基于波前探测的太阳偏振图像高分辨重建误差分析

YNAO OpenIR > 天文技术实验室

	基于波前探测的太阳偏振图像高分辨重建误差分析
其他题名	High-resolution Reconstruction Error Analysis of Solar Polarization Image Based on Wavefront Sensing
	吕卓
学位类型	硕士
导师	金振宇 ; 朱庆生
	2023-07-01
学位授予单位	中国科学院大学
学位授予地点	北京
学位专业	电子信息
关键词	太阳磁场测量高分辨率太阳偏振图像重建波前探测误差分析
摘要	地基太阳望远镜磁像仪在进行偏振测量时会受到大气湍流的影响，导致测量结果不准确。为克服大气湍流的影响，改善成像质量，可通过高分辨图像重建技术对退化图像进行重建，获得可用于进一步科学研究的高分辨率图像，该技术目前在各大高分辨太阳望远镜的成像观测仪器中均有应用。而对于偏振图像的高分辨重建，由于窄带滤光器的低光谱带宽和低透过率，导致偏振测量通道的光子数较少，短曝光图像信噪比较低，难以满足高分辨图像重建的要求；且由于探测器只对光强信息敏感，在偏振测量时，需首先将偏振光调制到背景光强中，再从采集到的图像中解调出偏振信息，该过程也要求用于解调的各调制态图像具有相同的重建质量，否则将在重建出的偏振信号中引入伪结构。为解决上述难题，地基高分辨磁像仪通常选用同步重建的方式对太阳偏振图像进行高分辨重建，即在太阳窄带偏振测量通道旁增加一条宽带通道以获得大气-望远镜系统的波前像差信息，再将其用于偏振图像的重建。本文对以波前探测器为宽带通道的同步重建方案进行了模拟研究，主要开展了以下两方面的工作： 1、对由于波前估计不准确而引入的偏振图像重建误差进行了仿真分析。由波前探测通道估计出波前像差后，可实现对窄带偏振图像的退卷积重建。当波前像差估计结果与真实波前不同时，会在解调得到的偏振图像中引入背景光强信号的串扰，该串扰来源于光强信号的中高频信息，且是零均值的，串扰的数值分布范围会随波前复原精度的提高而减小。并对增加用于图像重建的短曝光图像的帧数、低通滤波、不同信噪比等情况下串扰的影响进行了仿真。 2、基于 Adam 优化器，对相位差波前探测技术的求解精度进行了误差分析。相位差法是一种理想的太阳波前探测方案，本文经过仿真验证，发现相位差图像存在局部极值解，且在迭代优化求解的过程中，可能出现陷入该局部极值的情况。以相同的观测目标作为约束，使用多帧相位差图像对波前像差进行联合求解可提升各组相位差图像的求解精度，避开局部极值解。本文的研究工作和相应成果可为地基高分辨磁像仪设计光路结构、选择波前观测方案、制定偏振观测模式和处理观测数据提供参考。
其他摘要	The magnetic imager of ground-based solar telescope will be affected by atmospheric turbulence when conducting polarimetry, resulting in inaccurate measurement results. To overcome the impact of atmospheric turbulence and improve imaging quality, high resolution image reconstruction technology can be used to reconstruct degraded images and obtain high-resolution images that can be used for further scientific research. This technology is currently applied in imaging observation instruments of various high resolution solar telescopes. For the high resolution reconstruction of polarization im ages, due to the low spectral bandwidth and low transmittance of filters, the number of photons in the polarimetry channel is small, and the snr of short exposure images is low, which is difficult to meet the requirements of high-resolution image reconstruction. And because the detector is only sensitive to the light intensity information, in polarimetry, it is necessary to first modulate the polarized light into the background light intensity, and then demodulate the polarization information from the collected images. This process also requires that the modulated images used for demodulation have the same reconstruction quality, otherwise the error structure will be introduced into the reconstructed polarization signal. In order to solve the above problems, the ground based high-resolution magnetic imager usually uses synchronous reconstruction to reconstruct the solar polarization image, that is, add a broadband channel next to the solar narrowband polarimetry channel to obtain the wavefront aberration information of the atmosphere telescope system, and then use it to reconstruct the polarization image.The thesis conducts simulation research on a synchronous reconstruction scheme using wavefront detectors as broadband channels, mainly focusing on the following two aspects of work:1.Simulation analysis was conducted on the polarization image reconstruction error introduced due to inaccurate wavefront estimation. After estimating the wavefront aberration from the wavefront detection channel, deconvolution reconstruction of narrowband polarized images can be achieved. When the estimated wavefront aberration results are different from the real wavefront, crosstalk from the background light intensity signal will be introduced into the demodulated polarization image. The crosstalk originates from the medium to high frequency information of the light intensity signal and is zero mean. The numerical distribution range of crosstalk will decrease with the improvement of wavefront restoration accuracy. And the impact of crosstalk on increasing the number of frames, low-pass filtering, and different signal-to-noise ratios of short exposure images used for image reconstruction was simulated.2. Based on the Adam optimizer, error analysis was conducted on the solution accuracy of phase diversity wavefront detection technology. Phase diversity technology is an ideal solar wavefront sensing scheme. After simulation verification, it was found that there is a local extremum solution in the phase diversity image, and during the iterative optimization process, it may be trapped in this local extremum. Using the same observation target as a constraint and using multiple frames of phase diversity images to jointly estimate wavefront aberrations can improve the accuracy of solving each group of phase diversity images and avoid local extremum solutions.The research work in this paper and the corresponding results can provide reference for designing optical path structures, selecting wavefront sensing schemes, formulating polarization observation modes, and processing observation data for ground-based high resolution magnetic imager.
学科领域	天文学
学科门类	理学 ; 理学::天文学
页数	0
语种	中文
文献类型	学位论文
条目标识符	http://ir.ynao.ac.cn/handle/114a53/26419
专题	天文技术实验室
作者单位	中国科学院云南天文台
第一作者单位	中国科学院云南天文台
推荐引用方式 GB/T 7714	吕卓. 基于波前探测的太阳偏振图像高分辨重建误差分析[D]. 北京. 中国科学院大学,2023.

条目包含的文件
文件名称/大小	文献类型	版本类型	开放类型	使用许可
基于波前探测的太阳偏振图像高分辨重建误差（11403KB）	学位论文		开放获取	CC BY-NC-SA	浏览请求全文