人造钠信标波前探测算法研究

发布时间：2018-02-22 23:23

本文关键词： 自适应光学人造钠信标波前探测光斑形态质心提取算法　出处：《中国科学院研究生院(光电技术研究所)》2016年硕士论文　论文类型：学位论文

【摘要】：人造信标提高了自适应光学天文望远镜系统的天空覆盖率,弥补了自然信标的不足。相对瑞利信标而言,人造钠信标具有更好的性能,更加适用于大口径天文望远镜系统,是未来人造信标的发展方向。由于大气湍流、噪声以及系统的几何位置关系等因素的影响,系统探测到的人造钠信标光斑会出现扩展、拉长、信噪比低等现象,降低了波前探测的精度。因此,研究如何提高人造钠信标波前探测的精度具有重要的意义。本文基于自适应光学天文望远镜系统,从理论上介绍了人造钠信标的产生机理以及使用夏克-哈特曼波前传感器对信标进行波前探测的过程。本文详细分析了造成钠信标光斑扩展与拉长的原因,以及光斑的不同信噪比、扩展度与拉长度对波前探测的影响。介绍了多种提高系统的波前探测精度的方式,其中提高对光斑的质心提取精度是一种高效而便捷的方法。本文的重点是探究在不同的光斑情况下,哪一种质心提取算法的精度最高。为此,本文选取了五种算法,即基本质心法、高斯加权质心法、强加权质心法(分为幂次强加权、加法强加权、乘法强加权三种)、阈值质心法和距离质心法。首先仿真出三类光斑(不同信噪比、不同扩展度以及不同拉长度),用上述五种算法进行质心提取,通过对比各算法的提取误差,可以得出初步结论。接着对上述过程进行进一步重复性的仿真,通过统计数据可以得出结论:对于良好的信噪比与非扩展拉长的光斑,各算法的精度均较高;对于扩展与拉长光斑而言,选择加权质心法优于其他算法;对于噪声影响的光斑,需要根据不同的信噪比情况选择合适的参数与算法。最后,考虑到实际情况是噪声、扩展与拉长多因素并存的情况,对三种情况并存的光斑进行了质心提取算法,以得到更符合实际情况的结论。为了验证仿真结论的准确性,本文最后对不同信噪比与不同扩展度情况的光斑下进行了实验研究。用五种算法对各光斑阵列进行波前复原,对比复原的精度,最终验证了仿真结果与实验结果基本一致。本文通过理论、仿真与实验的研究可知,对于不同信噪比、扩展、拉长光斑,选择加权质心法(高斯加权质心法与强加权质心法)能提高质心探测精度。最后,本文对未来的质心提取进行了展望,可以针对同一光斑阵列中,具有不同种类的光斑类型的情况采用不同的算法,以提高系统的波前探测精度。
[Abstract]:Artificial beacons improve the sky coverage of adaptive optical telescope systems and make up for the deficiencies of natural beacons. Compared with Rayleigh beacons, artificial sodium beacons have better performance and are more suitable for large aperture astronomical telescope systems. It is the development direction of artificial beacons in the future. Due to the influence of atmospheric turbulence, noise and the geometric position relationship of the system, the spot of artificial sodium beacon detected by the system will be expanded, elongated, and the signal-to-noise ratio will be low. Therefore, it is of great significance to study how to improve the accuracy of wavefront detection by artificial sodium beacons. This paper is based on the adaptive optical telescope system. The production mechanism of artificial sodium beacons and the process of wavefront detection using Shack-Hartmann wavefront sensor are introduced theoretically. The causes of the expansion and elongation of the spot in sodium beacons are analyzed in detail in this paper. The influence of different signal-to-noise ratio (SNR), extensibility and stretch length of light spot on wavefront detection is introduced, and several ways to improve the precision of wave-front detection of the system are introduced. It is an efficient and convenient method to improve the accuracy of centroid extraction for spot. The emphasis of this paper is to find out which algorithm has the highest precision in different spot cases. Therefore, five algorithms are selected in this paper. That is, basic centroid method, Gao Si weighted centroid method, strongly weighted centroid method (divided into power strongly weighted, additive strongly weighted, multiplicative strongly weighted, threshold centroid and distance centroid). The centroid is extracted with the above five algorithms with different extension degree and different drawing length. By comparing the extraction errors of each algorithm, we can draw a preliminary conclusion. From the statistical data, we can draw a conclusion that the accuracy of each algorithm is higher for the spot with good SNR and non-extended stretching; for the extended and elongated spot, the weighted centroid method is superior to other algorithms; for the speckle affected by noise, the weighted centroid method is better than other algorithms. It is necessary to select appropriate parameters and algorithms according to different signal-to-noise ratio. Finally, considering that the actual situation is noise, expansion and elongation co-exist, the centroid extraction algorithm is proposed for the spot with three different conditions. In order to verify the accuracy of the simulation results, the experiments are carried out under different signal to noise ratio (SNR) and different spreading degrees. Five algorithms are used to restore the wavefront of each spot array. Compared with the precision of restoration, the simulation results are basically consistent with the experimental results. Through the theoretical, simulation and experimental studies, we can see that for different SNR, extended, elongated spot, The accuracy of centroid detection can be improved by choosing weighted centroid method (Gao Si weighted centroid method and strongly weighted centroid method). Finally, the future centroid extraction is prospected, which can be applied to the same spot array. Different algorithms are used to improve the wavefront detection accuracy of the system with different types of spot types.
【学位授予单位】：中国科学院研究生院(光电技术研究所)
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TH751

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