渐进多焦点眼用镜片的子午线设计研究

介绍渐进多焦点眼用镜片的构造,论述镜片的设计思想,阐述渐进多焦点眼用镜片子午线设计的基本原理,构建子午线多项式,给出子午线设计需满足的准则.在子午线设计的基础上,设计渐进多焦点眼用镜片等屈光度轮廓线,确定镜片面形,并求出镜片平均球面度与像散.比较3种不同子午线设计的渐进多焦点眼用镜片,并进行实际加工与检测.研究结果表明,子午线设计是渐进多焦点眼用镜片设计的关键之一,不同的子午线屈光度分布,对应的渐进多焦点眼用镜片的球面度、像散以及畸变等差别较大.依据实际设计与检测结果,给出适用于不同个性化需求的渐进多焦点眼用镜片子午线屈光度分布的规律.     

Nonlinear intensity-related magneto-optical Kerr effects in the planar geometry

The reflection of an electromagnetic wave at the second-harmonic frequency from a semi-infinite optically isotropic magnetic medium for the directions of uniform magnetization corresponding to the meridional and equatorial Kerr effects is considered. Using the Green’s tensor function technique, in the first approximation in magnetization, the expressions for complex amplitudes of the field are obtained for the s and p polarizations of the incident beam and their superpositions. It is shown that in the latter case, the meridional effect becomes intensity-related. Dependences of the intensity-related meridional and equatorial Kerr effects on the angle characterizing polarization of the pump wave are obtained by numerical calculations. A comparative analysis of the linear and nonlinear Kerr effects is made.     

Geometrical optics of lightguides with an oblique input end-face

The geometrical-optics relations between meridional rays of incidence and maximum aperture have been derived for the general case of a lightguide with an oblique input end-face. It is shown that the maximum angles of incidence are asymmetrical with respect to both the axis of the lightguide and the normal to the input end-face. A numerical comparison shows that for a light-guide with an oblique input end-face, in the meridional ray case, a greater or smaller angle of aperture may result, depending on the cutting angle, compared with that for a lightguide input end-face perpendicular to the optical axis. A greater angle of aperture is especially important since it means an improvement in the launching efficiency of incoherent light sources. Moreover, the maximum angle of aperture has been derived for the generalized light guide in which successive total internal reflections at the cladding/surroundings interface have been taken into account.     

Analysis of axisymmetric shell structures under axisymmetric loading by the flexibility method

A method is developed for the static stress and deformation analysis of axisymmetric shells under axisymmetric loading by reduction of the shell to ring sections. In particular, the wall thickness of the shell may vary and the method is applicable to the analysis of shells with irregular meridional geometry. Explicit expressions for the influence coefficients for each ring element are derived. In the development of these expressions, exact evaluation of stresses in the circumferential direction of the ring is used. The distribution of stresses in the meridional direction of the ring element is assumed to be linear with each element. By using the derived influence coefficients, the unknown forces at the junctures of the ring elements are found by the standard flexibility method of indeterminate structural analysis. Subsequently, the displacements and internal stresses are determined. Example solutions for a flat circular plate under transverse loading and for a cylindrical shell under a boundary edge loading show excellent agreement with solutions found by solving the governing differential equations.     

Polarization description of light fields in terms of meridional and azimuthal vectorial features

In terms of the radial, azimuthal and longitudinal components of the field, the polarization features of 3D electromagnetic beams are described by defining three local parameters, namely, the so-called 3D degree of meridional polarization, the ratio between meridional and azimuthal contributions and the degree of cross-correlation between meridional and azimuthal field components. At each point Q, the term “meridional” refers to the projection of the electric field vector onto a plane containing the point Q and the longitudinal axis z. These parameters are valid for both paraxial and non-paraxial regimes. Accordingly, they can be used for describing highly-focused fields. The analytical relation among the well-known 3D electromagnetic degree of polarization and the above parameters is also obtained, and several simple cases are considered.     

The meridional circulation of the Sun: Observations,theory and connections with the solar dynamo

The meridional circulation of the Sun, which is observed to be poleward at the surface, should have a return flow at some depth. Since large-scale flows like the differential rotation and the meridional circulation are driven by turbulent stresses in the convection zone, these flows are expected to remain confined within this zone. Current observational(based on helioseismology)and theoretical(based on dynamo theory) evidences point towards an equatorward return flow of the meridional circulation at the bottom of the convection zone. Assuming the mean values of various quantities averaged over turbulence to be axisymmetric,we study the large-scale flows in solar-like stars on the basis of a 2D mean field theory. Turbulent stresses in a rotating star can transport angular momentum, setting up a differential rotation. The meridional circulation arises from a slight imbalance between two terms which try to drive it in opposite directions: a thermal wind term(arising out of the higher efficiency of convective heat transport in the polar regions) and a centrifugal term(arising out of the differential rotation). To make these terms comparable,the poles of the Sun should be slightly hotter than the equator. We discuss the important role played by the meridional circulation in the flux transport dynamo model. The poloidal field generated by the Babcock-Leighton process at the surface is advected poleward, whereas the toroidal field produced at the bottom of the convection zone is advected equatorward. The fluctuations in the meridional circulation(with coherence time of about 30-40 yr) help in explaining many aspects of the irregularities in the solar cycle. Finally, we discuss how the Lorentz force of the dynamo-generated magnetic field can cause periodic variations in the large-scale flows with the solar cycle.     

Eddy forced mean meridional circulation

Summary The atmospheric mean meridional circulation is diagnostically evaluated from the annual mean data by Oort and Rasmusson (1971). Starting from the primitive equations, assuming small errors in the data set and using a variational method, two independent second-order equations for the mean meridional circulation are derived, one from the vorticity balance and the other from the thermodynamic balance. By assuming uniform errors, and taking into account only the horizontal component of the eddy fluxes of heat, momentum and geopotential, the mean meridional circulation is computed and the results of the different methods are then compared.     

On 2D Focusing of X rays Bragg-diffracted by a biaxially bent crystal

2D focusing of an X-ray wave Bragg-diffracted by a biaxially bent crystal is considered in terms of quasi-back diffraction scattering in the meridional plane. Analytical expressions for the focusing geometrical condition in the meridional plane and for the spatial distribution of the wave intensity in the same plane in the neighborhood of the point source image are derived. They differ from those currently available from the theory.     

Legendre transformation: Connection between transverse aberration of an optical system and its caustic

A geometrical theory of aberration has been developed, using caustic surfaces. This theory is based upon the properties of the Legendre transformation, which connects the caustic surface with the transverse aberration of the optical system in the meridional plane.     

Influence of interactive stratospheric chemistry on large-scale air mass exchange in a global circulation model

A new globally uniform Lagrangian transport scheme for large ensembles of passive tracer particles is presented and applied to wind data from a coupled atmosphere-ocean climate model that includes interactive dynamical feedback with stratospheric chemistry. This feedback from the chemistry is found to enhance large-scale meridional air mass exchange in the northern winter stratosphere as well as intrusion of stratospheric air into the troposphere, where both effects are due to a weakened polar vortex.     

Parameters optimization and phase analysis of decentered grating stretchers

A decentered grating stretcher for chirped pulse amplification systems is analyzed with oblique meridional ray tracing. Several formulae and conclusions are developed to design and optimize the stretcher. On basis of an analytical phase expression with an explicit significance, the expressions of the second-, third- and approximate fourth-order phases at the central wavelength are presented with only independent variables. These simplify the parameter design for this kind of stretcher and the phase compensation design of the whole amplifier system, which has been demonstrated with a practical example.     

Meridional ray backscattering enhancements for empty truncated tilted cylindrical shells: measurements,ray model,and effects of a mode threshold

Narrow-band backscattering experiments are used to characterize a meridional ray enhancement on a tilted, finite empty cylindrical shell having a blunt truncation. The meridional ray of the lowest order flexural leaky Lamb wave is examined, which has previously been shown to lead to large backscattering enhancements for excitation frequencies near and above the shell's coincidence frequency. The measurements are used to validate a convolution formulation ray theory describing the far-field backscattered amplitudes. Comparisons are also made with an approximate partial wave series solution for the finite cylindrical shell. The amplitude of the meridional ray enhancement is dependent on the nature of the reflection of the leaky wave from the shell truncation. While the peak measured amplitude agrees with predictions at low frequencies, experiments indicate the enhancement is degraded at high frequencies and exhibits an abrupt drop near the frequency of the mode threshold (cutoff) for the next-highest flexural mode. The nature of the leaky wave end reflection is examined using an approximate calculation of the energy reflection coefficient for leaky waves on a semi-infinite free plate. Results suggest the observed degradation is the result of mode conversion effects.     

Change in the sign of the Kerr effect in ion-beam-synthesized Fe3Si films

Ion-beam-synthesized Fe₃Si thin films are studied using the magneto-optical Kerr effect, ferromagnetic resonance, electron diffraction, and Auger spectroscopy. A change in the direction of rotation of the plane-polarized light as a function of film-synthesis conditions is discovered when the meridional Kerr effect is recorded. It is shown that the observed effect is related to the presence of thin interference films with different thicknesses on the surfaces of the magnetic layers.     

四种解析解设计的短程透镜卷边对损耗的影响

根据光波导短程透镜母线曲率半径与光传输损耗的关系,利用数值计算的方法,通过计算不同母线参数条件下,四种解析解设计的短程透镜母线曲率半径,研究比较了短程透镜卷边对其损耗的影响,得出了短程透镜损耗与其有效区半径关系的曲线图,发现透镜凹面半径一定时,有效区半径越小,即卷边越大时,光传输损耗越小;短程透镜的解析改进解和最优解设计的透镜卷边存在曲率奇点.并由此得出了四种解析解设计的短程透镜有效区半径选取原则及其满足低损耗条件的取值范围.     

子午流道Bézier曲线造型中的几何问题

本文首先分析了与Bézier曲线自由度有关的问题．在此基础上提出了用五点四次Bézier曲线进行离心压气机一段子午流道造型的一种方法，它充分利用曲线自由度来满足气动和结构的要求，包括曲线端点处的曲率，同时仍有一定程度上调控曲线形状的余地．对用Bézier曲线构造的子午沈道提出了一种好用的求流道宽度（即作内切圆）的数值方法．     

宽光谱平像场全息凹面光栅的优化研究

基于凹面光栅的几何理论,推导了子午、弧矢聚焦曲线的数学表达式和全息平像场凹面光栅制作参数的计算关系式.提出了一种新的在整个使用波长范围内同时消除子午和弧矢像差的最佳优化设计方法.这种方法不同于以光线追迹技术为基础的标准光学设计软件如CODEV或ZEMAX的优化设计方法,而是从数学表达式出发,采用光栅优化因子,对凹面光栅的子午聚焦曲线和弧矢聚焦曲线进行拟合,从理论上找到最佳的能够使子午和弧矢像差同时趋于零的像平面,然后再根据拟合参数设计制作光栅.用Matlab软件解决了子午聚焦曲线超越方程无法解的困难;讨论了不同光栅常数和入射角度时对两聚焦曲线拟合程度的影响.提出了在宽光谱使用条件下,可以通过减小入射角度和光栅刻线数来提高光谱像质.     

Optics of oblique meridional and nonmeridional rays of a conicoid

Based on the exact expression for the angular eikonal of an axisymmetric conicoid (a surface formed by revolution of a second-order curve, or conic) the expressions for the Gaussian optics of oblique meridional rays are obtained, which differ from the well-known Gullstrand-Young invariants for a sphere by a set of independent arguments and contain explicitly the parameters of an optical system. The collinear properties of an optical surface with oblique meridional beams are studied. The theory of astigmatism is extended to the case of oblique nonmeridional rays, which makes it possible to construct and analyze in the first approximation the focal surfaces of an actual wide beam of rays. The theory is tested using the example of optimization of an aplanatic lens for the case of an off-axis point of an object. Based on the exact expression for the angular eikonal, definitions of integral aberrations are given. It is proposed to use the method developed in optimization of optical systems.     

Spectral characteristics of wind and air pollution data in an industrial area

Summary A comparison is made between the spectral features of sulfur dioxide concentration and zonal and meridional components of wind speed over a highly industrialized area situated on the coast. The paper focuses on the characteristic times of the meso-synoptic scale. Diurnal and longer period oscillations were identified. Variations of ground-level SO₂ concentrations are attributed to local sea-breeze circulation and to the synoptic weather period of wind speed.     

红外目标仿真光学机构

论述了目标仿真机构的用途、仿真的光学原理以及实现原理的光学系统。对其中的两个光学问题的研究作了详细地论述 ,即干扰光路 2倍于目标光路的视场角以及如何由摆镜的摆动实现。由于析光镜与光轴成 45°角 ,使像点在子午方向被拉长约为弧矢方向的 10倍。为了减少子午像差 ,将两块析光镜作成略带楔角的楔形镜。结果表明 ,由于该机构的尾焰、尾喷管用的是同一条光路 ,所以使结构大为简化 ,这对降低转动惯量非常有利 ;由于有干扰弹仿真 ,使机构的功能得到了扩大     

外视场拼接测量系统的视场拼接和交汇测量算法及其实现

基于2台外视场拼接高速电视测量仪原型样机（硬件）提出了一种将交汇测量和拼接处理相结合的算法。根据需要对地球质心和光电测量系统建立了5个坐标系,介绍了坐标系的定义及其它们之间的变换过程,给出了目标轨迹交汇测量和视场拼接的实例。用2台高速电视测量仪拼接的8台测量相机同时对同一运动目标进行测量,对获得的测量数据进行交汇和视场拼接处理,结果显示提出的拼接算法是正确、有效的,可以得到唯一解;地球曲率半径和地球子午线收敛两项影响因素得到了完全修正,表明交汇测量算法完全可以推广到其它光电测控仪器的交汇测量。