DETECTION AND RESTORATION OF NON-RADIAL VARIATION OVER FULL-DISK SOLAR IMAGES
DETECTION AND RESTORATION OF NON-RADIAL VARIATION OVER FULL-DISK SOLAR IMAGES
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DOI：
10.5303/jkas.2013.46.5.191
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发表时间：
2013-10
影响因子：
1
通讯作者：
Yunfei Yang;Jiaben Lin;Song Feng;H. Deng;Feng Wang;Kaifan Ji
中科院分区：
文献类型：
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作者：
Yunfei Yang;Jiaben Lin;Song Feng;H. Deng;Feng Wang;Kaifan Ji
全圆盘太阳图像由世界各地的许多太阳望远镜提供。然而，所观察到的图像显示在盘上的非径向变化（NRV）。在本文中，我们提出了检测失真和恢复这些图像的算法。为了检测NRV，计算径向剖面的互相关系数矩阵，并将矩阵中的最小值定义为非径向变化指数（INV）。利用该指标对GONG的Hα图像进行了评价，得到了不同仪器的系统变化。为了获得NRV的图像，设计了一种多级形态滤波器（MMF）来消除太阳活动在太阳表面产生的结构。与中值滤波相比，该滤波器是一种更好的选择。实验结果表明，本文提出的自动检测和复原方法效果显著，能够得到平坦、高对比度的全光盘图像。为了研究我们的方法对太阳特征的影响，使用了结构相似性（SSIM）指数。高SSIM指数（接近1）的太阳特征表明，结构的细节保留后，NRV恢复。
Full-disk solar images are provided by many solar telescopes around the world. However, the observed images show Non-Radial Variation (NRV) over the disk. In this paper, we propose algorithms for detecting distortions and restoring these images. For detecting NRV, the cross-correlation coefficients matrix of radial profiles is calculated and the minimum value in the matrix is defined as the Index of Non-radial Variation (INV). This index has been utilized to evaluate the Hα images of GONG, and systemic variations of different instruments are obtained. For obtaining the NRV’"s image, a Multi-level Morphological Filter (MMF) is designed to eliminate structures produced by solar activities over the solar surface. Comparing with the median filter, the proposed filter is a better choice. The experimental results show that the effect of our automatic detection and restoration methods is significant for getting a flat and high contrast full-disk image. For investigating the effect of our method on solar features, structural similarity (SSIM) index is utilized. The high SSIM indices (close to 1) of solar features show that the details of the structures remain after NRV restoring.