衍射微柱透镜轴向光强分布特性的严格电磁分析

衍射聚焦器件轴向光强分布的焦深和焦移特性，直接决定着系统接收面的装配误差和获得最佳的能量利用率。当器件的口径和面型特征尺寸可与照射波长比拟时，必须考虑光波与衍射器件的电磁作用。利用严格电磁分析方法——时域有限差分法，对有限口径衍射微柱透镜的轴向光强分布进行了严格分析，并且与传统的标量分析方法进行详细比较。分析比较了TE和TM极化波入射情况下，不同面型分布(8台阶，16台阶量化面型和连续面型)的衍射微柱透镜焦深和焦移特性与透镜F数的关系。结果表明透镜轴向光强最大点向透镜面偏移，焦移量的严格计算结果要大于标量计算结果，表明透镜的快聚焦特性，而二者得到的焦深量基本一致，同时两种理论方法都表明透镜焦深和焦移随F数的增加而增加。     

大相对孔径变焦红外光学系统无热化设计

随环境温度变化红外镜头会产生热离焦现象,一般定焦红外光学系统可通过多种红外材料组合或引入衍射面来实现光学被动式无热化设计,而变焦红外光学系统大多是通过移动透镜组来实现机械主动式无热化设计。文中根据光学变焦原理和光学被动式无热化原理,提出一种变焦光学被动式无热化设计方法,并采用该方法设计了一种大相对孔径双视场无热化长波红外光学系统。该系统焦距为25/50 mm（变倍比为2:1）,工作波段为8~12 μm,F数为0.9,可匹配640×512,像元为17 μm×17 μm的非制冷红外焦平面阵列探测器。光学设计中采用3种红外光学材料（硫系玻璃HWS6、硒化锌和锗）组合,并引入3个偶次非球面,实现变焦无热化设计。设计结果表明:该系统在宽温度范围内具有良好的成像效果和温度自适应性,在空间频率30 lp/mm处,-50℃~80℃温度范围内各视场MTF均大于0.3。该红外光学系统结构简单、工艺良好,在红外车载领域有着广泛应用前景。     

温度气压对高分辨力光刻物镜像质影响研究

分析温度气压对物镜光学材料、透镜厚度间隔,以及空气折射率的影响,并用空气折射率对物镜像质影进行模拟计算。研究表明物镜焦面产生较大漂移,对僧率有一定影响,而对畸变影响较小,指出对物镜进行温度气压控制补偿是必要的。     

湍流大气对高斯光束聚焦特性的影响

基于广义惠更斯-菲涅尔原理,推导出高斯光束在湍流大气中经薄透镜聚焦后的光强解析表达式,进而得到轴上点最大光强和相对焦移的公式。对表达式进行的数值仿真结果表明,湍流大气中高斯光束的聚焦规律与自由空间中高斯光束的聚焦规律相同,湍流大气对高斯光束聚焦特性的影响表现为,使得轴上点最大光强减小、相对焦移增大。因此,为在探测器上获得最大光强和较小的相对焦移,应采用大束腰高斯光束通过短焦距透镜进行聚焦。     

基于反射式平行光管法的紫外透镜焦距测试研究

光学透镜是光学仪器中最基本的器件,而焦距又是光学透镜最重要的特性参数,如何精确测量透镜的焦距一直以来都是研究重点,然而目前鲜有针对紫外透镜焦距测试的研究。本文结合紫外透镜的特点,对一种基于反射式平行光管的紫外透镜焦距测试方法进行了研究,并以此设计出了一套紫外镜头焦距测量系统,同时选用了不同焦距的紫外镜头进行了实验,最后对系统进行了误差分析。实验结果表明,该测量系统可以对紫外镜头焦距进行高精度测量,25 mm镜头的测量误差为2.041%,100 mm镜头的测量误差为0.934%,验证了测量系统的准确性。     

Concentric-Ring and Sector-Vortex Phased-Array Applicators for Ultrasound Hyperthermia

Concentric-ring phased arrays subdivided into sectors (radial slices) can, with appropriate phasing, produce power absorption patterns useful for hyperthermia cancer therapy. The ability of a concentric-ring array to move a focal region along the central axis of the transducer is well known. Less well known is the ability of such an array to produce variable diameter annular (or ring) focal regions. Such focal rings can be effective in heating some tumors if directed around the tumor periphery. These focal rings have been produced in the past by fixed annular focus lenses, or effectively by mechanical scanning of "point" focus ultrasonic transducers. Production of these focal rings by a concentric-ring phased array has the advantage of allowing the focal ring diameter and focal length to be easily changed and scanned by phasing providing much greater heating flexibility. However, under some conditions such arrays produce very large secondary focus effects along the central axis of the amay. Concentric-ring arrays can also provide only patterns of circular symmetry. These problems can be partially solved by dividing the disk of the array into sectors. By appropriate phasing of the sectors, the intensity along the central axis can be greatly reduced. Moreover, appropriate phasing of the rings and sectors can produce patterns that are circularly asymmetric. By controlling these asymmetries, nonspherical tumors can be heated more optimally. Power absorption patterns in Iossy media for this class of applicators are analyzed numerically allowing a quantitative evaluation of both advantages and limitations of this approach. A thermal model based on the bioheat equation is also used to predict temperature distributions in volumes where important thermal parameters, particularly blood flow, are varied.     

大相对孔径宽光谱星敏感器光学镜头设计

为了提高星敏感器相对孔径,拓宽探测光谱范围,文中通过探测器灵敏度模型的计算,确定了星敏感器光学系统的设计参数,进而设计了一款基于卫星平台的星敏感器光学镜头。该镜头由7片球面透镜组成,光谱范围为500~800 nm,焦距为50 mm,相对孔径为1/1.25,视场角为8.458.45（对角线视场角为11.96）,总长83.33 mm。镜头采用像方远心光路,减小了因像面离焦及其他因素引起的测量误差。优化后的镜头畸变小于0.5%,质心色偏差控制在2 m内,能量集中度（33像元内）大于80%,最大倍率色差为-0.073 m,轴外视场的弥散斑能量集中度和轴上视场基本一致。对比不同温度下的光学系统,焦距变化量很小,验证了无热化设计要求,镜头的成像质量良好。     

硫系玻璃在民用红外车载成像系统中的应用

针对324256非制冷探测器,设计了一个工作波段为8~12 m,有效焦距为9 mm,F数为1.3,视场角为33.2626.28的红外车载镜头。镜头采用了硫系玻璃材料Ge28Sb12Se60制备的两片镜片,结合常规红外材料锗以及硫化锌材料制备其他两片镜片,通过合理分配各个镜片的光焦度达到系统整体无热化设计的效果。利用硫系玻璃易于精密模压制备非球面的特点,仅在一片硫系玻璃镜片上设计了一处非球面。设计结果表明该系统在-40~60 ℃的温度范围内具有良好的消色差/热差性能,且调制传递函数(MTF)接近衍射极限。     

红外双波段光学系统被动式消热差设计

为提高红外光学系统的目标探测识别能力,增强其温度适应能力,在分析红外材料在中波和长波红外波段的色差与热差特性的基础上,根据系统光焦度分配、双波段轴向消色差和双波段消热差等要求,利用红外色差图合理选择光学材料组合,设计了一款中波和长波红外双波段消热差系统,系统采用非制冷探测器,工作波段为3~5 m和8~12 m,由4片透镜组成,焦距为50 mm,相对空间为1:1.25,全视场角为14,总长67.9 mm。设计结果表明:在温度范围-50~60 ℃范围内,在空间频率为17 lp/mm处,系统在中波和长波波段的MTF值均大于0.4,表明系统有较强的温度适应性。     

可见-近红外无热化连续变焦光学系统设计

变焦系统中，动组间相对位置的变化会导致各镜组的初级像差特性发生变化，环境温度的变化还会导致各焦距位置热差的改变，给无热化连续变焦系统的设计造成较大困难。针对该问题，从光学系统像差模型出发，将变焦系统像差分为定组像差、动组内像差和动组间像差三类，并结合变焦系统的消色差和消热差模型，讨论了无热化连续变焦光学系统的设计原则，及变焦系统设计中各组元的光焦度分配和材料选用方法，给出了一个宽波段连续变焦光学系统设计实例，该系统F数为5、焦距范围为8~120 mm、焦面对角线长6.2 mm、波长范围为0.48~0.68 μm和0.7~0.9 μm。所述系统仅采用了七种普通光学玻璃材料，透镜总数12组16片，总长仅90 mm，在?40~60 ℃范围内，变焦全程均具有较好的成像质量和公差特性。     

Focusing characteristics of curvilinear half-open Fresnel zone plate lenses: plane wave illumination

A diffraction field-focusing equation based on a specific conical-segment linearization procedure is derived for the Fresnel zone plate (FZP) lens of arbitrary curved profile and is applied for contrasting plane, spherical, parabolic and conical zone plate lenses, convex-side illuminated by a paraxial plane wave front. Two sets of 100-GHz curvilinear and plane FZP lenses are studied numerically with regards to their dimensions, axial focusing intensity and footprint, and frequency bandwidth. For the first set , where the curvilinear and plane lenses share a common lens base aperture and have equal focal lengths, the following new finding has resulted: regardless of their different in shape profiles the FZP lenses have equal zone numbers and produce similar axial focusing. The second set also consists of plane, spherical, parabolic and conical lenses. They share a common apex, and have equal in diameter base apertures and focal lengths but different thicknesses. For such disposition and proportions, the FZP lenses possess different zone numbers and focusing parameters (gain, efficiency, footprint and bandwidth). The belief that the curvilinear FZP have superior (or inferior) electromagnetic characteristics, compared to those of the plane FZP lens with equal number of zones is not in general true. Their relative focusing qualities can vary significantly depending on the lens positioning and dimensions.     

高斯光束通过两种球差透镜的聚焦特性比较

通过研究,比较了高斯光束通过两种不同球差透镜的聚焦特性。研究表明,高斯光束通过球差透镜的聚焦特性由球差透镜的类型、球差大小和光束的菲涅耳数共同决定。不同的球差透镜要实现无焦移聚焦和越过焦点的聚焦的条件是不同的。     

基于二元衍射面的长波无热化光学系统设计

仅用3片透镜,设计了一款匹配640×512氧化钒非制冷长波焦平面探测器的红外系统。该系统焦距为100 mm,F数为1.1,总长为107 mm,工作波段范围为8~12μm,引入一片二元衍射面实现无热化温度补偿功能。利用ZEMAX进行仿真设计,结果表明:在-40℃^+60℃温度范围内,系统奈奎斯特频率(30lp/mm)处MTF均达到0.49,接近衍射极限。该系统具有焦距较长,相对孔径大、全视场像质优良、温度适应良好、二元面衍射效率高、易于加工和结构紧凑的特点。     

基于模板匹配的莫尔条纹倾角计算

提出了一种基于模板匹配的亚像素处理方法,可以精确计算出在大口径长焦距测量过程中出现的莫尔条纹的角度。基于泰伯效应和莫尔条纹干涉的长焦距测量方法是一种高精度的焦距测量方法。理论分析表明:这种测量方法的精度很大程度上依赖于莫尔条纹角度的精度。之前是通过迭代算法在亚像素域中寻找莫尔条纹频谱的最大值点来计算莫尔条纹的角度。然而实验过程中得到的莫尔条纹往往会出现不同程度的弯曲和畸形,这会大大影响这种方法的测量精度。从改进测算角度算法这个角度出发,针对傅里叶变换后的频谱图,基于模板匹配的思想,对各种莫尔条纹进行二维正态分布拟合,找出频谱点精确坐标,从而精确测量莫尔条纹角度。理论分析和软件仿真表明:这种方法具有高精度、高稳定等优点,能有效提高长焦距的测量精度。     

紧凑型大变倍比红外光学系统设计

针对常用变焦结构在实现大变倍连续变焦时存在的各类问题,从变焦系统设计的基本理论出发,提出了一种可用于大变比光学系统设计的两级串联变倍模型,给出了相应的变焦方程及凸轮曲线设计的优化控制条件和方法。该模型由两组元连续变焦前组和具有变倍放大功能的二次成像后组串联组成,通过移动前组中的变倍组与补偿组实现一级变倍;通过移动补偿组与二次成像组中的二级变倍组,对前组焦距进行二级放大,扩大整个成像系统的变倍能力,同时,二次成像组还压缩了物镜口径,保证了冷阑匹配。完成了一个大变比连续变焦光学系统设计,该系统工作波段为3.7~4.8 m,采用640480制冷型面阵探测器,像元大小15 m,F数恒定为4,可以实现6.5~455 mm、水平视角0.92~58.2、达70倍的连续变焦功能,仅采用了两种材料,十片透镜,总长300 mm,具有优良的成像质量和公差特性。     

Study on passive compensation of temperature induced thermal lenses

The thermal lens problem of optical system caused by high temperature environment is a common problem. Athermal design of lenses based on optical calculation software is an effective passive compensation method. But it is difficult to determine its accuracy and measure it experimentally. We describe an athermal design technology and propose a simulated scheme to verify the accuracy of this design. Three materials with negative dn/dT have been selected to compensate for the thermal lenses produced by a fused silica lens. The results show that the compensation effect of N-PSK53A is the best.     

Multifocal three-dimensional bootlace lenses

It is well known that a two-dimensional (parallel plate configuration) bootlace lens can be designed to have more than one focal point. Wide angle scanning capabilities of these lenses in two dimensions is well established, being larger for higher number of focal points. However, no three-dimensional bootlace lens having more than one focal point has been reported. It is the purpose of this paper to report on three-dimensional bootlace lenses having two, three, and four perfect focal points. Equations for lens surfaces are obtained for all three cases. The results of the aperture phase error analysis show that a lens with a larger number of focal points can be scanned to much larger angles in one plane at the expense of the scanning capability in the orthogonal plane.     

航空相机焦面组件相变温控设计及验证

航空相机焦面组件是机载电子设备中具有严格温度要求的重要组件,其工作期间温度过高产生的热噪声和暗电流将导致成像质量下降。讨论分析了某型航空相机焦面组件热设计的特点,采用封装有相变材料的相变温控系统进行散热,根据结构特点和导热路径,给出了热设计方案。采用有限元数值分析方法,建立了热平衡方程和热分析计算模型,应用热分析软件IDEAS-TMG在给定温度边界条件下进行瞬态仿真分析,给出了组件的热响应性能。热分析结果表明:焦面组件和散热器工作温度范围分别为18～31.1 ℃、18～28.2 ℃。所获得的分析结果能够满足热控指标要求。最后通过热实验对采用相变温控系统的热设计方案进行了验证,验证实验结果与数值分析结果吻合较好,结果对比最大偏差均不超过5%,验证了数值分析的正确性和温度预示的有效性。实验过程中焦面组件和散热器工作温度范围分别为18～32.3 ℃、18～29.6 ℃。     

折/衍射双波段共光路齐焦光学系统设计

为了提高双波段光学系统成像性能,结合可见光和中波红外的特点,设计了无光路补偿的折/衍射双波段共光路齐焦光学系统。对系统的4片透镜波段间消色差以及焦距补偿表达式进行了推导,采用4片透镜并引入二元衍射面,通过合理匹配光学系统光焦度,实现了系统共用一组光路,在可见光和中波红外两个波段的焦距一致,提高了双波段观测目标信息的一致性。设计的双波段共口径/共光路成像光学系统的工作波长为0.38~0.76 m,3~5 m,系统的焦距为90 mm,视场角为0.5,F数为3,在-40~+60℃的温度范围内采用光学被动式进行消热差设计。设计结果表明:系统结构简单,体积小,成像质量接近衍射极限。