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1.
The six-term developments of the far-field amplitude and the transmission coefficient formerly given for the high-frequency diffraction of a plane sound wave by a circular aperture in an infinite plane sound-soft screen at normal incidence are corrected and numerically evaluated. 相似文献
2.
Werner Braunbek 《Zeitschrift für Physik A Hadrons and Nuclei》1959,156(1):66-77
By means of an approximate method formerly published by this author, diffraction by an aperture in a screen, which is not plane, is discussed. For the special case of a circular aperture in a funnel-shaped screen, the diffraction field on the axis behind the screen is computed for an incident scalar plane wave (different boundary conditions) and for an incident electromagnetic plane wave propagating in the direction of the axis. 相似文献
3.
Jaroslav Pachner 《Czechoslovak Journal of Physics》1956,6(1):8-11
The problem of the diffraction of an arbitrarily polarized electromagnetic plane wave by a perfectly conducting plane screen of infinitesimal thickness is reduced to scalar problems by the method known from earlier papers. The wave field diffracted either by a screen of infinite extent which is perforated by an aperture of arbitrary size and shape or by a complementary screen is then described by means of the bra-vectors, ket-vectors and linear operators introduced by the present author in one of his preceding papers. 相似文献
4.
弱散射屏产生的远场散斑由一个中央亮斑和一个分布于亮斑周围而与正态散斑类似的散斑结构, 根据弱散射屏远场的散斑图样, 人们假设弱散射屏产生的像面散斑为均匀背景与正态散斑两者相干叠加的结果, 但这种假设与实际像面散斑存在歧异, 基于上述情况, 本文利用4f高通滤波光学成像系统, 研究了高斯型弱散射屏产生的像面散斑场的统计特性, 得出只有表面均方根粗糙度与入射光波的波长相差不多时上述假设才是可行的结论.
关键词:
弱散射屏
f光学成像系统')" href="#">4f光学成像系统
像面散斑 相似文献
5.
The field distribution and the spectrum of plasma eigenmodes are determined for a circular hole in a screen having the form of a hyperboloid of revolution. The spectrum of plasmons is obtained for a planar screen with a circular hole. The symmetric mode with m=1 can be excited in the field of a dipole oriented along the screen plane, whereas the antisymmetric mode with m=0 can be excited by a dipole perpendicular to the screen plane. 相似文献
6.
Based on the plane wave analysis and the superposition of the plane waves, the diffraction of a Gaussian beam by a periodic screen with a dielectric plate is analyzed. The reflection power coefficient for different parameters of the beam and the screen is given. When the beam waist size is increased the results reaches that of the plane wave. It has been found that the power reflection coefficient is not sensitive to the beam waist size, however, it is sensitive to the period of the grating and polarization angle. 相似文献
7.
本文在文献[8]的基础上,提出了一个平面屏系统中标量光波传播的矩阵理论。由于采用的是柱坐标系,所以它主要适宜于具有理想轴对称性的系统。它的主要优点,是较便于处理上述系统中某些用已有理论实际上较难处理的光传播问题。本文中未考虑散射屏。这个理论的适用范围是:系统中所有平面屏都垂直光传播轴;可对每一屏的衍射应用本文的衍射公式和近似条件;在反射、吸收和增益屏上的入射光锥角较小等。作为应用的例子,本文得出和讨论了无源光学谐振腔中振荡模的矩阵方程。把它和已有的Fox和Li的积分方程作了比较,表明了矩阵方程具有某些重要的实际优点。
关键词: 相似文献
8.
Tractable analytic expressions are developed for a variety of basic statistical quantities involving a Gaussian-beam wave propagating through a random medium confined to a portion of the propagation path between input and output planes, the limiting case of which defines a thin random phase screen. For a plane wave incident on a phase screen located midway between input and output planes, it is well known that the statistics in the receiver plane are in close agreement with those associated with a plane wave propagating through an extended random medium between input and output planes. For a similar comparison between a phase screen and extended turbulence in the case of a Gaussian-beam wave at the input plane, the present analysis reveals that the phase screen must be positioned between input and output planes differently from the plane-wave case, the position being dependent upon the Fresnel ratio of the Gaussian beam. The analytic results developed in this paper for the thin phase screen model are based on the Kolmogorov power-law spectrum for refractive-index fluctuations and the Rytov approximation. Extension of these results to multiple phase screens is also discussed. 相似文献
9.
Eldar Musa 《Optics and Lasers in Engineering》2011,49(3):313-317
In this paper, a line-laser-based yarn break sensor is proposed. In the proposed sensor, yarns are illuminated by a line laser placed on one side of the yarn plane. A screen is placed on the other side and the image formed on the screen is detected by a camera. The total number of yarns is compared with the total number of shadows formed by the yarns or the total number of light spots formed due to the distances between yarns. If the total number of yarns to be detected is greater than the total number of shadows or light spots formed due to the distances between the yarns, the sensor warns of breaking. In the proposed method, evaluation is made using only light spots or shadows formed by the yarns. Consequently, the yarn type, structure, color, or dimensions do not affect the results.Design principles of the line-laser-based yarn break sensor, which consists of a screen and a Charged Coupled Device (CCD) camera, are presented. The screen displays the shadows formed by the yarns and the light spots formed due to the distances between them. The CCD camera detects the image on the screen. Formation of the shadows by the yarns is explained and an analytical formula that expresses the dimensions of the shadows is obtained. The detection area of the sensor is expressed relative to the total number of yarns, yarn thickness, and distances between the yarns. Line laser radiation angle and light spot intensity equations are obtained relative to the width of the detection area and the height of the line laser placement. The screen length is obtained relative to the number of yarns and the placement of the laser, the yarn plane, and the screen.Different placement situations of the line laser (transmitter), the screen, and the CCD camera (receiver) relative to the yarn plane are discussed. An experimental setup is developed to test the system. The image formed on the screen is studied. 相似文献
10.
Yijun He Quanrang Yang 《International Journal of Infrared and Millimeter Waves》1993,14(11):2371-2378
A uniform high-frequency solution is presented for the diffraction by a dielectric spherical mirror by a Gauss beam. Using the complex source-point theory, the radial field of quasi-optical power combiner is obtained. The E or H plane patterns of the combiner are calculated. 相似文献
11.
Scattering of a plane wave (X-ray) by a plane parallel slab with perfect grating is treated by means of an integral equation. The formulas obtained include the cases of grazing incidence and grazing excidence which had to be excluded in the usual theory. 相似文献
12.
Role of spectral cues in median plane localization 总被引:6,自引:0,他引:6
The role of spectral cues in the sound source to ear transfer function in median plane sound localization is investigated in this paper. At first, transfer functions were measured and analyzed. Then, these transfer functions were used in experiments where sounds from a source on the median plane were simulated and presented to subjects through headphones. In these simulation experiments, the transfer functions were smoothed by ARMA models with different degrees of simplification to investigate the role of microscopic and macroscopic patterns in the transfer functions for median plane localization. The results of the study are summarized as follows: (1) For front-rear judgment, information derived from microscopic peaks and dips in the low-frequency region (below 2 kHz) and the macroscopic patterns in the high-frequency region seems to be utilized; (2) for judgment of elevation angle, major cues exist in the high-frequency region above 5 kHz. The information in macroscopic patterns is utilized instead of that in small peaks and dips. 相似文献
13.
Fuxing Fu 《Optics Communications》2011,284(19):4563-4569
By constructing a distorted wavefront with random phase screen, the correction process of distorted wavefront has been simulated, and the correction effect of deformable mirror has been simulated and analyzed with the method of high-pass filtering. The variations of correction effect and high-frequency phase distortion have been quantitatively analyzed. The results show that the beam quality of the corrected beam degrades obviously with the increase of high-frequency phase. In addition, a new method has been presented to recover the high-frequency phase of distorted wavefront according to the given intensity distribution and low-frequency phase in near field and the intensity distribution in far field. It shows that the method is very effective to recover the high-frequency phase of distorted wavefront. 相似文献
14.
I. V. Andronov 《Acoustical Physics》2013,59(4):369-372
The problem of scattering of a high-frequency plane wave incident at a small angle to the axis of a strongly elongated spheroid is studied. The asymptotic formula for the scattering cross section is obtained in the case of ideal boundary conditions. The influence of the elongation rate of the spheroid and the angle of incidence of the plane wave is analyzed based on computations. 相似文献
15.
An analysis of the parameters of nonlinear waves transmitted through a layer of a randomly inhomogeneous medium is carried
out. The layer is modeled by a two-dimensional phase screen. Passing through the screen plane, the wave acquires a random
phase shift. The wave front becomes distorted, and randomly located regions of ray convergence and divergence are formed,
in which the nonlinear evolution of the wave alters profoundly. The problem is solved in the approximation of geometrical
acoustics. The ray pattern of a plane wave transmitted through the regular screen is constructed. The solution that describes
the spatial structure of the field and the evolution of an arbitrary temporal wave profile behind the screen is obtained.
Statistical characteristics of the discontinuity amplitude are calculated for different distances from the screen. A random
modulation is shown to result in a faster (in comparison with the case of a homogeneous medium) nonlinear attenuation of the
wave and in the smoothing of the shock profile. The distribution function of the wave field parameters becomes broader because
of random focusing effects. 相似文献
16.
V. G. Gusev 《Russian Physics Journal》1997,40(7):659-663
The formation of a lateral-shear speckle interference pattern in bands of infinite width in two-exposure recording of the
Fourier speckle pattern of a ground-glass screen by a negative lens is analyzed. It is demonstrated theoretically and experimentally
that an interference pattern is localized in the Fourier plane during reconstruction; that patterns is characterized by axial
wave aberrations of the lens and optical system used in the channel illuminating the ground-glass screen, with twice the sensitivity
for a fixed lateral shear. In the particular case when the lens is in the plane of the ground glass screen the interference
pattern characterizes the axisymmetric wave front aberrations.
Tomsk State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, p. 72–78, July, 1997. 相似文献
17.
By using the method of the power-spectrum inversion, the turbulence phase screen has been built up, and the propagation characteristics of high-frequency phase of laser beam in atmospheric turbulence have been analyzed; in addition, the phase correction effect of laser beams by using the adaptive deformable mirror has been simulated, and its affecting factors in turbulence have also been analyzed quantitatively. The results show that the phase correction effect of laser beams in turbulence is mostly determined by the percent of high-frequency phase in distorted wavefront. With the increase of the intensity of atmospheric turbulence and the propagation distance in turbulence, the percent of high-frequency phase in distorted wavefront increases, resulting in the degradation of the phase correction effect. 相似文献
18.
19.
A. Wünsche 《Annalen der Physik》1975,487(6):401-424
Reflection and Refraction of Light by an Anisotropic Layer The linear problem of reflection and refraction of plane monochromatic electromagnetic waves by a plane-parallel homogeneous anisotropic layer between (in general different) homogeneous optically isotropic semiinfinite media is treated on the basis of MAXWELL 's equations and the boundary conditions following from them. The permittivity tensor of the anisotropic layer is assumed to be widely arbitrary and therefore asymmetric, neglecting only the spatial dispersion, i. e., the dependence on the wave vector. The electrical fields of reflected, refracted, and transmitted waves are calculated in dependence on the electric field of the incident wave. The conditions for waveguide modes of the layer in the absence of incident waves are obtained from the vanishing of a determinant. The general formulae are specialized to the cases of normal incidence and also of perpendicular and parallel polarisation, relatively to the plane of incidence, of the refracted partial waves in the anisotropic layer thus obtaining simplifications in these cases. The interesting cases of uniaxial layers, when the optic axis lies either parallel or perpendicular to the plane of incidence, belong to the last mentioned special cases of perpendicular and parallel polarisation relatively to the plane of incidence. 相似文献
20.
Sound source localization on the horizontal plane is primarily determined by interaural time differences (ITDs) for low-frequency stimuli and by interaural level differences (ILDs) for high-frequency stimuli, but ITDs in high-frequency complex stimuli can also be used for localization. Of interest here is the relationship between the processing of high-frequency ITDs and that of low-frequency ITDs and high-frequency ILDs. A few similarities in human performance with high- and low-frequency ITDs have been taken as evidence for similar ITD processing across frequency regions. However, such similarities, unless accompanied by differences between ITD and ILD performance on the same measure, could potentially reflect processing attributes common to both ITDs and ILDs rather than to ITDs only. In the present experiment, both learning and variability patterns in human discrimination of ITDs in high-frequency amplitude-modulated tones were examined and compared to previously obtained data with low-frequency ITDs and high-frequency ILDs. Both patterns for high-frequency ITDs were more similar to those for low-frequency ITDs than for high-frequency ILDs. These results thus add to the evidence supporting similar ITD processing across frequency regions, and further suggest that both high- and low-frequency ITD processing is less modifiable and more noisy than ILD processing. 相似文献