of the MRR have identical perimeters and the coupling coefficients distribution provide passband characteristics with steeper roll-off, flatter top and greater stopband rejection than single ring resonator. The theoretical results are indicated that the optical loss in micro-rings has a strong influence on the characteristics of the MRR filters. A novel attempt has been made to employ a graphical approach in the analytical derivation of the optical transfer functions of MRR filters that can be represented in signal flow graph diagrams. 相似文献
5.
One-dimensional photonic crystal structures for multiple channeled
filtering and polarization selective filtering in the terahertz
(THz) range are studied theoretically. The design of aperiodic photonic
quantum-well (APQW) structures for multiple channeled filtering and
different polarization filtering at arbitrary preassigned
frequencies are achieved by using the simulated annealing algorithm
with a special merit function. The parameters of these filters can
be expediently controlled and the transmission characters are
polarization dependent. Numerical simulations show that the designed
APQWs can meet the desired specification well. 相似文献
6.
分析提取宽带电火花声源信号,受到船舶辐射噪声的严重干扰,在5 kHz以下的能量集中区信噪比低,且二者Lipschitz指数特性相近,传统基于相邻尺度相关的滤波算法抗干扰能力有限。根据宽带电火花声源信号不同频带所受干扰的不同,信噪比较高的小尺度高频小波系数,采用相邻尺度相关的滤波算法;信噪比较低的大尺度中低频小波系数,采用跨尺度相关的滤波算法,并对算法中阈值系数的选取方法进行修正。结果表明,该算法滤波效果良好,有效的提取了电火花声源信号,适合窄带强干扰背景噪声下的宽带水声信号处理。 相似文献
7.
Quantum routing in a T-bulge-shaped waveguide system coupled with a driven cyclic three-level atom and a twolevel atom is investigated theoretically.By employing the discrete-coordinate scattering method,exact expressions of the transport coefficients along three ports of the waveguide channels are derived.Our results show that bidirectional high transfer-rate single-photon routing between two channels can be effectively implemented,with the help of the effective potential generated by two atoms and the external driving.Moreover,multiple band zero-transmission emerges in the scattering spectra,arising from the quantum interferences among photons scattered by the boundary and the bulged resonators.The proposed system may suggest an efficient duplex router with filtering functions. 相似文献
8.
双折射滤波片的优化参量 总被引:2,自引:0,他引:2
研究了双折射滤波片的滤波和调谐性质。利用矩阵方法和反射、透射系数,给出了波片两个界面的菲涅耳系数。利用相移公式和光线轨迹公式,由入射角和光轴方位角可计算波片精确的相移公式。将上述系数和这一波片的相移公式用于琼斯矩阵,得到透射率的本征矩阵。该矩阵的本征值即为波片的透射系数。由此,给出了波片的主要性质(特别是透射宽度),讨论了波片参量(入射角、方位角和厚度)对波片性质的影响。利用相移公式,讨论了波片的调谐性质,并给出了选择参量的最佳范围。对石英波片,最佳参量为:厚度约在1500~2000μm,方位角大于45°,循环系数r尽可能大。在激光器增益较大时,选择较小的入射角。 相似文献
9.
适当均衡耳机到鼓膜的传递函数可有效提高耳机声重放效果。耳廓与耳道滤波效应引起的幅度峰谷有助于人耳听觉感知,以平直幅频响应为目标的幅度均衡无法保持适当的峰谷。该文提出了基于roex滤波器与Mel频率倒谱系数的耳机到鼓膜的传递函数平滑方法,用于模拟人耳听觉感知特性和平滑耳机到鼓膜的传递函数,使均衡后的幅频响应保持相应的峰谷,避免了幅度峰谷过渡均衡。实验结果表明,进行耳机到鼓膜的传递函数平滑的幅度均衡对提高耳机的音色有显著作用,基于Mel频率倒谱系数平滑的幅度均衡对提高耳机的音色最为显著。 相似文献
10.
基于数学形态学和遗传优化的图像去噪 总被引:4,自引:0,他引:4
针对图像滤波时损失图像细节这一问题,提出了一种自适应多尺度形态滤波方法,在普通多尺度形态开、闭滤波基础上增加了多尺度top hat变换和bottom hat变换,用于提取并平滑小尺度的图像信息。top hat变换和bottom hat变换的系数对整个滤波器性能起着重要的作用,采用遗传优化的方法对其进行优化。实验结果表明,该方法噪声去除效果好,图像细节保持完整,提高了输出图像的信噪比,增强了滤波器的自适应性和智能性,处理效果明显优于传统滤波方法。 相似文献
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基于小波阈值理论的光学图像去云处理新算法 总被引:3,自引:0,他引:3
分析了部分云覆盖的单幅光学遥感图像经过多层小波变换后,景物信息和云噪音在小波分解系数中的分布关系,并提出了云区阈值法来有效去除云噪音.通过选择适当的分界层数,将景物信息、云噪音尽可能分别分配到低层和高层细节系数中.高层细节系数中除主要包含云噪音外,也有部分有用景物信息.由于云噪音亮度大于景物,根据亮度特征合理选择高层细节系数的亮度阈值,去除云噪音,而保留其中的景物信息.通过对低层、高层细节系数和近似系数分别设置权重,增加景物对比度,减小残留云影响,从而重构得到恢复图像.提出了以信息熵作为分界层数、权重、阈值等参量选择的定量标准.实验证明,按信息熵标准能正确地选择参量,依据本文算法得到的去云效果远优越于同态滤波和Retinex算法,且能充分保留云区以外景物信息. 相似文献
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14.
M.P. Arroyo T. Yonte M. Quintanilla J.M. Saviron 《Optics and Lasers in Engineering》1988,9(3-4):295-316
We present here an application of particle image velocimetry (PIV) to the analysis of the Rayleigh-Be´nard convection patterns in small ☐es, in which a low power laser (5 mW He-Ne) has been used and photographs with a high number of exposures have been taken. Parameters which affect the quality of photographs are analyzed and related with the number of exposures.
The data reduction is made by fringe analysis (point-by-point technique) and by spatial filtering (whole-field technique). The fringe analysis is made with a1 − D integration method, which has been fully automated in the way described here.
The velocity field is numerically processed in order to obtain some additional information (like flow rates, vorticity, streamlines, …) which is relevant in fluid mechanics.
Finally, results obtained from an application of the whole process to the study of motion in the mid-plane of a Rayleigh-Be´nard cell are shown. 相似文献
15.
H. I. Nurdin 《Russian Journal of Mathematical Physics》2014,21(3):386-398
In this paper, we treat the quantum filtering problem for multiple input multiple output (MIMO) Markovian open quantum systems coupled to multiple boson fields in an arbitrary zero-mean jointly Gaussian state, using the reference probability approach formulated by Bouten and van Handel as a quantum version of a well-known method of the same name from classical nonlinear filtering theory, and exploiting the generalized Araki-Woods representation of Gough. This includes Gaussian field states such as vacuum, squeezed vacuum, thermal, and squeezed thermal states as special cases. The contribution is a derivation of the general quantum filtering equation (or stochastic master equation as they are known in the quantum optics community) in the full MIMO setup for any zero-mean jointly Gaussian input field states, up to some mild rank assumptions on certain matrices relating to the measurement vector. 相似文献
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强度调制偏振光谱仪解调系数参考光测量方法 总被引:5,自引:1,他引:4
针对由理论计算得到的解调系数无法实现强度调制偏振光谱仪实验系统(以下简称"实验系统")测量数据解调处理的问题,提出了测量参考光获取实验系统解调系数的解决方法。该方法通过测量已知偏振态参考光经过实验系统调制器后输出的强度谱,结合傅里叶变换、滤波和逆傅里叶变换等数字信号处理过程,可从测量结果中分离出实验系统的真实解调系数。分析了该方法的理论依据,给出了实验系统解调系数的实测结果,并利用得到的解调系数,对实验系统测量典型待测光源(近似自然光和完全线偏振光)的测量数据进行了解调处理。解调处理结果显示:在有效测量波段范围内(550~650nm),以卤钨灯为光源的平行光管直接输出光的偏振度值约为10%;经过线偏振器起偏后,其偏振度值接近100%,与实际分析结果完全相符。验证了强度调制系统解调系数参考光测量方法的可行性。 相似文献
18.
We theoretically investigate an optical system, which consists of a waveguide side-coupled to a cascade of cavities, the filtering properties by the time domain coupled-mode theory. In such a system, the filter operating bandwidth and the width of transmission peaks are completely determined by the mutual coupling coefficients between the cavities. The characteristics are numerically demonstrated in photonic crystals by the finite-difference time-domain method. 相似文献
19.
Suzhen Yuan Yongle Lu Xuefeng Mao Yuan Luo Jianguo Yuan 《International Journal of Theoretical Physics》2018,57(3):804-813
We investigate the quantum image filtering in spatial domain proposed by Yuan et al. (Int. J. Theor. Phys. 56(8), 2495–2511, 2017). Although the complexity of this algorithm is much better than the classical exhaustive algorithm, there may be a defect in it: the quantum multiplication was replaced by quantum addition. There are two shortcomings: 1) We should know exactly the value of the filter coefficients before each filtering behavior. 2) This method is only suitable for integer filter coefficients but not for decimal filter coefficients. In this paper, an improved version is proposed which takes full advantage of the quantum multiplication and can overcome these two shortcomings. The theoretical analysis indicates that the time complexity is the same as the previous algorithm. So this algorithm is also efficient. 相似文献
20.
刘伟宁 《中国光学与应用光学文摘》2011,(5)
分析了基于小波变换进行弱小目标检测的基本思想,利用小波变换的多尺度多分辨率特性,结合小波变换系数的方向特性和扩散滤波扩散方向的可选择性,提出了基于小波域扩散滤波的弱小目标检测算法。采用该算法对不同尺度、不同方向的小波系数分别进行扩散滤波,取得了较好的效果。仿真试验结果表明:该算法能在Gaussian噪声背景和不均匀背景下实现对对比度为2%的微弱目标的检测。 相似文献