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arXiv 1802.00760astro-ph.SR
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高分辨率、高拍频太阳成像中的图像质量

Image Quality in High-resolution and High-cadence Solar Imaging

C. Denker, E. Dineva, H. Balthasar, M. Verma, C. Kuckein, A. Diercke, S. J. González Manrique

摘要:

宽带成像,甚至具有中等带通(约1 nm)的成像提供了一个“光子丰富”的环境,其中帧选择(“幸运成像”)成为一个有用的工具,在图像恢复,使我们能够进行成本效益分析,如何设计观察序列的高空间分辨率成像结合实时校正所提供的自适应光学(AO)系统。本研究提出了高节奏(160 Hz)的G波段和蓝色连续图像序列获得的高分辨率快速成像仪(HiFI)在1.5米的GREGOR太阳望远镜,斑点掩蔽技术被用来恢复图像与近衍射极限的分辨率。HiFI采用两个同步的大幅面和高节奏sCMOS探测器。中值滤波梯度相似性(MFGS)图像质量指标应用于2017年6月4日和5日观测到的孔隙和小太阳黑子的AO校正图像序列。为快速成像性能而选择的一个小的感兴趣区域覆盖了这些对比度丰富的特征及其邻域,这些特征及其邻域是活动区域NOAA 12661的一部分。MFGS算法的修改揭示了该图像质量度量的场和结构依赖性。然而,MFGS仍然是一个很好的选择,确定图像质量没有先验知识,这是一个重要的特点时,分类的大量高分辨率图像中包含的数据档案。此外,这项调查表明,一个快速的节奏和毫秒曝光时间仍然不足以达到白天看到的相干时间。尽管如此,分析表明,需要超过50 Hz的数据采集速率才能捕获相当大一部分最佳视觉时刻,从而显着提高事后图像恢复的性能。

英文摘要:

Broad-band imaging and even imaging with a moderate bandpass (about 1 nm) provides a "photon-rich" environment, where frame selection ("lucky imaging") becomes a helpful tool in image restoration allowing us to perform a cost-benefit analysis on how to design observing sequences for high-spatial resolution imaging in combination with real-time correction provided by an adaptive optics (AO) system. This study presents high-cadence (160 Hz) G-band and blue continuum image sequences obtained with the High-resolution Fast Imager (HiFI) at the 1.5-meter GREGOR solar telescope, where the speckle masking technique is used to restore images with nearly diffraction-limited resolution. HiFI employs two synchronized large-format and high-cadence sCMOS detectors. The Median Filter Gradient Similarity (MFGS) image quality metric is applied, among others, to AO-corrected image sequences of a pore and a small sunspot observed on 2017 June 4 and 5. A small region-of-interest, which was selected for fast imaging performance, covered these contrast-rich features and their neighborhood, which were part of active region NOAA 12661. Modifications of the MFGS algorithm uncover the field- and structure-dependency of this image quality metric. However, MFGS still remains a good choice for determining image quality without a priori knowledge, which is an important characteristic when classifying the huge number of high-resolution images contained in data archives. In addition, this investigation demonstrates that a fast cadence and millisecond exposure times are still insufficient to reach the coherence time of daytime seeing. Nonetheless, the analysis shows that data acquisition rates exceeding 50 Hz are required to capture a substantial fraction of the best seeing moments, significantly boosting the performance of post-facto image restoration.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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