共查询到18条相似文献，搜索用时 560 毫秒
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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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在简要介绍了由Hofmann等提出的迭代最小二乘法天文像复原法砌砖法(Building
block)的原理后，提出用斑点干涉术等方法对被观测目标像的范围大小进行大概估计的预处理方案，这样将做到对砖块的区域限定投放，避免大量无效的砖块投放迭代步骤。天文高分辨率像复原实验表明，砌砖法的效率被大大地提高了。 相似文献
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在简要介绍了由Hofmann等提出的迭代最小二乘法天文像复原法：砌砖法（Building block)的原理后，提出用斑点干涉术等方法对被观测目标像的范围大小进行大概估计的预处理方案，这样将做到对砖块的区域限定投放，避免大量无效的砖块投放迭代步骤，天文高分辨率像复原实验表明，砌砖法的效率被大大地提高了。 相似文献
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多层湍流大气相位屏的数值模拟 总被引：1，自引：0，他引：1
高分辨图像重建技术可以有效消除湍流大气的影响,重建目标的接近望远镜衍射极限的图像。但是当目标的视场角比较大时,大气—望远镜综合系统不再是线性空不变的,给图像重建带来新的困难,它是大气性质中的一个重要特性,对大气相位屏的模拟应该满足这一特性。提出了一种可以模拟等晕区效应的多层大气相位屏的数值模拟方法,这种方法可以应用于等晕区对高分辨统计重建方法的影响的研究中。利用该数值模拟方法模拟了5″和8″的双星的斑点图,用斑点干涉术对模拟的双星进行了重建,并与实测的双星的斑点干涉术重建结果进行了比较。比较结果表明该数值模拟方法所产生的等晕区效应与实际的等晕区效应相似。 相似文献
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给出了天文像复原“迭代位移叠加法”的第一步中确定位移基准点的方法-将目标像结构的初始信息与目标斑点图间的互相关性运算的极大值点作为基准点，按此基准点对目标斑点图进行位移叠加，第一步中初始信息的选择是展开迭代位移叠加过程的关键。讨论了目标初始信息的性质和提取方法。 相似文献
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We present an implementation of the extended Knox-Thompson (EKT) speckle reconstruction algorithm dedicated to solar observations.
EKT speckle imaging yields nearly diffraction-limited images from bursts of short exposure solar observations under a wide
range of seeing conditions. Our implementation supports field dependent amplitude calibration to permit analyzing data obtained
with a partially compensating adaptive optics systems. The principles of the method and some technical details of our implementation
are discussed. We have performed various tests using simulated data of representative solar scenes. The simulations include
the effects of seeing and noise with the exception of anisoplanatism. The expected photometric error of a reconstructed image
amounts to a few percent of the mean intensity under seeing conditions ranging from poor to excellent. We also present sample
reconstructions of real data and discuss issues arising from anisoplanatism. 相似文献
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首先介绍了斑点图形成机制以及获取方法,并借助计算机模拟了斑点图的生成。然后重点描述斑点图的图像重建方法,包括频率域和空间域重建方法。在频率域重建方法部分依次详细叙述了用于复原模信息的斑点干涉法和用于复原相位信息的由模复原相位法、Knox-Thompson法、斑点掩模法;空间域重建方法部分介绍了典型的LWH法和迭代位移叠加法;另外,盲消卷积法也为斑点图重建提供了新的思路,文章对此方法也做了介绍;特别地,还对国内在该领域的相关工作做了介绍;关于斑点图重建方法在天文学、天体物理学等领域的应用,文章做了有针对性的介绍;最后一章是斑点图图像重建方法的总结。 相似文献
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Irbah A. Bouzaria M. Lakhal L. Moussaoui R. Borgnino J. Laclare F. Delmas C. 《Solar physics》1999,185(2):255-273
Good edge extraction from temporal series of solar images is fundamental in the solar astrolabe experiment. Noise and spots in images cause however, difficulties to extract an accurate solar edge. We present in this paper a new image-processing method which solves this problem and thus improves the characteristics of the solar astrolabe experiment. The method is based upon the use of wavelet transform in the solar image analysis. It is developed to remove image defects (parasite spots) and noise without reducing image resolution. Solar images obtained at Calern Observatory astrolabe (France) are then processed using this method. Solar edges of these images are extracted and trajectories reconstructed. 相似文献
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Observations of the solar photosphere from the ground encounter significant problems caused by Earth’s turbulent atmosphere. Before image reconstruction techniques can be applied, the frames obtained in the most favorable atmospheric conditions (the so-called lucky frames) have to be carefully selected. However, estimating the quality of images containing complex photospheric structures is not a trivial task, and the standard routines applied in nighttime lucky imaging observations are not applicable. In this paper we evaluate 36 methods dedicated to the assessment of image quality, which were presented in the literature over the past 40 years. We compare their effectiveness on simulated solar observations of both active regions and granulation patches, using reference data obtained by the Solar Optical Telescope on the Hinode satellite. To create images that are affected by a known degree of atmospheric degradation, we employed the random wave vector method, which faithfully models all the seeing characteristics. The results provide useful information about the method performances, depending on the average seeing conditions expressed by the ratio of the telescope’s aperture to the Fried parameter, \(D/r_{0}\). The comparison identifies three methods for consideration by observers: Helmli and Scherer’s mean, the median filter gradient similarity, and the discrete cosine transform energy ratio. While the first method requires less computational effort and can be used effectively in virtually any atmospheric conditions, the second method shows its superiority at good seeing (\(D/r_{0}<4\)). The third method should mainly be considered for the post-processing of strongly blurred images. 相似文献
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G. Artzner 《Solar physics》1990,128(1):281-286
Observed temporal variations of shape and size of the solar disk as viewed from Earth may act as constraints for theories of the interior of the Sun. In addition to existing programs of solar diameter measurements we investigate a ground-based photographic method.The solar limb profile is recorded on a photoresist-coated substrate over a 20 radial length simultaneously all along the circonference as a three-dimensional 21 mm diameter, 0.0015mm thick permanent object available for inspection by interferometric methods. The exposure time is long enough for filtering much of the atmospheric turbulence, whereas the slope of the observed solar limb should help to locate a standard solar limb. The first results of February 1989 at large zenith distance and low altitude are a set of differential measurements of the position of a solar limb around a circle with, after taking into account the 3.7 atmospheric differential refraction, a 0.34r.m.s. dispersion of the residuals for a fit to a circular solar disk.We estimate that this method of accuracy comparable to other ground-based methods, with potentially more than 600 independent simultaneous measurements along the circonference, could help to discriminate between terrestrial and solar causes for variations of shape and size of the solar disk.We note that operation outside the Earth's atmosphere would provide access not only to undisturbed images but also to UV wavelengths, i.e., to a better definition of the solar limb. 相似文献
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We have applied the technique of speckle masking to spectra. The observation of elongated solar structures avoids the problem of missing information in one-dimensional spectra. Image motion perpendicular to the slit was diminished by a one-dimensional image stabilization system. The remaining influence of the Earth's atmosphere was removed by a modified speckle-masking algorithm, adapted to the single spatial dimension occurring in the spectra. The reconstructed spectra achieve the diffraction limit of the telescope and the spectrograph.The first application of this technique to observations of spicules and penumbral filaments reveals more details and also yield line profiles which differ from those before reconstruction. The H emission in spicules shows line-of-sight velocities two times larger than in the unprocessed spectra. The non-magnetic line Fe 709.03 nm shows penumbral line widths, reflecting mostly the line asymmetry from the Evershed effect, which are tightly correlated to the continuum intensity fluctuations. Our reconstruction increases the coherence between both from 0.6 to 0.8. 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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A. Zhitnik K. A. Boyarchuk O. I. Bugaenko G. S. Ivanov-Kholodnyi A. P. Ignat'ev V. V. Krutov S. V. Kuzin A. V. Mitrofanov S. N. Oparin A. A. Pertsov V. A. Slemzin A. I. Stepanov 《Solar System Research》2003,37(4):296-301
We consider the effects of the absorption of solar XUV radiation by the Earth's atmosphere that were observed in the solar images obtained with the TEREK-K telescope onboard the Coronas-I satellite in May–June 1994 at low solar activity and with the SPIRIT instrumentation onboard the Coronas-F satellite in October–November 2001 at maximum solar activity. The solar images were recorded during the satellite occultation: in the 175- and 304-A spectral ranges onboard Coronas-I with the TEREK-K telescope and in the 175-, 304-, and 8.42-A ranges onboard Coronas-F with the SPIRIT instrumentation. Based on the XUV solar images obtained during atmospheric sounding, apart from the total absorption, we can determine the direction of the atmospheric density gradient and study the local absorption variations with altitude on spatial scales of less than 1 km. The described method can significantly supplement the data obtained in studies of the upper atmosphere by the methods of mass spectrometry, incoherent radar scattering, and the drag of orbital spacecraft. 相似文献