失调三反消像散光学系统像差特性

文中以矢量波像差理论为基础,对TMA 光学系统的失调像像差特性进行分析,通过分析发现失调TMA 系统的初级球差在全视场内为常量,彗差在全视场内的方向与量值均为常量,由失调引入的像散表现为失对称性、像散值与视场成线性,其零点位于中心视场。在校正失调产生彗差时,TMA 系统像散零点位于轴上视场,像差接近于零,而边缘视场的像散依然较大,因此在TMA 系统的装调过程中,需要测量多个视场的波像差。在同样情况下若轴上视场测量到像散,则是由于主镜的面形误差导致而非系统失调引起。利用CODE V对失调TMA系统的失调像差分布进行仿真,结果表明,利用矢量波像差理论可以对失调TMA系统的像差进行定性分析,以提高TMA 系统的装调效率。     

几种失调反射光学系统的波像差特性

为了描述失调状态下反射光学系统在整个像平面中的波像差分布特性,从而对反射光学系统进行有效的装调,对偏心和倾斜影响下的几种反射光学系统的三阶彗差和三阶像散进行了研究。首先,对失调光学系统三阶波像差的矢量形式进行了推导。然后,对失调状态下经典Cassegrain系统、Ritchey-Chrtien系统和三反射镜消像散系统三阶彗差和三阶像散的分布情况进行了分析,并且对两反射和三反射系统的装调进行了简要的讨论。使用Zernike多项式对视场中各个位置的波像差进行拟合,分离出三阶彗差和三阶像散并进行了全视场显示。理论分析与实际拟合结果一致,说明结论是正确的。     

离轴反射光学系统像差特性研究

以轴对称光学系统的初级矢量波像差理论为基础,通过引入孔径缩放因子和孔径偏移矢量,获得了离轴反射光学系统初级像差特性。通过分析可知:离轴反射光学系统的初级像差依然由球差、彗差、像散组成。由于孔径缩放因子存在,离轴反射光学系统的波像差系数均有不同比例的减小,且轴对称光学系统的高级孔径像差会在对应离轴光学系统中引入较低阶孔径像差,例如轴对称光学系统未校正球差,对应的离轴光学系统除过球差外还将引入彗差、像散等。相比于轴对称光学系统的像差,由于孔径偏移矢量的引入,离轴反射光学系统的像差不再关于中心视场旋转对称,有可能在轴外视场产生像差零点。     

一种改进型的红外卡塞格林光学系统设计

在卡塞格林光学系统的设计中引入曼金反射镜、中继镜组,以提高卡塞格林光学系统承担视场和相对孔径的能力.通过设计实例表明,这种改进后的卡塞格林系统承担视场、相对孔径的能力得以很大提高,像质、结构长度满足设计的要求.     

基于衍射光学的大视场卡塞格林光学系统设计

为了改善卡塞格林光学系统的视场,将衍射透镜成功地引入大视场卡塞格林光学系统的设计中,并给出了设计方案.该系统在次镜后使用了2个校正透镜,且第1个透镜的前表面具有衍射面,能在3.6°视场内获得接近衍射极限的成像质量,各视场的波前差均小于1/4波长,光学传递函数(MTF)接近衍射极限.设计结果表明,衍射光学元件(DOE)对于改善卡塞格林系统的视场具有重要的作用,此设计方案降低了对加工工艺的要求,大大降低了成本,结构紧凑且具有良好的消像差特性.     

基于像差特性分析的光学系统横向失调校正方法

在高分辨力光学系统中,光学元件偏心引起的光学系统初级像差特性已经成为系统设计和装调必须要考虑的因素,文中拟从分析透镜横向失调量对像差影响的基础上,提出了一种考虑像差特性影响的光学零件装调校正方法。在考虑光学元件偏心对像差的影响的情况下,推导了光瞳中心位置和像面中心位置随透镜偏心程度的变化,建立了光学系统失调校正量和像差增量之间的数学关系,提出了一种基于像差理论的透射式光学系统横向失调校正方法,可以弥补现有高斯光学校正方法的不足。以三透镜准直系统为例,利用ZEMAX软件仿真验证了文中方法的有效性,实验表明该方法所选择的调整方案在所有调整方案中引起的像差增量最小,降低了校正过程中对光学系统成像质量的影响。     

含衍射透镜的卡塞格林红外光学系统设计

该设计将衍射透镜引入到卡塞格林红外光学系统中。设计结果表明,衍射透镜的引入增大了卡塞格林光学系统的视场和相对孔径,改善了成像质量;同时也降低了加工工艺的要求,大大节约了成本。     

基于卡塞格林系统的激光测距接收光学系统的设计

针对远程激光测距系统的轻量化、小型化需求,采用了大口径卡塞格林物镜光学系统,达到了用较小的发射功率实现较远的目的,同时加入了与视场匹配的视场光阑,来抑制杂散光对探测能力的影响。通过合理优化布局,平衡系统横向尺寸与主次镜遮挡比需求,最终采用了8×望远系统与大相对孔径的聚焦系统组合的结构方式,优化后的系统成像质量好,结构紧凑,重量轻,满足实际应用需求。     

经典卡塞格林系统热差分析

对纯反射的经典卡塞系统,推导出了热差的数学解析式,用解析式分析计算了三种典型情形,并同步用ZEMAX软件进行了模拟演算。结果表明：当材料选择不当时,将会产生很大的热差;当反射镜材料和结构件材料的膨胀系数值相同时,热差恒为零。     

薄膜诱导波前像差

用于望远镜反射镜或其他光学表面的膜层会对光学系统的成像质量产生重要影响。本文计算了由膜层对S、P分量的相移而引起的像散和离焦。薄膜诱导波前像差通常是可以忽略的，但在某些情况下会超过系统的几何波前像差。本文以F数为f／1．5的卡塞格林望远系统中所用反射增强型薄膜的诱导波前像差为例进行了数值分析。     

卡塞格伦光学天线光传输特性研究

对卡塞格伦光学天线光传输特性进行了理论分析,重点研究了影响光学天线光传输质量的几个重要因素,并进行了测试结果与仿真验证。为实际研究大气激光通信系统中光学天线的光传输特性提供了理论依据,具有重要的实用价值。     

Magnetic fluid based deformable mirror for aberration correction of liquid telescope

A magnetic fluid based deformable mirror (MFDM) that could produce a large stroke more than 100 μm is designed and demonstrated experimentally with respect to the characteristics of the aberration of the liquid telescope. Its aberration correction performance is verified by the co-simulation using COMSOL and MATLAB. Furthermore, the stroke performance of the MFDM and the decentralized linear quadratic Gaussian (LQG) mirror surface control approach are experimentally evaluated with a prototype of MFDM in an adaptive optics system to show its potential application for the large aberration correction of liquid telescopes.     

Measurement of air pollutants by differential optical absorption spectroscopy using a Cassegrain telescope with fibers

A differential optical absorption spectroscopy (DOAS) method is presented and used for the air pollutant detection. The novel measurement frame employs a Cassegrain telescope and a combined fiber bundle. The emitting and receiving fibers are bundled together at one port. The common port is placed at the focus of the Cassegrain telescope. The total length of the prototype is reduced to about 1/2 of the traditional one. Air pollutants of SO2, NO2 and O3 are monitored by the prototype, and the concentrations are inverted. Results show that the correlation coefficients are 0.9490, 0.9614 and 0.9301, respectively. And there is a good consistency between the measured results and the reference data.     

自聚焦棒透镜准直系统的装配误差引起的附加耦合损耗分析

一对１／４节距自聚焦棒透镜构成的准直系统通常存在三种装配误差：错位、间隔和倾斜,由此产生一定的附加耦合损耗。理论分析和数值计算结果表明,损耗与装配误差在小范围内近似呈平方递增关系,增幅与透镜聚焦参数有关。根据具体装配工艺选取合适的自聚焦棒透镜,能显著降低耦合损耗。     

Surface accuracy of Cassegrain antennas

For a Cassegrain antenna system, a simple and general procedure is presented for computing the effective surface root mean square (rms) and beam deviations considering primary surface distortions and relative translations and rotations of the antenna components. It is shown that certain primary reflector distortions can be compensated for by an appropriate adjustment of the subreflector position. Different methods in use for calculating surface rms are reviewed. It is shown that the method in which the deformed configuration of the primary reflector is best fitted with another paraboloid yields a surface rms almost equal to that obtained by the optimal positioning of the antenna components. The actual deformation patterns of several large Cassegrain antenna systems with different structural concepts are reviewed. It is shown that for a class of antenna structures, the gain can be significantly improved by an optimal positioning of the subreflector.     

卡塞格林系统的杂散辐射分析

卡塞格林系统是一种常见的同轴反射系统,具有长焦距、大通光口径、工作波段宽的特点。但是,卡塞格林系统的结构形式,决定了其受杂散辐射的严重影响。本文对卡塞格林系统进行了杂散辐射特性的研究和讨论,首先指出了该系统的杂散辐射源,并在杂散光分析软件TracePro中建立了系统的光机模型,对系统进行杂散光追迹。然后分析得出系统的外部杂散辐射和内部杂散辐射对系统的影响,得到系统的点源透过率,并据此指标评价系统的杂散光抑制水平。最后,针对系统的杂散辐射,设计了遮光罩并提出其他杂散防护措施。     

Design of a dichroic Cassegrain subreflector

The design of a dichroic subreflector for a dual-frequency reflector antenna is described. This antenna consists of aKu-band Cassegrain feed requiring the subreflector surface to be highly reflective at 13-15 GHz and a primary focusS-band feed requiring the subreflector to be transparent at 2.0-2.3 GHz. Such a performance is achieved by a surface of crossed dipoles printed on a dielectric sheet. The influence of parameters, dipole length, width and spacing, and the dielectric constant and thickness of the sheet on the reflection and transmission coefficients is experimentally evaluated. An analysis based upon the Floquent mode theory is shown to correctly predict the experimental results. The construction of a hyperbolic subreflector using the selected surface parameters is briefly described. As compared to a solid subreflector of identical shape, this dichroic subreflector produced a negligible loss (less than 0.1 dB) over a 13-15 GHz band. At theSband the loss was less than 0.2 dB over narrow selected bands and the axial ratio deterioration was also no more than 0.2 dB.     

Broad-band VSWR measurements of a Cassegrain antenna

Broadband VSWR measurements are reported on a smallF-number Cassegrain antenna. Cyclical variations of VSWR between 1.00 and 1.25 with a 350-MHz frequency interval between unity VSWR values were observed over the 8.5-12.4 GHz frequency range. These variations correspond to a change in the power transmission ratio of 1.231 percent between the unity and 1.25 values of VSWR.