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斑点干涉成像技术是克服大气湍流影响,提高地面大口径望远镜分辨本领的有效途径之一。该技术利用斑点相机拍摄一系列的短曝光像,使得大气湍流冻结,再经过图像处理获得高分辨率重建像。该技术设备简单,易于实现,很快在观测天文学中得到了广泛的应用,尤其是对双星的研究。首先回顾了天文高分辨率重建技术的发展,并介绍了相关研究成果。描述了几种典型的斑点干涉成像处理方法及其优缺点。对图像噪声类型及滤波方法进行了分析。在上海天文台1.56m望远镜上开展了双星斑点干涉观测实验,目标星等4~7mag,双星目标星等差小于2。分别采用斑点干涉术和迭代位移叠加法成功实现了双星目标的高分辨率成像,初步证明了在1.56m望远镜上进行斑点干涉成像实验,能够达到接近望远镜衍射极限的分辨率水平。 相似文献
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讨论了电子倍增电荷耦合器件(Electron-Multiplying Charge-Coupled Device,EMCCD)附加噪声的产生机理及特性,通过模拟详细分析了EMCCD附加噪声对天文图像高分辨统计重建技术——斑点干涉术传递函数信噪比的影响,并和实验进行了对比,结果表明,在星体暗弱时,由附加噪声引入的偏差将使斑点干涉术重建的信噪比下降,严重影响重建的结果,必须加以改正.由实测数据重建结果可以看出,噪声偏差改正模型基本解决了EMCCD附加噪声对斑点干涉术在重建目标自相关或模时的影响. 相似文献
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基于相位差方法的天文目标高分辨率成像,是利用在焦面和离焦位置上同时采集的一对或者多对短曝光图像,对目标和大气湍流引入的波前相位分布进行估计.在计算机模拟望远镜成像系统和相位差方法图像采集过程的基础上,利用信号估计和最优化理论,确定了高斯噪声模型下的目标函数,采用适合于大规模无约束优化的有限内存拟牛顿法对图像恢复问题进行了数值求解.恢复结果表明,基于相位差方法的高分辨成像技术,可以有效地克服大气湍流的影响,解决天文扩展目标的图像恢复问题. 相似文献
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《天文研究与技术》2015,(2)
抚仙湖1 m新真空太阳望远镜(New Vacuum Solar Telescope,NVST)利用多波段成像系统对太阳光球和色球同时进行高分辨成像观测,并对观测图像进行多波段同步高分辨统计重建,以大幅度降低重建所需的计算量,并改善低信噪比波段的高分辨重建效果。大气色散是影响多波段同步高分辨重建效果的主要因素。借助多层湍流大气的模拟,通过比较不同天顶角下色散引起的波像差、相对谱比,分析了大气色散对多波段同步高分辨重建的影响。分析结果表明对于1 m太阳望远镜,当天顶角在60°以内时,色散对近红外以及波长相差不大的可见光波段的多波段同步高分辨重建的影响较小,而393.3 nm波段受色散的影响明显,天顶角超过45°时分辨率明显下降。 相似文献
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大气湍流导致地基望远镜成像模糊,高分辨图像重建是解决这一问题的有效方法,K-T高分辨图像重建方法是其中常用的一种,但存在数据大、计算复杂等因素的制约,导致重建非常耗时。针对当前中央处理器与图形处理器混合架构下的高分辨图像重建开展研究,采用MPI-CUDA混合并行技术,最终实现了一套在单机图形处理器环境下基于斑点图像重建技术的高分辨太阳图像重建系统。通过实验验证,与单一的信息传递接口并行相比,图像子块的处理速度有了显著提升,在8个子进程下整个流程的加速比达到了2。实验结果表明,MPI-CUDA混合并行的有效性,能够为天文研究中的大规模计算任务提供借鉴和参考。 相似文献
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In recent years, post-facto image-processing algorithms have been developed to achieve diffraction-limited observations of the solar surface. We present a combination of frame selection, speckle-masking imaging, and parallel computing which provides real-time, diffraction-limited, 256×256 pixel images at a 1-minute cadence. Our approach to achieve diffraction limited observations is complementary to adaptive optics (AO). At the moment, AO is limited by the fact that it corrects wavefront abberations only for a field of view comparable to the isoplanatic patch. This limitation does not apply to speckle-masking imaging. However, speckle-masking imaging relies on short-exposure images which limits its spectroscopic applications. The parallel processing of the data is performed on a Beowulf-class computer which utilizes off-the-shelf, mass-market technologies to provide high computational performance for scientific calculations and applications at low cost. Beowulf computers have a great potential, not only for image reconstruction, but for any kind of complex data reduction. Immediate access to high-level data products and direct visualization of dynamic processes on the Sun are two of the advantages to be gained. 相似文献
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Jacques M. Beckers 《Experimental Astronomy》1991,2(1):57-71
Maximum sensitivity for optical interferometers is achieved only when the optical pathlengths between the different arms can be equalized without using interference fringes on the research object itself. This is called blind operation of the interferometer. In this paper I examine different options to achieve this, focussing on the application to the Very Large Telescope Interferometer (VLTI). It is proposed that blind operation should be done using a so-called coherence autoguider, working on an unresolved star of magnitude V=11 to 13 within the isoplanatic patch for coherencing, which has a diameter of about 1 degree. Estimates of limiting magnitudes for the VLTI are also derived. 相似文献
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Harold A. McAlister 《Icarus》1977,30(4):789-792
The applicability of the technique of speckle interferometry to the problem of detecting faint planetary and stellar objects around nearby stars is considered. Direct resolution could not be expected to reveal planetary objects, although many faint stellar objects should be detectable with a speckle camera of large dynamic range. The most promising possibilities lie with the approximately 100 nearby visual binaries with separations ?3 arcsec. Continued speckle interferometric observation of these systems could detect perturbations with amplitudes similar to those detectable by an ideal astrometric telescope. A simple scheme for measurement the fringe spacing in the composite spatial frequency power spectrum of the visual binary Eta Orionis indicates that relative separations with accuracies of 0″.002 in each coordinate are attainable. Use as reference stars of faint background stars lying within the isoplanatic patch of a nearby star is also considered. 相似文献
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大气湍流极大限制了地基大口径望远镜观测天文目标图像的空间分辨率.根据最大似然估计原理,提出了用实际光学带宽约束的可有效减小天文观测图像中大气湍流影响的盲反卷积方法,通过共轭梯度优化算法使卷积误差函数趋向最小.建立了望远镜光学系统参数和图像频域带宽的关系,采用变量正性约束、点扩散函数带宽有限约束,提高算法的收敛性.为避免图像处理中有效傅立叶变换频率超出截止频率,要求采集望远镜焦面图像时单个成像单元(如CCD像素单元)应小于四分之一衍射斑直径.算法中未用目标支持域约束,所提出的方法适用于全视场天文图像恢复.用计算机模拟和对实际天文目标双鱼座图像数据的恢复结果验证了所提出方法的有效性. 相似文献
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用于自适应光学系统的激光引导星 总被引:2,自引:0,他引:2
自适应光学系统应用于天文观测时应满足一些技术要求,其中的关键技术之一是自适应光学系统为了对畸变的光波进行采样,需要在其很小的等晕角内有足够的信标强度。激光引导星,即人造信标,就是解决这种问题的方法之一。特别是在观测天文暗目标时,其自身的光强度不能为有探测提供信息,激光引导星就蛤得非常重要。根据国际上的最新进展对激光引导星技术给予了介绍。重点介绍了激光引导星的局限性,对近几年提出的对激光引导星可能的 相似文献
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本文介绍在怀柔60cm多通道太阳望远镜上运用斑点干涉像复原方法所取得的一些初步结果,对用短暴光方法(暴光时间不大于10毫秒)获得的一系列“冻结”大气后的目标像用斑点干涉像复原方法进行处理,即可获得消除了地球大气影响的目标复原像,斑点掩模法即为斑点干涉像复原方法的一种,我们用它对日面中心的宁静区米粒进行处理,复原出了分率不劣于0.〃5的白光米粒象。 相似文献
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Britt R. Scharringhausen Philip D. Nicholson Thomas L. Hayward Mitchell Troy 《Icarus》2003,162(2):385-390
We report near-infrared observations of Prometheus and Janus taken on 9 and 13 November 2000 (UT) with the Palomar Adaptive Optics System on the 5-m Hale telescope at Palomar Observatory. Dione, Rhea, and Tethys were used as guide “stars” for the adaptive optics system, and, though they were outside the isoplanatic patch of the region of interest, they allowed significant correction of the atmospheric turbulence.Prometheus, which is usually impossible to observe from the ground due to scattered light from the A ring, was imaged at superior conjunction with Saturn. At the time of the observations, the rings of Saturn were blocked by the southern limb of the planet while the moon passed just 0.35″ below the planet’s south pole. A K filter, in a methane absorption band, was used to suppress light from the disk of the planet, and template subtraction removed much of the scattered light from the A ring. Prometheus was found to be 21.9 ± 0.1° of mean longitude behind the position predicted by Voyager-era ephemerides, consistent with the orbital lag discovered during the 1995 ring-plane crossing. 相似文献
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In this paper we propose to use the method of iterative calculation to solve directly the imaging equation for image recovery. The same method can be applied to the recovery of one-dimensional spectra. During the iteration suitable constraints are applied to effect nonlinear control over the process. The use of fitting technique in the treatment of the imaging equation suppresses noise and raises sensitivity. Analyses of both Monte Carlo samples and actual high-energy astronomical data showed that the direct method is more sensitive and having greater resolving power than the traditional method, is capable of revealing simultaneously both diffuse and discrete structures in the target object and can be used on data of lower statistical quality. In principle, the direct method can be used in all types of image and spectrum recovery in other fields. 相似文献
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为了获取LAMOST焦面板上光纤的零位位置,提出了一种基于分离式标准靶标的高精度摄影测量方法。首先,根据Tsai摄像机标定参数模型介绍了CCD相机的标定原理。然后介绍了用光重心算法求取靶标发光点像面坐标及通过球面三角公式计算靶标发光点物面坐标。接着,利用最小二乘法导出了含标定参数的方程组。最后,介绍了标准靶标的放置方法以及提高光纤位置测量精度的靶标取法。实验结果表明:CCD相机的标定残差平均值为8.8μm;标定残差的标准差为5.3μm。测量方法简单易行,通过仔细分析,找出了残差偏大的原因,对后续进一步测量实验有重要指导意义。 相似文献
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Adaptive Optics on Large Telescopes 总被引:2,自引:0,他引:2
Observations withground based telescopes suffer from atmospheric turbulence.Independent of the telescope size the angular resolution inthe visible is equivalent to that of a telescope with adiameter of 10–20 cm. This effect is caused by the turbulentmixing of air with different temperatures in the atmosphere.Thus, the perfect plane wave from a star at infinity isaberrated before it enters the telescope. In the following,we will discuss the physical background of imaging throughturbulence, using Kolmogorov statistics, and the differenttechniques to sense and to correct the wave-front aberrationswith adaptive optics. The requirements for the control loop ofan adaptive optics system are discussed including formulas forthe limiting magnitude of the guide star as a function of thewave-front sensing method, of the quality of the wave-frontsensor camera, and of the degree of correction. Finally, ashort introduction to deformable mirror technology will begiven followed by the presentation of a new method to measureand to distinguish individual turbulent layers in order toincrease the isoplanatic angle. 相似文献