统计传递函数估计误差对NVST高分辨算法重建结果的影响分析

发布时间：2018-12-10 19:21

【摘要】：抚仙湖1 m新真空太阳望远镜(New Vacuum Solar Telescope,NVST)作为目前国内口径最大的地基太阳望远镜,有着给太阳物理研究人员提供高质量高分辨率的观测数据的使命。统计传递函数的正确估计是NVST图像重建的关键一步,但是望远镜像差、光子噪声、非等晕效应等因素都可能使传递函数的估计产生偏差。在高分辨太阳数据的实际数据处理中,统计传递函数的估计误差会导致高分辨数据处理结果分辨率降低,甚至失真。所以必须要研究统计传递函数的估计误差对高分辨图像重建结果的影响,从而获得更好分辨率的重建图像。本文基于斑点重构算法理论,采用理论推导、数值模拟、实测数据重建三者结合的方式研究了像差、噪声、非等晕效应对NVST高分辨算法重建结果的影响,主要考虑两个方面:1.误差对算法重建目标傅里叶模的影响;2.误差对算法重建目标相位的影响。本文完成的主要工作如下:1)分析了相同大气视宁度情况下,同类型像差不同像差大小对NVST高分辨重建结果的影响;相同大气视宁度情况下,不同类型像差相同像差大小对NVST高分辨重建结果的影响;视宁度不同时,同类型像差相同像差大小对NVST高分辨重建结果的影响。2)分析了光子噪声对图像功率谱重建的影响;不同大气视宁度常数情况下,不同光子噪声对谱比曲线的影响;不同大气视宁度常数,不同光子噪声对NVST算法重建结果的影响以。3)推导了非等晕效应对斑点干涉术、斑点掩模法、谱比法估计传递函数的影响。采用数值模拟的方法模拟出了非等晕效应,以不同子块大小对实测光球数据进行重建,使用图像平均功率谱分析了非等晕效应对NVST高分辨图像重建结果的影响。当像差大小不超过一定范围时,像差并不会对重建结果产生太大影响。当像差大小超过一定范围时,像差会影响重建结果且随着像差的增加和大气视宁度的变好这种影响会更加明显。离焦像差和球差对图像重建影响比较大。光子噪声在斑点图功率谱引入了偏差,在重建的时候会出现一种高频放大现象,导致研究人员想要重建的高频信息无法有效复原。在大气视宁度相对比较好的时候,光子噪声对谱比曲线的影响比较大,这会使对斑点干涉术传递函数的估计有偏差。在视宁度相对比较差的时候,光子噪声会使重谱法递推相位的重建精度明显降低。非等晕误差对大视场目标重建存在影响,会使斑点干涉术重建结果不准确而导致图像分辨率下降。为了重建图像有更好的分辨率,最好以等晕区大小分块,这样非等晕效应的影响最小,甚至可以忽略。
[Abstract]:As the largest ground-based solar telescope in China, Fuxian Lake 1 m vacuum Solar Telescope (New Vacuum Solar Telescope,NVST) has the mission of providing high quality and high resolution observation data to Heliophysical researchers. The correct estimation of the statistical transfer function is a key step in the reconstruction of NVST images, but the aberration of the telescope, the photon noise and the non-isobaric effect may lead to the deviation of the estimation of the transfer function. In the actual data processing of high-resolution solar data, the estimation error of the statistical transfer function will result in the resolution of the high-resolution data processing reduced or even distorted. Therefore, it is necessary to study the effect of the estimation error of statistical transfer function on the reconstruction results of high-resolution images, so as to obtain a better resolution of reconstructed images. Based on the theory of speckle reconstruction algorithm, the effects of aberration, noise and non-equal-halo effect on the reconstruction results of NVST high resolution algorithm are studied by theoretical derivation, numerical simulation and real data reconstruction. Two main considerations: 1. The effect of error on the Fourier mode of target reconstruction. 2. The effect of error on the phase reconstruction of target. The main work of this paper is as follows: 1) the effects of different aberrations of the same type of aberrations on the reconstruction results of NVST with the same atmospheric apparent degree are analyzed. The effect of the same aberration size of different types of aberrations on the high resolution reconstruction results of NVST under the same atmospheric apparent intensity; The effect of the same type aberration and the same aberration on the reconstruction results of NVST high resolution is analyzed. 2) the influence of photon noise on image power spectrum reconstruction is analyzed. The influence of different photon noise on the spectral ratio curve under different atmospheric apparent degree constants; Effects of different Atmospheric apparent Nine constants and different Photon noise on the Reconstruction results of NVST algorithm. 3) the effects of non-equal-halo effect on speckle interferometry speckle mask method and spectral ratio method for estimating transfer function are derived. The non-equal-halo effect is simulated by numerical simulation, and the measured optical sphere data are reconstructed with different sub-block sizes. The effect of non-equal-halo effect on the reconstruction results of NVST high-resolution image is analyzed by using the average power spectrum of the image. When the aberration is not larger than a certain range, the aberration does not have much influence on the reconstruction results. When the aberration is larger than a certain range, the aberration will affect the reconstruction result and become more obvious with the increase of aberration and the improvement of atmospheric apparent degree. Defocus aberration and spherical aberration have great influence on image reconstruction. Photon noise induces bias in speckle power spectrum, and a high frequency amplification phenomenon occurs during reconstruction, which leads to the failure to recover the high frequency information that researchers want to reconstruct. When the atmospheric apparent degree is relatively good, the photon noise has a great influence on the spectral ratio curve, which will make the estimation of the speckle interferometry transfer function biased. When the apparent noise is relatively poor, the reconstruction accuracy of the recursive phase of the respectral method is obviously reduced by the photon noise. The effect of non-equal-halo error on the reconstruction of large field of view object will make the reconstruction result of speckle interferometry inaccurate and result in the decrease of image resolution. In order to improve the resolution of the reconstructed image, it is better to divide the image into blocks with the size of the equal-halo region, so that the effect of the non-isobaric effect can be minimized or even ignored.
【学位授予单位】：中国科学院大学(中国科学院云南天文台)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P111.41

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