波前传感器子孔径数和信标亮度的匹配

针对云南天文台１．２ｍ望远镜上的６１单元高分辨率自自应光学系统，进行了微光工作环境下波前传感器子孔径数和信标亮度匹配的实验研究。在Ｈａｒｔｍａｎｎ－Ｓｈａｃｋ波前传感器前的平行光路加入一个变倍光学系统，进行了８＊８、６＊６、４＊４和２＊２子孔径阵列在不同信标亮下波前感器对波前的探测实验。     

基于MEMS技术的自适应光学系统的研究

用自适应光学系统来校正由大气湍流等产生的波前畸变,能够得到很好的效果.通过对自适应光学系统的工作原理进行研究,提出了一种基于MEMS技术的微小型自适应光学系统校正波前畸变的方法,将MEMS技术应用于变形反射镜,并构建了具体的实验平台,用来校正一种人为产生的波前畸变,且阐述了具体的实验过程.实验结果表明,基于MEMS技术的自适应光学系统能够很好地闭环校正波前畸变,且其体积小、质量轻、校正性能稳定,为自适应光学技术在星载相机上的应用提供了依据.     

自适应光学在空间光学遥感器上的应用

阐述了在空间光学遥感器上应用自适应光学技术的必要性,介绍了国外的ＳＴ－ＭＴ,ＬＤＲ和Ｈｕｂｂｌｅ等几种空间光学遥感器应用自适应光学技术的情况,论述了轻小型和集成化的星载自适应光学系统的技术现状和发展趋势。进行了星载相机主镜温度变形的自适应光学校正实验,改善系数大于１０。这说明,对大口径、高分辨率空间相机采用自适应光学技术校正主镜由于温度场变化而产生的变莆,可以有效地改善波前质量。     

六自由度头部跟踪系统的误差修正

建立基于CCD图像处理的六自由度头部跟踪系统,对测量所得六自由度参量进行误差分析,发现误差主要由信标精度和六自由度之间互相依赖所造成.为降低由信标精度引起的初始误差,提出了系统初始误差修正方案,在初始状态下将各自由度归零,无须加工高精度的信标解决了系统初始误差问题.此外,提出各自由度参量独立提取方案,降低各参量之间的依赖程度,避免误差在各参量之间传递.实验结果表明,经过误差修正和算法改进后,六自由度的测量误差大大降低.在-30℃～30°的方位角变化范围内,方位角a的标准差为0.94°,横滚角β和俯仰角γ在0°位置标准差分别为0.30°和0.02°,位置X0和Y0在0 cm位置标准差分别为0.94 cm和0.01 cm,位置Zo在112.31 cm位置标准差为0.28 cm.     

用功率谱密度函数评价光学面形中频误差特性

采用二维ＰＳＤ功率谱密度函数来评价光学元件面形中频波前．而这部分波前误差在传统的分析中被表示为"残余量"．它们产生的散射会严重地影响光学系统的成象质量。简要叙述了ＰＳＤ的计算方法及实验结果。     

基于部分岭估计的Zernike模式法人眼波前像差重建

为了提高自适应光学系统中人眼波前像差的重建精度,进而提高自适应光学图像中的点扩散函数重建精度,提出了一种基于部分岭估计的Zernike模式前重建算法。首先,基于Zernike模式波前重建模型,分析了常用的模式系数求解方法;其次,在最小均方误差意义下,将部分岭估计的概念引入到自适应光学系统的波前重建算法中,通过确定最优岭估计参数来改善最小二乘估计的奇异性,从而抑制波前探测中测量误差的进一步被放大;最后,讨论了在波前斜率误差的影响下由两种算法所产生的误差大小。仿真实验结果表明：在波前重建算法中引入部分岭估计可有效减小模式系数的均方误差,相对于奇异值分解法减小了8%~10%,在波前探测测量误差增大的情况下,部分岭估计的波前重建精度要高于最小二乘估计法,有利于自适应光学后期中基于波前探测的图像复原研究。     

星敏感器参数标定及误差补偿

针对CCD星敏感器光学系统存在焦距不准确、CCD平面倾斜和旋转及光学镜头畸变等误差因素,在理想针孔模型的基础上,用几何方法建立了星敏感器模型。利用地面实验数据,以最小二乘法解算该数学模型,求出焦距、CCD平面倾斜和旋转因子及畸变因子等待标定参数。将标定出的参数代回数学模型,便可由星象点测量坐标直接计算并修正入射光方向矢量,从而对光学系统的误差进行了补偿。计算结果表明:星对角距统计偏差由标定前41″降到了17″,提高了计算精度。     

深空光通信中导航星表的构造

提出一种导航星表的构建方法，该方法以星跟踪器视场内最亮恒星作为信标，把信标锁定在视场中心，测量视场内其他恒星到信标的角间隔，把测量的所有恒星角间隔和信标的赤经、赤纬存储到导航星表中。基于该方法，利用史密森天文观测台恒星星表（SAO），选择星等小于6等的恒星，建立起导航星表，该星表仅包括5103颗星，其容量仅为1.2兆。相对三角形算法，该星表容量更小，可节省星载系统的存储空间，减少识别时间，提高跟踪速率。蒙特-卡诺仿真结果表明，利用该导航星表识别信标具有较好的抗干扰性，且当星跟踪器测角误差（30σ）在1μrad以内时，信标正确识别概率几乎为100％。     

提高线阵CCD拼接精度的研究

为了满足空间相机和其它监控、侦察相机高分辨率和宽收容度的要求,目前采用了多片CCD光学拼接技术.本文给出了线阵CCD的拼接模型,说明了CCD光学拼接的原理和方法.强调了拼接前对单片CCD物理特性和几何特性测量和挑选的重要性,以及在此基础上所采用的能显著提高拼接精度的误差压缩和误差分离的拼接方法.     

基于曲面拟合的光学偏折系统显示屏标定方法

针对透射式光学偏折系统中最关键的标定环节,提出使用曲面拟合方式拟合显示屏幕面形分布。建立基于透射式光学偏折术的波前检测仿真模型,分析两种不同的显示屏面形拟合方法对波前测量的影响。仿真结果显示：平面屏幕模型波前像差均方根误差(RMS)值为0.837 5μm,而曲面屏幕模型仿真波前像差RMS值仅为0.059 6μm。采用透射式光学偏折系统对球面透镜进行波前测量,曲面屏幕模型中波前像差RMS值为0.137 1μm,平面屏幕模型中波前像差RMS值为1.432 6μm。实验结果表明：使用曲面拟合效果明显优于平面拟合效果,证明了曲面拟合屏幕模型的可行性。     

Chemical imaging sensor and laser beacon

Design and functional aspects of PANSPEC, a panoramic-imaging chemical vapor sensor (PANSPEC is an abbreviation for infrared panoramic-viewing spectroradiometer), were advanced and its optical system reoptimized accordingly. The PANSPEC model unites camera and fused solid-state interferometer and photopolarimeter subsystems. The camera is an eye of the open atmosphere that collects, collimates, and images ambient infrared radiance from a panoramic field of view (FOV). The passive interferometer rapidly measures an infrared-absorbing (or infrared-emitting) chemical cloud traversing the FOV by means of molecular vibrational spectroscopy. The active photopolarimeter system provides a laser beam beacon. This beam carries identification (feature spectra measured by the interferometer) and heading (detector pixels disclosing these feature spectra) information on the hazardous cloud through a binary encryption of Mueller matrix elements. Interferometer and photopolarimeter share a common configuration of photoelastic modulation optics. PANSPEC was optimized for minimum aberrations and maximum resolution of image. The optimized design was evaluated for tolerances in the shaping and mounting of the optical system, stray light, and ghost images at the focal plane given a modulation transfer function metric.     

Earth-to-geosynchronous satellite laser beam transmission

Some experimental results for detection of a ground-based laser beacon by a geosynchronous satellite are reported. A 50-cm diam telescope and silicon intensifier tube camera were used for optical observation of the satellite. The transmitted argon laser beam was detected by the visible channel of a radiometer on board the Japanese Geostationary Meteorological Satellite. Two activities, (1) orbit prediction correction using optical observation and (2) detection of the earth laser beacon by the radiometer, are described.     

Branch-point reconstruction in laser beam projection through turbulence with finite-degree-of-freedom phase-only wave-front correction

Wave-front sensing and deformable mirror control algorithms in adaptive optics systems are designed on the premise that a continuous phase function exists in the telescope pupil that can be conjugated with a deformable mirror for the purpose of projecting a laser beam. However, recent studies of coherent wave propagation through turbulence have shown that under conditions where scintillation is not negligible, a truly continuous phase function does not in general exist as a result of the presence of branch points in the complex optical field. Because of branch points and the associated branch cuts, least-squares wave-front reconstruction paradigms can have large errors. We study the improvement that can be obtained by implementing wave-front reconstructors that can sense the presence of branch points and reconstruct a discontinuous phase function in the context of a laser beam projection system. This study was conducted by fitting a finite-degree-of-freedom deformable mirror to branch-point and least-squares reconstructions of the phase of the beacon field, propagating the corrected field to the beacon plane, and evaluating performance in the beacon plane. We find that the value of implementing branch-point reconstructors with a finite-degree-of-freedom deformable mirror is significant for optical paths that cause saturated log-amplitude fluctuations.     

空间交会对接标志灯发光器件的选择与分析

对主动标志灯与被动标志灯以及LD与LED的主要性能进行了比较,结果表明,主动标志和LED具有功耗低和稳定性强的优点。从LED的作用距离分析和发光强度分析两方面完成了LED用作标志灯发光器件可行性的理论分析。为了验证理论分析的正确性,进行了实验研究。使用中等分辨率摄像机做观测设备,在最低照度0.02lux时,辐射功率为6mW,辐射半顶角为25o的LED作用距离可以远至1.5km。理论分析和实验研究结果均表明,选用LED作为标志灯的发光器件可以降低系统功耗,提高系统的可靠性,对于实际空间交会对接有重要意义。     

白天用CCD摄象机对天体目标的探测及实验

文中介绍了用ＣＣＤ摄象机及相应的光学系统对天体目标的探测能力计算及白天用ＣＣＤ摄象机对天体目标的探测实验。给出了计算被测天体目标星等的计算表达式，指出白天在天空背景亮度在１２００ｃｄ／ｍ~２至２７００ｃｄ／ｍ~２时用普通低照度ＣＣＤ摄象机与大口径天文望远镜配合可探测到４至４．６等星     

"Molecular beacon"-based fluorescent assay for selective detection of glutathione and cysteine

We report on the development of a fluorescence turn-on "molecular beacon" probe for the detection of glutathione (GSH) and cysteine (Cys). The method is based on a competitive ligation of Hg(2+) ions by GSH/Cys and thymine-thymine (T-T) mismatches in a DNA strand of the self-hybridizing beacon strand. The assay relies on the distance-dependent optical properties of the fluorophore/quencher pair attached to the ends of the molecular beacon DNA strand. In a very selective coordination of Hg(2+) to GSH/Cys, the fluorophore/quencher distance increases concomitantly with the dehybridization and dissociation of the beacon stem T-Hg(2+)-T due to the extraction of Hg(2+) ions. This process results in switching the molecular beacon to the "on" state. The concentration range of the probe is 4-200 nM with the limit of detection (LOD) of 4.1 nM for GSH and 4.2 nM Cys. The probe tested satisfactorily against interference for a range of amino acids including sulfur-containing methionine.     

Calculation of holograms from elemental images captured by integral photography

We describe a method in which holograms can be produced by calculation from images captured by integral photography (IP). We present a basic algorithm obtained by simulating IP reconstruction, in which conditions are set so as not to cause aliasing in the holograms after the calculations. To reduce the calculation load, we also propose a way to limit the range of calculation considering the distribution of light and a way to shift the optical field on the exit plane of microlenses in a lens array. Finally, by optical experiments, we confirm that three-dimensional images can be reconstructed from holograms calculated from an integral photograph of a real object captured with an IP camera.     

Optical design of the wide angle camera for the Rosetta mission

The final optical design of the Wide Angle Camera for the Rosetta mission to the P/Wirtanen comet is described. This camera is an F/5.6 telescope with a rather large 12 degrees x 12 degrees field of view. To satisfy the scientific requirements for spatial resolution, contrast capability, and spectral coverage, a two-mirror, off-axis, and unobstructed optical design, believed to be novel, has been adopted. This configuration has been simulated with a ray-tracing code, showing that theoretically more than 80% of the collimated beam energy falls within a single pixel (20" x 20") over the whole camera field of view and that the possible contrast ratio is smaller than 1/1000. Moreover, this novel optical design is rather simple from a mechanical point of view and is compact and relatively easy to align. All these characteristics make this type of camera rather flexible and also suitable for other space missions with similar performance requirements.     

Development of an atmospheric Cherenkov imaging camera for the CANGAROO-III experiment

A Cherenkov imaging camera for the CANGAROO-III experiment has been developed for observations of gamma-ray-induced air showers at energies from 10¹¹ to 10¹⁴ eV. The camera consists of 427 pixels, arranged in a hexagonal shape at 0.17° intervals, each of which is a -in. diameter photomultiplier module with a Winston-cone-shaped light guide. The camera was designed to have a large dynamic range of signal linearity, a wider field of view, and an improvement in photon-collection efficiency compared with the CANGAROO-II camera. The camera, and a number of the calibration experiments made to test its performance, are described in detail in this paper.     

Beam width and transmitter power adaptive to tracking system performance for free-space optical communication

The basic free-space optical communication system includes at least two satellites. To communicate between them, the transmitter satellite must track the beacon of the receiver satellite and point the information optical beam in its direction. Optical tracking and pointing systems for free space suffer during tracking from high-amplitude vibration because of background radiation from interstellar objects such as the Sun, Moon, Earth, and stars in the tracking field of view or the mechanical impact from satellite internal and external sources. The vibrations of beam pointing increase the bit error rate and jam communication between the two satellites. One way to overcome this problem is to increase the satellite receiver beacon power. However, this solution requires increased power consumption and weight, both of which are disadvantageous in satellite development. Considering these facts, we derive a mathematical model of a communication system that adapts optimally the transmitter beam width and the transmitted power to the tracking system performance. Based on this model, we investigate the performance of a communication system with discrete element optical phased array transmitter telescope gain. An example for a practical communication system between a Low Earth Orbit Satellite and a Geostationary Earth Orbit Satellite is presented. From the results of this research it can be seen that a four-element adaptive transmitter telescope is sufficient to compensate for vibration amplitude doubling. The benefits of the proposed model are less required transmitter power and improved communication system performance.