星体目标自适应光学成象补偿

大气湍流等动态波前扰动限制大型望远镜的分辨能力，是从有望远镜以来几百年的老问题，自适应学技术提供了解这一问题的途径。但对星体目标来说由于所能利用的光能极为有限，动态扰动的时间－空间特性又对系统提出很高要求，因而难度很大。本文报导我们用２１单元自适应光学系统在云南天文台１．２ｍ望远镜上对星体目标进行的首次试验。介绍了针对弱光动态目标的特点对系统的改进。实验结果表明了这一自适应光学系统可以在光子计数率     

Optical performance of the 6.5-m off-axis new planetary telescope

We describe an off-axis design for a 6.5-m astronomical telescope optimized for low scattered light and low emissivity. This is part of a new concept for an instrument that we call the New Planetary Telescope. We show how the geometric optical performance can equal that of an on-axis conventional telescope while the diffractive performance fundamentally surpasses conventional telescopes because of the absence of pupil obstruction. The decentered concept also allows wide-field and versatile instrumentation configurations that are not possible with more-conventional designs.     

Optical Performance of Large Ground-based Telescopes

Abstract

Images taken with ground-based telescopes are dominated by atmospheric seeing. Analytical expressions of long-exposure optical functions, namely the modulation transfer function, point spread function and encircled energy are established, under the assumption that dome and telescope seeing are brought to negligible values, and that the diameter of the telescope is larger than the atmospheric coherence length. The influence of guiding errors and axisymmetrical telescope aberrations is also assessed, and a definition of optical quality is proposed. The results are generalized and the optical performance of a ground-based telescope is expressed in terms of effective diameter and signal-to-noise ratio.     

The Diffuse Interstellar Cloud Experiment: a high-resolution far-ultraviolet spectrograph

We have designed, assembled, and launched a sounding rocket payload to perform high-resolution far-ultraviolet spectroscopy. The instrument is functionally a Cassegrain telescope followed by a modified Rowland spectrograph. The spectrograph was designed to achieve a resolving power (R=λ/δλ) of 60,000 in a compact package by adding a magnifying secondary optic. This is enabled by using a holographically ruled grating to minimize aberrations induced by the second optic. We designed the instrument to observe two stars on opposing sides of a nearby hot/cold gas interface. Obtaining spectra of the O VI doublet in absorption toward these stars can provide new insight into the processes governing hot gas in the local interstellar medium. Here we present the optical design and alignment of the telescope and spectrograph, as well as flight results.     

望远镜光学结构对自适应光学校正能力的影响分析

自适应光学系统在高分辨力成像望远镜中发挥了重要作用。自适应光学系统对于望远镜系统中的低阶像差几乎可以完全校正,但是会牺牲变形镜的校正行程量;对于中高阶像差,自适应光学系统不能完全校正,如何减小高阶残余误差是望远镜系统设计需要考虑的问题之一。本文首先分析了望远镜光学结构中的主镜结构、次镜遮拦、次镜支撑筋、主次镜装调和光学加工等静态和准静态像差情况,然后分析了这些因素如何影响自适应光学校正能力,最后给出了对望远镜光学结构的要求。     

光学综合口径望远镜设计方案讨论

本文提出新建一台4.3米光学、红外新技术望远镜。并与现有北台的几台望远镜用光纤联机提高集光能力达5.1米口径。将4.3米与2.16米望远镜用真空管道联机集像作CCD照相和光干涉测量,提高分辨率达10余米口径。     

Super high resolution for long-range imaging

A new optical system with a resolution that is superior to the resolution of the usual optical systems with diffraction limit is presented. We introduce a newly generated narrow light beam that propagates for a long range while almost maintaining its beam width and show that the beam width is narrower than that of the diffraction limit of normal optics. Thus a super high resolution is achieved for a long range, e.g., a range of a few kilometers, by the use of a 10-cm-diameter telescope. The high resolution for long-range imaging can be obtained by a Galilean telescope with a negative eyepiece that has a spherical aberration. We demonstrate theoretically high-resolution imaging by using simple objects and assuming a telescope 10 cm in diameter and a visible wavelength. A comparison of simulation results by the conventional optical system and by the special optical system clearly shows the superiority of the new system.     

Optical design of the atacama cosmology telescope and the millimeter bolometric array camera

The Atacama Cosmology Telescope is a 6 m telescope designed to map the cosmic microwave background simultaneously at 145, 215, and 280 GHz with arcminute resolution. Each frequency will have a 32 by 32 element focal plane array of transition edge sensor bolometers. The telescope and the cold reimaging optics are optimized for millimeter-wave observations with these sensitive detectors. The design of each is described.     

Characterization of the supermirror hard-x-ray telescope for the InFOCmuS balloon experiment

A hard-x-ray telescope is successfully produced for balloon observations by making use of depth-graded multilayers, or so-called supermirrors, with platinum-carbon (Pt/C) layer pairs. It consists of four quadrant units assembled in an optical configuration with a diameter of 40 cm and a focal length of 8 m. Each quadrant is made of 510 pieces of coaxially and confocally aligned supermirrors that significantly enhance the sensitivity in an energy range of 20-40 keV. The configuration of the telescope is similar to the x-ray telescope onboard Astro-E, but with a longer focal length. The reflectivity of supermirrors is of the order of 40% in the energy range concerned at a grazing angle of 0.2 deg. The effective area of a fully assembled telescope is 50 cm2 at 30 keV. The angular resolution is 2.37 arc min at half-power diameter 8.0 keV. The field of view is 12.6 arc min in the hard-x-ray region, depending somewhat on x-ray energies. We discuss these characteristics, taking into account the figure errors of reflectors and their optical alignment in the telescope assembly. This hard-x-ray telescope is unanimously afforded in the International Focusing Optics Collaboration for muCrab Sensitivity balloon experiment.     

Special configuration of a very large Schmidt telescope for extensive astronomical spectroscopic observation

A special reflecting Schmidt telescope is used to observe celestial objects. The telescope has an aperture of 4m, f ratio of 5, and a 5° field of view. Its optical axis is fixed and tilted 25° to the horizontal that runs from south to north. The celestial objects were observed for 1.5 h as they passed through the meridian. The shape of the reflecting Schmidt plate has to be changed with each different declination δ and in the tracking process. This is achieved with active optics. The sky area to be observed is -10° ≤ δ ≤ +90°. There are plans to place ~4000 optical fibers on the telescope focal surface that will lead to a dozen spectrographs.     

Wide-field Fizeau imaging telescope: experimental results

A nine-aperture, wide-field Fizeau imaging telescope has been built at the Lockheed-Martin Advanced Technology Center. The telescope consists of nine, 125 mm diameter collector telescopes coherently phased and combined to form a diffraction-limited image with a resolution that is consistent with the 610 mm diameter of the telescope. The phased field of view of the array is 1 murad. The measured rms wavefront error is 0.08 waves rms at 635 nm. The telescope is actively controlled to correct for tilt and phasing errors. The control sensing technique is the method known as phase diversity, which extracts wavefront information from a pair of focused and defocused images. The optical design of the telescope and typical performance results are described.     

空间引力波探测望远镜多自由度形变测量方法解耦研究与噪声分析

空间引力波探测望远镜是引力波探测卫星的核心载荷之一,它同时对传输光束进行扩束和缩束。光程稳定性是望远镜的核心指标之一,其与望远镜结构稳定性密切相关。为了满足引力波探测任务对望远镜提出的超高光程稳定性和结构稳定性要求,必须对望远镜结构形变测量进行研究。本文开展了对空间引力波探测望远镜多自由度形变测量的研究,重点解决多自由度测量的耦合问题,并对误差来源进行详细分析。在空间引力波探测望远镜的研制阶段,该测量方法的研究有望满足望远镜多自由度形变测量的需求,为望远镜设计提供多自由度形变的数据反馈,为望远镜光程稳定性研究提供指导。

     

Step-zoom dual-field-of-view infrared telescope

The design of a dual-field-of-view telescope for an 8-12-microm imaging waveband is described. Preliminary calculations are made to determine the first-order parameters of the narrow- and the wide-field modes. To achieve a switchable dual-field-of-view system, one use an optical configuration based on the axial motion of a single lens group along the optical axis. The same lens is also used for focusing at near objects and for athermalization by small axial movement. A total of six lenses with one conic surface are used in the design, making the telescope cost effective and lightweight. The final optical design is presented, along with the aberrations curves and modulation transfer function plots, showing excellent performance in both fields of view.     

二元光学折/衍混合消色差望远物镜设计

首先从光栅衍射理论出发导出衍射光学元件的色散公式，并进一步推导出用一种材料进行折／衍混合消色差望远物镜设计的公式。最后给出全折射型、一个混合型消色差和一个改进型消色差望远物镜的例子，并进行了比较。结果说明，混合型透镜的性能优于全折射型透镜，而改进型消色差物镜的总体性能优于原混合消色差物镜     

云南天文台1.2m望远镜的光学系统

云南天文台 1 .2 m地平式望远镜目前进行着两种天文光学工作 :在国家地震监测网络中心内的人造卫星激光测距站的建立及常规观测 ;国家高技术 86 3的 6 1单元自适应光学系统的建立。对望远镜光学系统和两类天文光学工作给予了介绍。     

Cryogenic optical performance of the ASTRO-F SiC telescope

The lightweight cryogenic telescope on board the Japanese infrared astronomical satellite, ASTRO-F, which is scheduled to be launched early in 2006, forms an F/6 Ritchey-Chretien system with a primary mirror of 710 mm in diameter. The mirrors of the ASTRO-F telescope are made of sandwich-type silicon carbide (SiC) material, comprising a porous core and a chemical-vapor-deposited coat of SiC on the surface. To estimate the optical performance of the flight model telescope, the telescope assembly was tested at cryogenic temperatures, the total wavefront errors of which were measured by an interferometer from outside a liquid-helium chamber. As a result, the wavefront error obtained at 9 K shows that the imaging performance of the ASTRO-F telescope is diffraction limited at a wavelength of 6.2 microm, which is a little worse than our original goal of diffraction-limited performance at 5.0 microm.     

Variant of the anastigmatic telescope with three mirrors for back focal length

In this paper, an optical design is presented for an anastigmatic telescope with back focal length corrected with exact ray tracing to eliminate spherical, coma, and astigmatism aberrations. The telescope is formed of three conical mirrors, two of them polished on the same substratum. The optical design is divided into three stages: we began the design obtaining the Gaussian parameters in a first-order solution; posteriorly, were obtained analytically the three mirrors' asphericity in a third-order design. The final design stage consists of the implementation of the Fermat's principle, the Abbe sine condition, and the Coddington equations for the exact correction for the three aforementioned aberrations.     

Field-of-view limitations of phased telescope arrays

The optical performance of imaging phased telescope arrays is degraded by various design, manufacturing, and operational errors. Perhaps the most basic and fundamental of these error sources are the residual aberrations of the optical design chosen for the individual telescopes. We show that third-order field curvature and distortion, which are rather benign aberrations in a conventional telescope, result in relative phase and tilt errors between the individual telescopes making up the array. The field-dependent image degradation caused by these relative phase and tilt errors is then predicted for different subaperture configurations and telescope design parameters. For phased arrays made up of simple two-mirror telescopes, distortion limits the field of view to less than 5 arcmin for small subapertures (D < 0.5 m), and field curvature limits the field of view to less than 1 arcmin for subaperture diameters greater than 2 m. Quantitative parametric results yielding tolerances for residual field curvature as the phased array is scaled up in size are presented graphically. If a 0.5-deg field of view is desired for telescope diameters greater than 2 m, complex telescope configurations are necessary to satisfy the rather tight tolerances on both field curvature and distortion.     

望远镜光程稳定性测量方案设计及噪声理论分析

空间引力波探测对望远镜提出了高稳定性要求。为实现望远镜光程稳定性精度的独立测量与标定,开展了相应测量方法的研究。基于外差干涉测量原理,设计了高共模抑制干涉测量方案,建立了光程噪声理论模型。根据1 pm/Hz^1/2@1 mHz光程稳定性指标需求,分配测量系统组成部分光程噪声水平。为验证方案的可行性和噪声理论模型的准确性,搭建了望远镜前端干涉测量系统。根据实验仪器及光学组件相关参数,理论评估系统光程噪声水平为7.319 nm/Hz^1/2@10 mHz,与实验测量结果3 nm/Hz^1/2@10 mHz基本一致,表明干涉光路具有较好的噪声共模抑制特性,验证了噪声理论模型的准确性。当测试环境及仪器精度满足光程噪声指标分配要求时,该测量方案有望实现引力波望远镜光程稳定性测量。