激光光束平行漂移对聚焦光斑位置影响的理论分析

本文引入象差函数分析聚焦激光光学系统焦点附近的光强分布。推导出了激光光束平行漂移对聚焦光斑位置影响的公式。分析表明,平行漂移将使聚焦光斑产生纵向焦移和横向焦移,其大小取决于光束平移量ρ_0,球差系数S_1,出瞳半径a以及高斯参考球的半球R_0。     

环状光束通过球差透镜的聚焦特性

利用偏心高斯光束相干叠加的方法,建立了柱坐标系下环状光束的新模型.从广义衍射积分理论出发,经过大量数值计算分析,详细研究了环状光束通过球差透镜的聚焦特性,定量分析了环状光束的阶数L,M、偏心高斯光束的束腰宽度w0以及球差系数C4对聚焦光场实际焦点(轴上最大光强)位置以及轴上最大光强的影响.研究结果表明,本文提出的模型可统-描述基模高斯光束和环状光束.在透镜焦距和入射光束波长一定的情况下,环状光束通过球差透镜的聚焦特性不仅与透镜的球差系数C4有关,而且还与环状光束的阶数L,M以及偏心高斯光束的束腰宽度w0有关.     

磁透镜内径比对条纹变像管性能的影响

针对一款高时空分辨率飞秒条纹变像管的带极靴磁透镜结构,提出了更加符合实际磁场分布规律的"高斯型"磁场分析模型,并且研究了磁透镜内径比对条纹变像管时间、空间分辨特性的影响。利用Lorentz软件数值研究了条纹变像管中不同内径比的磁透镜所产生的磁场分布,并且采用Monte-Carlo方法对大量光电子初始参量进行抽样计算,通过跟踪行波偏转前置短磁聚焦条纹变像管中大量光电子的运行轨迹,统计分析了光电子在最佳像面上的位置分布,最后利用调制传递函数对条纹管时空分辨能力进行评价。结果表明:当磁透镜内径比r1/r2=0.83时,磁场对电子束进行有效聚焦,获得物理时间分辨率优于190 fs,且狭缝边缘(狭缝总长度为6 mm)空间分辨率达到100 lp/mm的结果。     

强流微束斑电子束系统的研究和设计计算

本文研究了强流微束斑电子束的形成问题。提出了一种采用新型磁透镜的电磁复合聚焦系统，这种新型电子束系统的轴上磁场在电子束束腰附近达到极大值，并且轴上磁场分布关于其极大值不对称。利用附加电极在磁场较强的区域构成具有拒斥电场的电透镜，以充分抑制空间电荷推斥力的散焦作用。利用描述电流密度分布演化的变态伏拉索夫方程，研究了强流微束斑电子束系统，数值分析研究了透镜激励和电子束初始条件对于电流密度分布演化的影响。发现侧极靴透镜和相应电极形成的电磁复合聚焦场对于强电流电子束具有优秀的聚焦效果，设计出了利用侧极靴磁透镜的新型电子光学系统，这种系统可以形成电流达到1．96mA、束斑半径仅为4．2μm的强电流微束斑电子束。     

无束腰的磁浸没透镜系统的理论研究和数值模拟

采用曲轴坐标系统，导出了磁浸没透镜的宽束曲光轴理论，研究了初始正则角动量矩不为零的无束腰磁透镜系统的电子光学性质；数值模拟出了能产生缩倍聚场分布的磁透镜结构，并计算了具有解析表达式的缩倍聚场的高斯成像性质，计算结果与传统的直接计算轨迹的方法一致。     

超振荡望远成像系统中球差影响分析

在超振荡望远系统中,球差是影响其分辨本领的重要因素,其原因在于球差导致强度点扩散函数视场内产生高旁瓣,降低该系统的分辨力。本文分析了超振荡望远系统中球差对成像的影响,并确定了该系统对初级球差的容许范围。基于光学超振荡原理,利用线性规划的优化方法,设计超振荡望远系统,在532 nm工作波长下能够实现0.68倍瑞利判据的分辨力。构建针对超振荡望远系统球差的定量分析数学模型,该系统在均方根(root mean square,RMS)不超过0.041倍波长的初级球差干扰下,能分辨三缝目标物,同时分析了窄带工作波长对于该球差系统带来的成像影响。本文在光学测量、环境监视、超分辨望远等领域具有潜在的应用前景。     

无束腰的磁浸没透镜系统的理论研究和数值模拟

采用曲轴坐标系统 ,导出了磁浸没透镜的宽束曲光轴理论 ,研究了初始正则角动量矩不为零的无束腰磁透镜系统的电子光学性质 ;数值模拟出了能产生缩倍聚场分布的磁透镜结构 ,并计算了具有解析表达式的缩倍聚场的高斯成像性质 ,计算结果与传统的直接计算轨迹的方法一致     

平顶多高斯光束通过球差透镜的聚焦特性

利用广义惠更斯-菲涅耳衍射积分公式,研究了平顶多高斯光束通过球差透镜的聚焦特性。推导出轴上光强分布的表达式,并对轴上光强进行大量的数值计算及分析。研究结果表明,当平顶多高斯光束的阶数N一定时,透镜的球差将在很大程度上影响光束的聚焦特性;当透镜的球差一定时,N值的改变将影响轴上最佳聚焦点的位置;当无球差时,轴上最佳聚焦点并不在几何焦点处,轴上最佳聚焦点位置随着N值增加向几何焦点靠近,例如当阶数N由0增大为1时,则归一化最佳聚焦点由0.91增大到0.98。     

高温超导磁透镜研制成功

正近日,由中国科学院高能物理研究所为上海交通大学研制的高温超导磁透镜在上海完成了磁场测量,磁场分布结果满足设计要求,将用于电子显微镜的总装调试。电子显微镜是用于原子尺度超高时空分辨兆伏特电子衍射与成像系统,利用电子与物质作用所产生的讯号来鉴定微区域晶体结构、微细组织、化学成分、化学键结和电子分布情况的电子光学装置。用超导磁体做成的磁透镜来     

部分相干光在传输过程中的光谱异常

介绍部分相干光在通过光学透镜,光阑-透镜分离系统,杨氏实验远场及部分相干光经球差透镜聚焦后的光谱特性和光谱开关。并研究所取的参数不同,光谱开关的数量和位置会发生变化。     

复合静电-磁浸没透镜的宽束曲轴聚焦性质及像差理论

研究了新型的复合静电 磁浸没透镜的曲光轴高斯电子光学性质及像差特性。应用宽束曲轴理论 ,导出了三维局部正交坐标系中的电子运动的中心轨迹方程和曲光轴的近轴轨迹方程 ;利用数学软件Mathematica推导出了复合静电 磁浸没透镜全部曲轴二级像差系数。作为实例 ,文中针对轴上磁场和电场具有某种解析表达式的旋转对称的静电 磁浸没透镜系数 ,计算了它的曲轴高斯聚焦特性和二级像差 ,并给出了二级像差分布图形     

Aberrated lenses for generating flattened laser irradiance

Expressions for describing Gaussian beams focused by a lens with spherical aberration have been derived. Numerical results show that, when the coefficient of the spherical aberration is negative, one can obtain flattened laser irradiance at two positions along the focused field. The larger the coefficient of negative spherical aberration, the larger the flatness is. The effect of the Fresnel number of the focusing lens on the flattened laser irradiance is also investigated.     

Colorless gradient-index cylindrical lenses with high numerical apertures produced by silver-ion exchange

Colorless gradient-index cylindrical lenses with high numerical apertures in slabs 200-1000 μm thick have been fabricated by silver-sodium ion exchange in a specially developed glass. The lenses with numerical apertures of 0.6 are characterized by index profiles and by spherical and chromatic aberration. On-axis focusing properties and the application to the collimation of high-power laser diode bars are discussed.     

Effects of primary spherical aberration, coma, astigmatism and field curvature on the focusing of ultrashort pulses: homogenous illumination

We analyze the spatiotemporal intensity of pulses with durations of 20 fs and shorter and a carrier wavelength of 810 nm at the paraxial focal plane of an achromatic doublet lens. The incident pulse is well-collimated, and we use the Seidel aberration theory for thin lenses to evaluate the phase change due to the aberrations of the lens. In a set of cemented thin lenses with the stop at the lens, there is only spherical aberration, coma, astigmatism and field curvature, whereas the distortion aberration in the phase front is zero. We analyze the effect of these aberrations in the focusing of ultrashort pulses for homogenous illumination. We will show that the temporal spreading introduced by these aberrations in pulses shorter than 20 fs at 810 nm is very small but the spatial spreading is not, which reduces the intensity of the pulse considerably.     

A multislice approach to the spherical aberration theory in electron optics

Abstract

A multislice, wave-optical approach to the spherical aberration theory in electron optics is presented for the case of magnetic lenses. It is shown that, in order to remedy the inadequacy of a naive attempt carried out by taking the standard multislice equations and simply adding the fourth order terms in the transverse coordinates in the phase both of the transmission function and of the propagation kernel, it is necessary to approximate the Schrödinger equation by a wide-angle differential equation of the parabolic type and to solve it by means of a marching type algorithm. It turns out that the solution can be separated into two parts, describing, as in the multislice method, the interaction of the incoming spherically aberrated axial wavefunction with the field in a slice, and the propagation in a drift space. When the propagation is evaluated by means of the stationary phase method, a differential equation is obtained for the spherical aberration coefficient, whose solution is identical to that obtained by Glaser in his particle approach based on the eikonal.     

Influences of reference plane and direction of measurement on eye aberration measurement

We explored effects of measurement conditions on wave aberration estimates for uncorrected, axially myopic model eyes. Wave aberrations were initially referenced to either the anterior corneal pole or the natural entrance pupil of symmetrical eye models, with rays traced into the eye from infinity (into the eye) to simulate normal vision, into the eye from infinity and then back out of the eye from the retinal intercepts (into/out of the eye), or out of the eye from the retinal fovea (out of the eye). The into-the-eye and out-of-the-eye ray traces gave increases in spherical aberration as myopia increased, but the into/out-of-the-eye ray trace showed little variation in spherical aberration. Reference plane choice also affected spherical aberration. Corresponding residual aberrations were calculated after the models had been optically corrected, either by placing the object or image plane at the paraxial far point or by modifying corneas to simulate laser ablation corrections. Correcting aberrations by ablation was more complete if the original aberrations were referenced to the cornea rather than to the entrance pupil. For eyes corrected by spectacle lenses, failure to allow for effects of pupil magnification on apparent entrance pupil diameter produced larger changes in measured aberrations. The general findings regarding choice of reference plane and direction of measurement were found to be equally applicable to eyes that lacked rotational symmetry.     

Finite conjugate spherical aberration compensation in high numerical-aperture optical disc readout

Spherical aberration arising from deviations of the thickness of an optical disc substrate from a nominal value can be compensated to a great extent by illuminating the scanning objective lens with a slightly convergent or divergent beam. The optimum conjugate change and the amount and type of residual aberration are calculated analytically for an objective lens that satisfies Abbe's sine condition. The aberration sensitivity is decreased by a factor of 25 for numerical aperture values of approximately 0.85, and the residual aberrations consist mainly of the first higher-order Zernike spherical aberration term A60. The Wasserman-Wolf-Vaskas method is used to design biaspheric objective lenses that satisfy a ray condition that interpolates between the Abbe and the Herschel conditions. Requirements for coma by field use allow for only small deviations from the Abbe condition, making the analytical theory a good approximation for any objective lens used in practice.     

Caustics in a meridional plane produced by plano-convex conic lenses

We study the formation of caustic surfaces formed in both convex-plano and plano-convex conic lenses by considering a plane wave incident on the lens along the optical axis. By using the caustic formulas and a paraxial approximation, we derive analytic expressions to evaluate the spherical aberration to the third order, and a formula to reduce this aberration is provided. Furthermore, we apply the formulas to evaluate the circle of least confusion for a positive lens as a function of all parameters involved in the process of refraction through the conic lenses.     

Paraboloid–aspheric lenses free of spherical aberration

A method to design singlet paraboloid-aspheric lenses free of all orders of spherical aberration with maximum aperture is described. This work includes all parametric formulas to describe paraboloid-aspheric or aspheric-paraboloid lenses for any finite conjugated planes. It also includes the Schwarzchilds approximations (which can be used to calculate one rigorous propagation of light waves in physic optics) to design convex paraboloid-aspheric lenses for imaging an object at infinity, with explicit formulas to calculate thicknesses easily. The results were verified with software through ray tracing.