共查询到20条相似文献,搜索用时 609 毫秒
1.
This paper is primarily aimed at experimental verification of results of theoretical studies of the possibility of concentration of an electromagnetic wave on areas of a size much smaller than the wavelength λ with the help of doubly connected narrowing waveguides. Fundamentally important experimental results, in both the microwave and optical ranges, have been obtained on an installation containing a biconical horn in the form of a conical needle and a metal plane. A fundamental convergent mode has been excited. A reflected fundamental mode appeared and changed sharply as the vertex of the conical needle approached the plane at a distance of the order of several nanometers and closer. The predictions of the theory concerning the concentration of electromagnetic (microwave and optical) radiation in a biconical horn onto objects with a size of the order of a nanometer with almost no losses have been confirmed experimentally. The possibility of increasing the sensitivity of the methods of spectroscopy of individual impurity sites using a biconical horn for coupling with the near field of a quantum oscillator (atom, molecule) in a quasi-stationary region is also investigated. The efficiency of electric-dipole radiation emission into a biconical horn increases by a factor of (λ/r0)4 compared to spontaneous radiation into free space (here λ is the wavelength and r0 is the distance from the dipole to the horn input). We have shown experimentally that it is possible in principle to create a device functioning as a sensor (a near-field electromagnetic microscope) and as an instrument of the action by a strong electromagnetic field (simultaneously at several frequencies) with a spatial resolution of the order of 1 nm in the optical and microwave ranges. Results of experiments of other authors are discussed in terms of concepts of convergent and divergent waves in a biconical horn. The feasibility of extending these methods to the extreme UV and soft x-ray ranges is pointed out. 相似文献
2.
We investigate the nonlinear optical interaction through a periodic waveguide structure consisting of two alternating segments with different linear and nonlinear optical properties. A coupled equation system has been used to calculate the intensity of fundamental and second harmonic waves and the phase shift of the fundamental. The model has been experimentally tested with good results, but the effect of the phase shift has not been considered. Comparison with the quasi-phase match (QPM) technique has been presented. The novel features introduced by alternating segments with different linear and nonlinear optical properties have been discussed. The model shows a more flexible approach, which can be used in designing optical components based on coherent nonlinear interaction. Applications are straightforward for frequency doubler and all-optical switch. 相似文献
3.
Kenji Takada Minoru Ueda Kohji Minami Masayuki Nishikawa Hideaki Fujita Shohzou Minamide 《Optical Review》2008,15(2):130-132
We present a novel approach to the miniaturization of an imaging system with high resolution and high optical magnification
for camera phones. An optical zoom system with a mechanical shutter has been designed and developed, the mechanical shutter
being necessary to assure high image quality. The shutter is integrated with the zooming lens group, which allows the zoom
lens unit to be downsized. Performance of the zoom lens unit accommodates an image sensor of over five-mega-pixels and fulfills
all the requirements of a camera phone. 相似文献
4.
后向散射式路道能见度激光测量仪的研究 总被引:4,自引:0,他引:4
后向散射式跑道能见度激光测量仪主要由光学发射与接收系统、信号放大与处理系统及显示系统三部分组成。其中,光学发射与接收系统主要包括:Nd :YAG 激光器、倍频器、准直镜、扩束镜、光学接收镜头、截止滤光片、窄带干涉滤光片及光电转换系统等;信号放大与处理系统主要包括:小信号放大电路、延时电路、采样保持电路、多路模拟开关、模 数转换电路及8031 单片机等;显示系统主要由数字显示器、打印机及接口电路等组成。介绍了该测量仪的工作原理、基本结构和主要技术指标,讨论了其中的技术难点及其相应的解决方法。 相似文献
5.
A new approach to control the linear dimensions of analytical electrophysical systems is suggested. This approach uses the lens properties of electron–optical elements with a curvilinear axis. It is shown that such an approach can be effectively applied, in particular, to synthesize ion–optical systems (IOSs) for static magnetic mass spectrometers and can be implemented owing to off-axis fundamental points, the “poles” of an electron–optical system, introduced earlier by one of the authors. The capabilities of the new approach are demonstrated with the synthesis of the IOS of a static mass spectrometer dedicated for isotopic and chemical analysis with an increased resolution. A new IOS not only provides desired high ion–optical parameters at decreased dimensions of the mass spectrometer as a whole but also makes it possible to loosen requirements for the manufacturing accuracy of IOS main elements. 相似文献
6.
This article presents an approximate solution for weak nonlinear standing waves in the interior of an exponential acoustic horn. An analytical approach is chosen assuming one-dimensional plane-wave propagation in a lossless fluid within an exponential horn. The model developed for the propagation of finite-amplitude waves includes linear reflections at the throat and at the mouth of the horn, and neglects boundary layer effects. Starting from the one-dimensional continuity and momentum equations and an isentropic pressure-density relation in Eulerian coordinates, a perturbation analysis is used to obtain a hierarchy of wave equations with nonlinear source terms. Green's theorem is used to obtain a formal solution of the inhomogeneous equation which takes into account linear reflections at the ends of the horn, and the solution is applied to the nonlinear horn problem to yield the acoustic pressure for each order, first in the frequency and then in the time domain. In order to validate the model, an experimental setup for measuring fundamental and second harmonic pressures inside the horn has been developed. For an imposed throat fundamental level, good agreement is obtained between predicted and measured levels (fundamental and second harmonic) at the mouth of the horn. 相似文献
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8.
Q. Wu P. Pan F.-Y. Meng L.-W. Li J. Wu 《Applied Physics A: Materials Science & Processing》2007,87(2):151-156
In this paper, a horn antenna filled with a metamaterial structure as lens inner the aperture is presented. Unlike conventional
curve lenses, the lens is designed in the present work using a fully flat structure, which results in a great improvement
for the directivity of the horn antenna based on the zero refraction characteristics of the metamaterial. In this structure,
a periodic-structure metamaterial with three-layer metal grids is designed using the CST Microwave Studio for optimization
and its zero refraction property is validated. For the characterization of the antenna, the electric-field distribution in
radiation area, reflection parameter (S11), gain and radiation pattern are calculated. The results show that the gain of a wide flare angle horn antenna is enhanced
with over 2 dB between 16.10–17.30 GHz after the metamaterial is utilized. Therefore, the metamaterial lens horn structure
results in a miniaturized antenna design approach compared to the optimum conventional horn of the same aperture size and
gain in the interested frequency band.
PACS 78.70.Gq; 81.05.Zx; 84.40.Ba 相似文献
9.
Fangxin Li 《Optics Communications》2007,274(1):59-65
Real-time Fourier transformation (RTFT) of optical waveforms in amplitude and phase (i.e. transform-limited RTFT) is a fundamental operation that enables the realization of many interesting ultrafast signal processing applications, including wavelength-tunable optical pulse filtering, all-optical temporal correlations and convolutions and temporal imaging, among others. In this paper, we demonstrate that under certain conditions, a single time lens (quadratic-phase temporal modulator) followed by a suitable dispersive delay line can be used to implement transform-limited RTFT of optical pulses. The design specifications and constraints of the proposed transform-limited RTFT systems are derived and discussed. As compared with the conventional methods, the proposed design does not require the use of an input dispersive device preceding the time lens or a second time lens after dispersion, thus resulting in a simpler and more practical alternative for implementing TL-RTFT of optical signals. The feasibility of our proposal to operate on picosecond optical waveforms using electro-optic time lenses has been confirmed by numerical simulations. 相似文献
10.
W. B. Dou Z. L. Sun X. Q. Tan 《International Journal of Infrared and Millimeter Waves》1999,20(10):1843-1854
The fields refracted by circular symmetric hyperbolic lens illuminated by a linearly polarized plane wave are calculated from the induced surface currents. It is shown that the fields in the axial region approximate to the fields in the aperture of corrugated horn under balanced hybrid condition. The image structures for different focal ratio are compared with the classical Airy pattern, deduced by scalar analysis, of optical focusing systems. The coupling between the lens and a corrugated horn at different position on focal plane are presented. The lens resolution and pix numbers are evaluated. 相似文献
11.
R.A. Gunasekaran M. Agarwal A. Singh P. Dubasi P. Coane K. Varahramyan 《Optics and Lasers in Engineering》2005,43(6):1086
A novel small fluid controlled optical lens system that is capable of displaying dynamic variation of its focal length and field-of-view (FOV) is designed and fabricated. In this active lens system, appropriate volume of the optical fluid can be pumped into or out of the lens chamber to provide double-convex (DCX) or double-concave (DCV) lens effect. Simple optical imaging experiments were performed using different sets of glass lenses with fixed focal lengths to determine the optimum lens configuration required for designing a dynamic optical lens system. The experimental results obtained from the glass lenses demonstrate that a combination of a single DCX lens with three DCV lenses provides a wider FOV. The flexible membranes for fluid controlled lenses were fabricated using polydimethylsiloxane polymer material, which has good optical transparency and elasticity. A simple fluid injection system is used to vary the radius of curvature of the lenses, and thereby to change the focal length. A dynamic optical lens system with a combination of one DCX and multiple variable focal length DCV lenses as designed here can image an object with a wide range of focal length and FOV. With this fluid controlled optical system, the FOV and focal length could be continuously varied and a maximum FOV of 118.3° could be achieved. The smallest f-number (f/#) for this fluid controlled single lens system was found to be 1.3, which corresponds to the numerical aperture value of 0.35. 相似文献
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Using the Fresnel–Kirchhoff diffraction integral, the intensity distribution and encircled energy of a singular beam at the focal plane of a lens, has been numerically evaluated in the presence of astigmatism and defocusing. Study has been made for two values of topological charge. The aberration results in flattening of dark core and the effect is more pronounced for beam with double topological charge. Twofold symmetry in intensity distribution is observed for selected values of defocusing. The results have been verified by the optical transfer function (OTF) approach. 相似文献
14.
为实现光学透镜曲率半径的快速准确测量,设计了一种基于自动对焦技术的非接触式透镜曲率半径测量方案。测量系统分别在被测透镜表面的顶点位置和曲率中心位置自动对焦,系统所记录的两个位置之间的距离即为曲率半径。针对透镜曲率半径检测应用,对自动对焦技术进行了改进:将连通区域提取技术应用于定位目标图像,提高了清晰度评价函数的灵敏度;利用均值比较法和三点法改进了传统爬山搜索策略。实验结果表明:基于自动对焦技术的透镜曲率半径检测是有效的,测量误差低于0.196%,测量重复性好于0.109%。该方法已经成功应用于透镜曲率半径测量仪。 相似文献
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针对惯性约束聚变(ICF)激光等离子体诊断系统应用的需求,提出一种采用非线性相位拟合法设计单透镜代替理想对数轴锥镜的方法。对所要得到的球面透镜与理想对数轴锥镜的相位进行拟合,求解得出所需要的球面透镜参量。设计了用于激光等离子体诊断系统的长焦深透镜,并对透镜的焦深、轴向光场均匀性、横向均匀性、焦斑旁瓣等指标进行分析。数值分析结果表明,长焦深透镜具有与理想对数轴锥镜相同的相位分布,焦深、轴向光场均匀性、横向均匀性、焦斑旁瓣均符合设计要求,验证了非线性相位拟合法的正确性。 相似文献
17.
在使用LED作为照明光源的过程中,光场作为LED应用中的关键因素,一般使用二次光学系统进行调控。但是二次光学系统一般设计复杂、体积大、重量重,随着LED光学封装系统朝着小型化方向发展,二次光学系统的应用将会变得困难。结合软件仿真和实验验证探索了用于单片集成发光二极管(MI-LED)的一次光学透镜的光场调控功能。研究结果表明,仿真和实验LED光源的光场几乎重合一致,所设计的一次透镜将LED光源的光束角从120°调控到48°~72°范围内。与未加一次透镜的LED光源相比,加一次透镜的LED光源具有更高的光提取效率和更均匀的空间光色分布。 相似文献
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大孔径红外光学系统往往易受自重和环境温度影响造成像质恶化,引入自适应光学技术的红外自适应系统能够很好地解决该问题,为此设计了一个用于Hartmann-Shack波前检测的红外自适应光学系统。重点设计了10×可见光与中波红外双波段望远镜,物镜为卡赛格林反射物镜组,无需消色差,在可见光与中波红外2个波段实现了消色差目镜设计;还设计了红外成像中继光学系统,可实现100%冷光阑效率,并补偿望远镜在中波红外波段的残余像差,使最终设计的光学系统MTF接近衍射极限,达到了0.5以上,满足设计指标要求。 相似文献
20.
根据微型纤维软镜小尺寸、大视场的要求, 分析其设计准则, 采用"负-正"型反远距物镜作为初始结构, 确定其为像方远心光学系统。通过理论计算和Zemax光学仿真软件的不断优化, 最终设计出了一个工作波段在0.48 μm~0.65 μm, 焦距为0.37 mm, 全视场90°, 相对孔径为1:4的微型光纤传像束内窥镜物镜。该物镜由4片透镜组成, 包括1片负透镜、1片正透镜和1片双胶合透镜。设计结果表明:镜头总长3.89 mm, 最大横截面直径0.95 mm, 满足像方远心光学系统的初始设计要求, 在奈奎斯特空间频率77 lp/mm处的调制传递函数(MTF)近似为0.7, 接近衍射极限, 并且具有小尺寸、大视场、像质优良、结构合理、像面光照强度均匀等特点, 符合微型纤维式内窥镜的使用条件。 相似文献