QQ客服 官方微博 反馈留言

题名	EMCCD在天文高分辨成像中的应用
作者	张向波
学位类别	硕士
答辩日期	2012-05
授予单位	中国科学院研究生院（云南天文台）
授予地点	北京
导师	金振宇
关键词	高分辨统计重建方法 Lucky Imaging 附加噪声 选帧技术
其他题名	Application of Electron Multiplying CCDs in Astronomical High-Resolution Imaging
学位专业	天文技术与方法
中文摘要	对星体的高分辨率成像是天文观测的重要目标之一，尤其是对暗弱星体的高分辨成像。但是受大气湍流的影响，星体入射光波前发生畸变，地基望远镜无法实现衍射极限成像。目前消除大气湍流实现天文高分辨成像的主要方法有自适应光学、高分辨统计重建技术和Lucky Imaging。自适应光学由于仪器造价昂贵，实现起来相对困难，而高分辨统计重建方法和Lucky Imaging实现起来相对容易。 高分辨统计重建方法和Lucky Imaging都是对目标的多幅短曝光斑点图进行某种方式的统计，从而保留目标高频信息重建出接近望远镜衍射极限的高分辨像。采集到大量目标高质量短曝光图像是高分辨统计重建方法和Lucky Imaging的首要工作，所以选用合适的探测器是关键。目前，满足天文观测的探测器有常规CCD、增强型CCD（ICCD）、EMCCD等类型，而常规CCD中读出噪声小的其读出速度慢，难以获得短曝光图像；读出速度快的其读出噪声大，斑点图信噪比不高。ICCD虽然有电子倍增效应，但是其量子效率低。EMCCD相对于常规CCD和ICCD具有读出速度快、读出噪声小、高量子效率、微光探测能力、有利于获得短曝光图像等特点，目前成功应用于暗弱目标的高分辨成像中。虽然EMCCD相对于常规CCD和ICCD可获得信噪比高的短曝光图像，但是其附加噪声不同于常规CCD和ICCD，其附加噪声对天文目标高分辨成像产生的影响是本文研究的重点。 本文首先在前沿和第一章中简要介绍了高分辨统计重建技术和Lucky Imaging，讨论了各种高分辨统计重建方法的传递函数。在第二章详细分析了EMCCD附加噪声的产生机理及特性，并且对附加噪声进行了实测。其次，第三章在理论分析基础上通过数值模拟深入研究了EMCCD各种附加噪声对高分辨统计重建方法在天文暗弱目标成像时的影响，利用提出的噪声偏差改正模型对噪声偏差进行了改正。在第四章中提出了基于选帧技术的高分辨统计重建方法，通过数值模拟研究了基于选帧技术的高分辨统计重建方法在探测暗弱星体时的影响因素，提出了移位叠加时图像对齐的方法，以及如何提高暗弱目标高分辨统计重建精度的方法。对模拟数据和实测数据处理的结果表明，基于选帧技术的高分辨统计重建方法可以提高暗弱目标探测精度。最后第五章对本文的研究工作进行了总结，对未来工作进行了展望。
英文摘要	The high-resolution imaging of stars is one of the important goals of astronomical observations, especially the high-resolution imaging of faint stars. However, due to the influence of atmospheric turbulence, stellar incident light wave front is degraded so that ground-based telescopes can’t achieve the diffraction -limit imaging. At present, the methods of eliminating the effect of atmospheric turbulence and achieve high resolution imaging are Adaptive Optics, High Resolution Statistical Reconstruction Methods and Lucky Imaging. But because of the high expensive instrument, Adaptive Optics is relatively difficult to implement, while the High-Resolution Statistical Reconstruction Methods and Lucky Imaging are relatively easy to implement. Both of High Resolution Statistical Reconstruction Methods and Lucky Imaging make statistics to the short-exposure images in some way so as to preserve the high –frequency information of object to reconstruct the high resolution image close to telescope diffraction limit. Achieving plenty of high quality short exposure images of object is the primary job, so the appropriate detector is the key. At present, the main detectors meeting the satisfaction of astronomical observations are conventional CCDs, Intensified CCDs(ICCD) and Electron Multiplying CCDs(EMCCD). But Conventional CCDs with tiny readout noise have slow readout speed, difficult to achieve short exposure images. Other types of conventional CCDs have faster readout speed, but their readout noise is too much, difficult to achieve higher SNR. Although ICCD have electron multiplier effect, the quantum is too low. Compared with conventional CCDs and ICCDs, EMCCD have features of high quantum, tiny readout noise, high readout speed, low light level detection capability, much more easier to achieve high quality short-exposure images, so they are successfully applied to high resolution imaging of faint objects. Although EMCCD can achieve short exposure images of higher SNR, additive noises of EMCCD are different from conventional CCDs and ICCDs. The effect of additive noises on high resolution imaging is the focus of this study. Firstly, this paper briefly introduced the High Resolution Statistics Reconstruction Methods and Lucky Imaging, and discussed the transfer functions of the High Resolution Statistics Methods in chapter I. In Chapter II, after detailed analysis of the generation mechanism and characteristics of the EMCCD additive noises, measure of additive noises were made through experiments. Secondly, Chapter III in-depth study the effects of additive noises of EMCCD on the High Resolution Statistics Methods in faint subject imaging by numerical simulation on the basis of theoretical analysis. Meanwhile, noise deviation was corrected. In Chapter Ⅳ, we proposed High Resolution Statistical Reconstruction Methods on the base of Selected Frame Technology，and study the factors affecting High Resolution Statistical Reconstruction in the faint object imaging, proposed the new method of shift-and-add and the method of improving the High-Resolution Statistical Reconstruction accuracy. The results of simulation and real data processing show our proposed method could improve detection accuracy of faint object imaging. Finally, chapter Ⅴ are work summary and future plan.
语种	中文
学科主题	天文学
内容类型	学位论文
源URL	[http://ir.ynao.ac.cn/handle/114a53/4905]
专题	云南天文台_抚仙湖太阳观测站
推荐引用方式 GB/T 7714	张向波. EMCCD在天文高分辨成像中的应用[D]. 北京. 中国科学院研究生院（云南天文台）. 2012.

个性服务

查看访问统计

相关权益政策

暂无数据

收藏/分享

除非特别说明，本系统中所有内容都受版权保护，并保留所有权利。