本文關(guān)鍵詞： 自適應(yīng)光學(xué) 人造鈉信標(biāo) 波前探測(cè) 光斑形態(tài) 質(zhì)心提取算法　出處：《中國(guó)科學(xué)院研究生院(光電技術(shù)研究所)》2016年碩士論文　論文類(lèi)型：學(xué)位論文

【摘要】：人造信標(biāo)提高了自適應(yīng)光學(xué)天文望遠(yuǎn)鏡系統(tǒng)的天空覆蓋率,彌補(bǔ)了自然信標(biāo)的不足。相對(duì)瑞利信標(biāo)而言,人造鈉信標(biāo)具有更好的性能,更加適用于大口徑天文望遠(yuǎn)鏡系統(tǒng),是未來(lái)人造信標(biāo)的發(fā)展方向。由于大氣湍流、噪聲以及系統(tǒng)的幾何位置關(guān)系等因素的影響,系統(tǒng)探測(cè)到的人造鈉信標(biāo)光斑會(huì)出現(xiàn)擴(kuò)展、拉長(zhǎng)、信噪比低等現(xiàn)象,降低了波前探測(cè)的精度。因此,研究如何提高人造鈉信標(biāo)波前探測(cè)的精度具有重要的意義。本文基于自適應(yīng)光學(xué)天文望遠(yuǎn)鏡系統(tǒng),從理論上介紹了人造鈉信標(biāo)的產(chǎn)生機(jī)理以及使用夏克-哈特曼波前傳感器對(duì)信標(biāo)進(jìn)行波前探測(cè)的過(guò)程。本文詳細(xì)分析了造成鈉信標(biāo)光斑擴(kuò)展與拉長(zhǎng)的原因,以及光斑的不同信噪比、擴(kuò)展度與拉長(zhǎng)度對(duì)波前探測(cè)的影響。介紹了多種提高系統(tǒng)的波前探測(cè)精度的方式,其中提高對(duì)光斑的質(zhì)心提取精度是一種高效而便捷的方法。本文的重點(diǎn)是探究在不同的光斑情況下,哪一種質(zhì)心提取算法的精度最高。為此,本文選取了五種算法,即基本質(zhì)心法、高斯加權(quán)質(zhì)心法、強(qiáng)加權(quán)質(zhì)心法(分為冪次強(qiáng)加權(quán)、加法強(qiáng)加權(quán)、乘法強(qiáng)加權(quán)三種)、閾值質(zhì)心法和距離質(zhì)心法。首先仿真出三類(lèi)光斑(不同信噪比、不同擴(kuò)展度以及不同拉長(zhǎng)度),用上述五種算法進(jìn)行質(zhì)心提取,通過(guò)對(duì)比各算法的提取誤差,可以得出初步結(jié)論。接著對(duì)上述過(guò)程進(jìn)行進(jìn)一步重復(fù)性的仿真,通過(guò)統(tǒng)計(jì)數(shù)據(jù)可以得出結(jié)論:對(duì)于良好的信噪比與非擴(kuò)展拉長(zhǎng)的光斑,各算法的精度均較高;對(duì)于擴(kuò)展與拉長(zhǎng)光斑而言,選擇加權(quán)質(zhì)心法優(yōu)于其他算法;對(duì)于噪聲影響的光斑,需要根據(jù)不同的信噪比情況選擇合適的參數(shù)與算法。最后,考慮到實(shí)際情況是噪聲、擴(kuò)展與拉長(zhǎng)多因素并存的情況,對(duì)三種情況并存的光斑進(jìn)行了質(zhì)心提取算法,以得到更符合實(shí)際情況的結(jié)論。為了驗(yàn)證仿真結(jié)論的準(zhǔn)確性,本文最后對(duì)不同信噪比與不同擴(kuò)展度情況的光斑下進(jìn)行了實(shí)驗(yàn)研究。用五種算法對(duì)各光斑陣列進(jìn)行波前復(fù)原,對(duì)比復(fù)原的精度,最終驗(yàn)證了仿真結(jié)果與實(shí)驗(yàn)結(jié)果基本一致。本文通過(guò)理論、仿真與實(shí)驗(yàn)的研究可知,對(duì)于不同信噪比、擴(kuò)展、拉長(zhǎng)光斑,選擇加權(quán)質(zhì)心法(高斯加權(quán)質(zhì)心法與強(qiáng)加權(quán)質(zhì)心法)能提高質(zhì)心探測(cè)精度。最后,本文對(duì)未來(lái)的質(zhì)心提取進(jìn)行了展望,可以針對(duì)同一光斑陣列中,具有不同種類(lèi)的光斑類(lèi)型的情況采用不同的算法,以提高系統(tǒng)的波前探測(cè)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.
【學(xué)位授予單位】：中國(guó)科學(xué)院研究生院(光電技術(shù)研究所)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2016
【分類(lèi)號(hào)】：TH751

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