几何光学 像差、像质评价

O435．2 2005053232 人眼不同瞳孔直径波前像差特性分析=Property analysis of wavefront aberration of different human eye’s pupils [刊,中]／徐高平(中科院光电所．四川,成都(610209)),徐 翔…∥光电工程．-2005,32(7)．-38-41 采用Hartmann-Shack人眼像差仪．测量了人眼在3．1 mm,5．2 mm和6 mm瞳孔直径下的波前像差。波前像差 的RMS值表明,随着瞳孔直径的增大,人眼各阶波前像差 均随着增大。与瞳孔直径为3．1 mm时相比,瞳孔直径为 6 mm和5．2 mm时,Zernike 2～10阶波前像差的RMS值 分别增大1．2～7．7倍和1．1～4．8倍。用调制传递函数 (MTF)和Strehl比评价了高阶波前像差对成像质量的影 响。结果表明,大瞳孔高阶波前像差对成像质量的影响大 于小瞳孔;在3．1 mm,5．2 mm和6 mm瞳孔直径下,欲达 到衍射极限的Strehl比率,分别需要矫正Zernike波前像 差前2～4阶、前3～6阶和前5～7阶,需矫正的像差阶数 随瞳孔直径的增大而增加。图4参7(于晓光)     

匀速直线运动为背景的问题赏析

匀速直线运动是最简单的运动形式,但涉及到几个物体同时做匀速直线运动时,问题也并不简单. 例1:一支长为150m队伍匀速前进,通讯兵从队尾赶到队前传达命令即返回,当通讯兵回到队尾时,队伍已前进了200m,则通讯兵走过的路程为m. 析与解:这儿队伍和通讯兵都是做匀速直线运动,通讯兵从队伍的尾部赶到队前,又从队前赶到队尾,和队伍之间可以看成追赶、相遇问题. 设通讯兵的速度大小为v1,队伍前进的速度大小为v2,通讯兵从队尾赶到队前用时t1,从队前回到队尾用时t2.     

磁流变加工的连续相位板波前及光强特性

对采用磁流变抛光(MRF)工艺加工的大口径连续相位板(CPP)的波前及其光强控制特性进行了分析,对由不同的加工参数(走刀间距和走刀偏置)所加工的三组CPP进行了比较,并分析了MRF加工所引入的中频误差对CPP波前和光强特性的影响。结果表明,走刀间距为2mm、对应走刀偏置范围为0.1~0.3mm时所加工CPP的波前及其光强控制能力较差,远场有一定程度的旁瓣产生;走刀间距为2mm、偏置范围为0.4~0.5mm时所加工CPP和走刀间距为1mm、偏置范围为0.1~0.3mm时所加工CPP相比较,迭代加工效率提高,CPP波前中频误差得到一定的改善。进一步分析表明MRF所引入的中频误差对CPP波前梯度及旁瓣影响较大。     

超强飞秒激光与固体靶产生的超热电子加热机制

 在SILEX-1激光器上测量了超强飞秒激光与Ta靶相互作用产生的出射超热电子能谱及角分布,研究了出射超热电子加热机制。激光脉宽为 30 fs,激光功率密度为8.5×10¹⁸ W/cm²。靶前法线方向超热电子温度为550 keV。从实验结果可知：共振吸收是靶前法线方向超热电子主要加热机制,这与靶前存在大密度标长预等离子体的实验条件吻合。靶厚为6～50 μm时,靶后超热电子沿法线方向出射;靶厚为2 mm时,该发射峰消失。     

对“验证动量守恒定律”实验的再改进

在"验证动量守恒定律"学生实验中,现行的人教版教材的实验原理图. 设小球1滚下与球2碰撞前的速度为v0,碰撞后球1的速度为v1,球2的速度为v2.若碰撞中动量守恒,则需验证等式m1v0=m1v1+m2v2是否成立.     

内渐进多焦点镜片前表面光焦度匹配研究

研究内渐进多焦点镜片的前表面光焦度对该镜片的光焦度和散光的影响。设计出远用光焦度为2~10m-1,附加光焦度为2m-1的渐进表面数据,分别与1~10m-1的前表面光焦度匹配后输入Rotlex自由曲面检测仪转化为理论光焦度和散光度并进行统计分析。结果表明:在内渐进多焦点镜片的前表面光焦度匹配图中,存在扁椭圆区域,在该区域内匹配的内渐进多焦点镜片的远用区和近用区视觉清晰范围最大,且最大散光不大于附加光焦度。对于远用光焦度为非负的内渐进多焦点镜片,子午线上光焦度会随着前表面光焦度的增大而偏大。远用区为较大的正光焦度时,远用区和近用区清晰视觉范围明显较小。     

基于波前法的光栅拼接误差检测及计算方法

光栅拼接法是目前制作大尺寸平面衍射光栅的重要方法之一,而拼接误差是评价拼接光栅是否能够使用的重要指标之一。实时定量测量拼接误差,能够实现对拼接误差的自动闭环调整,通过实时指导拼接提高光栅拼接的精度。建立了衍射波前与光栅拼接误差关系的数学模型,分析了干涉仪测量光栅拼接误差的原理,用ZYGO干涉仪实现拼接光栅0级及-1级衍射波前的数字化定量提取,分析并计算了拼接误差波前,得到五维拼接误差的数值解。利用拼接光栅-2级的衍射波前验证五维拼接误差结果的准确性,实验结果表明由0级、-1级、-2级拼接波前计算的拼接误差具有较好的一致性,为利用波前检测光栅拼接误差并实现自动化闭环调整提供了理论指导。     

聚苯硫醚材料复合棒型换能器

本文选择了高聚物中杨氏模量较大、损耗较小的聚苯硫醚作为复合棒型换能器的前盖板.计算了聚苯硫醚棒中的纵波传播速度,研究了基于聚苯硫醚材料的复合棒型换能器的等效电路设计方法.利用有限元方法计算了换能器谐振频率、轴向应变分布、平均耗散功率等性能参数.对本文研制的前盖板为聚苯硫醚、后盖板为钢(1#)和前后盖板均为聚苯硫醚(2#...     

超短脉冲激光装置波前校正实验研究

为了提高光束质量和能量集中度,在SILEX-I超强超短脉冲钛宝石激光装置上进行了自适应光学波前校正系统实验研究,研究了波前校正系统对波前畸变、远场焦斑及能量集中度的改善情况。该系统基于相位共轭原理,主要由哈特曼波前传感器、变形镜、电控单元及控制软件等组成。实验结果表明:进行波前校正后,波前峰谷值从1.885μm下降到0.438μm,均方根值从0.379μm下降到0.052μm;远场焦斑有明显改善;超过峰值通量1/e2的区域的能量与总能量之比为72.4%。     

基于混合H_2/H_∞控制的自适应光学系统设计与仿真

为了使自适应光学系统校正后的残余波前整体倾斜小并且系统的鲁棒稳定性好,提出采用混合H2/H∞控制方法来设计自适应光学系统控制器.为了验证控制效果,通过自适应光学波前整体倾斜校正试验平台仿真了大气湍流波前整体倾斜,对比了采用混合H2/H∞控制器和采用经典积分控制器的自适应光学波前整体倾斜校正试验平台的残余波前整体倾斜以及系统的鲁棒稳定性.结果表明,相对于采用积分控制器的试验平台,采用混合H2/H∞控制器的试验平台同时获得了更小的残余波前整体倾斜和更好的鲁棒稳定性,证明了自适应光学系统混合H2/H∞控制方法的有效性.     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.     

A stereo matching algorithm using multi-peak candidate matches and geometric constraints

Gray cross correlation matching technique is adopted to extract candidate matches with gray cross correla- tion coefficients less than some certain range of maximal correlation coefficient called multi-peak candidate matches. Multi-peak candidates are extracted corresponding to three closest feature points at first. The corresponding multi-peak candidate matches are used to construct the model polygon. Correspondence is determined based on the local geometric relations between the three feature points and the multi-peak candidates. The disparity test and the global consistency checkout are applied to eliminate the remaining ambiguous matches that are not removed by the local geometric relational test. Experimental results show that the proposed algorithm is feasible and accurate.