小口径双通道球幕投影镜头的设计

为提高球幕投影成像质量,提出了双通道球幕投影方案,并基于此方案,为3.05 cm(1.2英寸)3DMD芯片技术投影机设计了双通道球幕投影镜头。根据投影方案确定了设计指标,对初始结构的选型做出了合理的分析,阐述了光学设计过程,给出了像差优化及设计结果的评价。为避免镜头口径过大引起的重心不稳,通过合理控制光线入射高度,将镜头首片透镜的口径进行了大幅度的压缩,最终口径仅为102 mm。设计的成像质量高、像质均匀的球幕双拼投影镜头F#为2.5,反远比为6:1,1.0视场在38 lp/mm的Nyquist频率处MTF值为0.5,0.85以内视场的MTF值达到0.65以上,最大横向色差为4.7 μm,小于0.5 pixel。     

通用型数字鱼眼镜头检测系统的设计

设计了一种通用型数字鱼眼镜头检测系统,由照明系统、检测标板、等效平行平板系统和球幕组成。照明系统内部设有平面反光镜、柱体蝇眼透镜阵列、准直物镜,起到了缩小系统体积,提高光能利用率和照明均匀性,以及实现照明光斑大小尺寸可调的作用。其球幕内壁刻有角度分划尺,用于测量被测镜头的视场角。测试系统的照明视场范围为φ8.1 mm~φ36.3 mm,照度均匀度达到91%,光通量大于5 000 lm,且大小可调。检测系统可实现对芯片尺寸为0.55″~1.55″的1DLP、3DLP、3LCD、3LCOS的各种类型的数字投影或放映鱼眼镜头的像方视场角、分辨率、彩色还原性能、色差等性能和放映效果进行测试,降低了检测成本,通用性强。     

球幕投影数字鱼眼镜头的光学设计

采用非相似成像原理,利用Zemax光学软件设计了一款适用于1-60 cm(0.63英寸)3LCD数字投影机的球幕投影数字鱼眼镜头。镜头结构是一种反远距型光学结构,由5组6片球面透镜组成,具有结构简单、易加工等特点。镜头全视场角为180,焦距为3.28 mm,相对孔径为1/1.9,后工作距离为35.8 mm,光学总长为196 mm。镜头具有较高的成像质量,在50 lp/mm处,各个视场的MTF值均大于0.4,最大垂轴色差为4.5 m,全视场的F-theta畸变绝对值小于3%,最大视场的像面相对照度达到96.27%。     

宽视场成像光谱仪前置远心离轴三反光学系统设计

为了满足宽视场成像光谱仪发展的需求,研究了远心、宽视场和大相对孔径的离轴三反系统的光学设计问题,推导出平像场远心三反系统初始结构尺寸参数和三级像差表达式.针对光谱范围0.4～2.5μm、F数为4、有效焦距720 mm和视场10°的设计要求,采用视场角离轴的方法,设计出次镜为凸球面镜、主镜和三镜共面且都为凹二次曲面镜以及...     

球幕鱼眼镜头及其点列图计算

本文讨论了视场等于180度的球幕鱼眼镜头的光学设计问题。介绍了它的应用和成象原理。球幕直径为24米。依据象差渐晕理论,追迹了一系列子午和弧矢光线以及空间光线从而可以绘制点列图。通过实例给出了有关象质信息。     

大视场紫外告警相机光学系统研究与设计

为了提高紫外探测器系统的信噪比,确保紫外告警相机的低虚警率,分析与研究了大视场紫外光学系统的结构型式,采用反远距、准像方远心光路,实现了大视场光学系统的像差校正,使系统具有优良的成像质量及均匀的像面照度.设计了波段范围为0.254~0.272μm、视场角为110°、相对孔径为1/3的光学系统.系统成像质量良好,畸变小,像面照度均匀.成像质量分析结果表明:全视场最大弥散斑半径小于53.7μm,轴上、轴外视场像面照度均匀性小于15%,0.85视场的相对畸变小于20%,满足紫外告警相机的使用要求.     

共形光学系统瞬时视场外杂散光的分析及处理

针对空间成像光学系统的像质容易受到瞬时视场外杂散辐射的影响,利用杂散光分析软件建立一个共形光学系统光学机械结构模型,并对其进行反向光线追迹,从而确定出该系统中对瞬时视场外杂散辐射光的聚集贡献较大的关键表面及视场外杂散辐射光的主要传递路径.采用在系统中加入多级挡光环辅助结构的方式获得了100%的瞬时视场外杂散光屏蔽效果.该设计方案具有简单易行的特点.     

折/衍混合的红外双视场光学系统设计

为了实现红外双视场光学系统两个视场间的快速切换,同时满足便携式及易安装的需求,设计了一种轻量化的折/衍混合红外双视场光学系统.系统采用折/衍混合和二次成像光学结构,利用光学设计软件对系统进行优化,评价了系统的像质,分析了系统温度补偿问题并给出其温度调焦曲线.系统工作波长为3.7～4.8 μm,能实现120 mm/60 mm两档焦距变换.设计结果表明,冷光阑效率达到100%,在探测器的Nyquist频率33 lp/mm处,轴外视场光学系统的调制传递函数大于0.3,系统光学总长为200 mm.整个系统包括7块透镜,只需移动一片透镜就能完成双视场的转换,结构简单,实现了轻量化和高质量成像.     

静止轨道高光谱海洋水色仪光学系统设计

设计了由超大口径前置望远系统和超大视场光谱仪组成的超大口径高光谱海洋水色仪.前置望远系统采用同轴三反光学系统结构,口径为4 m,视场为0.64°,焦距为21.6 m,波段范围为400~1 000nm.超大视场光谱仪采用改进的Offner结构,视场为240mm,光谱分辨率为10nm.探测器像元尺寸为15μm×15μm,4片探测器交错拼接实现400km幅宽.超大视场光谱仪在400~1 000nm的宽波段内,点列图半径的均方根值均小于3.9μm,静止轨道高光谱海洋水色仪全系统不同波长的MTF在33.3lp/mm处大于0.52,各项指标均满足应用要求.     

折/衍混合的红外双视场光学系统设计

为了实现红外双视场光学系统两个视场间的快速切换,同时满足便携式及易安装的需求,设计了一种轻量化的折/衍混合红外双视场光学系统.系统采用折/衍混合和二次成像光学结构,利用光学设计软件对系统进行优化,评价了系统的像质,分析了系统温度补偿问题并给出其温度调焦曲线.系统工作波长为3.7～4.8μm,能实现120mm/60mm两档焦距变换.设计结果表明,冷光阑效率达到100%,在探测器的Nyquist频率33lp/mm处,轴外视场光学系统的调制传递函数大于0.3,系统光学总长为200mm.整个系统包括7块透镜,只需移动一片透镜就能完成双视场的转换,结构简单,实现了轻量化和高质量成像.     

Flow stability of a liquid dielectric cylinder in a transverse electrostatic field

A perturbation method is used to study the stability of the interface between a cylinder formed by the flow of an inviscid liquid dielectric and air in the presence of an external electrostatic field produced by coaxial electrodes. The field is perpendicular to the interface. The outer electrode is at a potential V₀ and the inner electrode is grounded. An equation is found for the neutral-equilibrium curve, and the threshhold values of V₀, i.e., those at which the surface becomes unstable, are calculated for the case in which the outer radius of the stream is twice the inner radius.Translated from Izvestiya VUZ. Fizika, No. 12, pp. 34–38, December, 1969.     

On the theory of polarization radiation in media with sharp boundaries

Polarization radiation generated when a point charge moves uniformly along a straight line in vacuum in the vicinity of media with a finite permittivity ɛ(ω) = ɛ′ + iɛ″ and sharp boundaries is considered. A method is developed in which polarization radiation is represented as the field of the current induced in the substance by the field of the moving charge. The solution to the problem of radiation induced when a charge moves along the axis of a cylindrical vacuum channel in a thin screen with a finite radius and a finite permittivity is obtained. Depending on the parameters of the problem, this solution describes various types of radiation (Cherenkov, transition, and diffraction radiation). In particular, when the channel radius tends to zero and the outer radius of the screen tends to infinity, the expression derived for the emitted energy coincides with the known solution for transition radiation in a plate. In another particular case of ideal conductivity (ɛ″ → ∞), the relevant formula coincides with the known results for diffraction radiation from a circular aperture in an infinitely thin screen. The solution is obtained to the problem of radiation generated when the charge flies near a thin rectangular screen with a finite permittivity. This solution describes the diffraction and Cherenkov mechanisms of radiation and takes into account possible multiple re-reflections of radiation in the screen. The solution to the problem of radiation generated when a particles flies near a thin grating consisting of a finite number of strips having a rectangular cross section and a finite permittivity and separated by vacuum gaps (Smith-Purcell radiation) is also obtained. In the special case of ideal conductivity, the expression derived for the emitted energy coincides with the known result in the model of surface currents.     

非相干光对共聚焦显微镜层析能力的影响

在共聚焦显微镜中,通过系统的归一化轴向光强半高宽与探测器有效半径和非相干光源有效半径的关系曲线,获得非相干光源照明下系统光学层析能力的变化规律.发现当探测器和光源的有效半径都小于3时,系统具有较好的光学层析能力;其他情况下,系统光学层析能力下降且会受入射光场分布的影响.     

Propagation of waves radiated by a stochastic screen in dielectric media

Propagation of electromagnetic waves radiated by a stochastic screen bounding dielectric media has been investigated. Two statistical characteristics of propagating waves – the average field and the field correlator – have been obtained at various proportions between the wavelength and the field correlation radius on the stochastic screen.     

激光入射孔径对柱形腔靶辐照不均匀度的影响

 研究了激光入射孔径对柱形腔靶中 l=2阶靶丸辐照不均匀度的影响，计算得到了激光入射孔径对辐照不均匀度随时间变化的影响可以用源于某一固定点的一族曲线来描述。此固定点是由与激光光斑的位置决定的，与腔靶的半径和入射激光束的入射角有关，而与激光入射孔径的大小无关。辐照不均匀度随时间的变化是由激光光斑的辐射温度的变化和腔壁辐射温度的变化决定的，激光入射孔半径的大小影响着辐照不均匀度随时间变化的曲线的梯度，入射孔越大，曲线的梯度就越大。激光入射孔对l=2阶靶丸辐照不均匀度的影响与入射孔半径近似呈线性关系。     

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在非对称磁镜场微波ECR等离子体中引入了磁电加热系统,研究了电极环大小、轴向位置以及双环加热对离子温度的影响.结果表明,大小合适的电极环能有效提高离子的加热温度,且最优电极环尺寸主要取决于离子回旋半径.电极环轴向位置的选择主要与磁镜场位形有关,将电极环置于磁镜场中部的弱磁场位置时最有利于离子温度的提高.采用双电极环加热能进一步提高离子温度,并且其加热效果是单环加热的两倍.     

微小孔衍射——近场光学理论

推导了圆孔衍射公式，该公式不受孔径大小和到屏距离的限制，可以作为近场光学的理论。它满足麦克斯韦方程标量形式和基尔霍夫边界条件，包括传播波和衰减波。数值计算表明，此结果优于用Ｂｅｔｈｅ模型所得到的近场理论的结果     

Analysis of the axial electric field in a plasma-loaded-helix travelling wave tube

A helix type slow wave structure filled with plasma is immersed in a strong longitudinal magnetic field. Taking into account the effect of the plasma and the dielectric, the system is separated radially into three regions. By means of the sheath model and Maxwell equation, the distribution of the electromagnetic field is established. Using the boundary conditions of each region, the dispersion relation of the slow wave structure is derived. The trend of change for the radial profile of the axial electric field is analysed respectively in different plasma densities, plasma column radius and dielectric constant by numerical computation. Some useful results are obtained on the basis of the discussion.     

Refined calibrations of the turbidity spectrum for ill-defined disperse systems

A corridor type of calibration curves of the turbidity-spectrum method is proposed for ill-defined disperse systems. It is found that the cubic-mean radius of particles strongly depends on factors to which optical instruments have a low sensitivity. The concept of an effective cubic-mean radius is introduced and an algorithm for constructing corridor calibration curves for this radius is given on the basis of the method of realistic (instrument-dependent) differentiation, which was proposed earlier. An example of a calibration curve for a relative refractive index of 1.12 is presented.     

Improving image quality in transcranial magnetic resonance guided focused ultrasound using a conductive screen

Transcranial Magnetic Resonance guided Focused Ultrasound (TcMRgFUS) has been proven to be an effective treatment for some neurological disorders such as essential and Parkinson's tremor. However, magnetic resonance guidance at 3 Tesla (3T) frequencies and using the large hemispherical transducers required for TcMRgFUS results in artifactual low-signal bands that pass through key regions of the brain. The purpose of this work was to investigate the use of a circular conductive Radio Frequency (RF) screen, that is bent to have a 12 cm radius in one direction and positioned near the top or back of the head, to reduce or remove these artifactual low-signal bands in TcMRgFUS.The impact of using an RF screen to remove these low signal bands was studied in both imaging experiments and electromagnetic simulations. Hydrophone measurements of the acoustic transparency of the bronze 2 mm diameter square mesh screen used in the imaging studies were compared with temperature measurements with and without the screen in heating studies in the TcMRgFUS system.The imaging and simulation studies both show that for the different screen configurations studied in this work, RF screen removes the low-signal bands and increases both homogeneity and signal-to-noise ratio (SNR) throughout the region of the brain. Hydrophone and heating studies indicate that even a 2 mm wire mesh provides minimal attenuation to the ultrasound beam. Simulation results also suggest that a 1 cm mesh will provide adequate artifact suppression with even less ultrasound attenuation.An RF screen that disrupts the natural waveguide nature of the transducer in the 3T MR environment can change the electromagnetic field profile to reduce unwanted artifacts and provide an imaging region which has more homogeneity and higher SNR throughout the brain.