本文關(guān)鍵詞： 自適應(yīng)光學(xué) 激光導(dǎo)星 動態(tài)聚焦系統(tǒng) 大氣非等暈 傾斜探測 液晶波前校正器 響應(yīng)矩陣　出處：《中國科學(xué)院研究生院(長春光學(xué)精密機械與物理研究所)》2016年博士論文　論文類型：學(xué)位論文

【摘要】：自適應(yīng)光學(xué)成像技術(shù)通過實時探測和校正大氣湍流引起的波前畸變,能夠恢復(fù)望遠(yuǎn)鏡對空間目標(biāo)的高分辨成像能力。但是往往被觀測目標(biāo)很暗,自適應(yīng)光學(xué)系統(tǒng)無法分解出足夠的波前探測能量限制了其成像能力。為此人們提出了人造激光導(dǎo)星技術(shù)來提高自適應(yīng)光學(xué)系統(tǒng)對暗目標(biāo)探測能力的方法。本文根據(jù)瑞利導(dǎo)星比較容易實現(xiàn),所要求的激光器已有市售商品,深入研究了基于瑞利導(dǎo)星的自適應(yīng)光學(xué)技術(shù)。瑞利導(dǎo)星采用自適應(yīng)光學(xué)系統(tǒng)旁的激光發(fā)射系統(tǒng)向被觀測目標(biāo)方向發(fā)射脈沖激光,激光脈沖在10~20km處形成所謂的“瑞利導(dǎo)星”。瑞利導(dǎo)星自適應(yīng)光學(xué)系統(tǒng)的工作原理,是自適應(yīng)光學(xué)系統(tǒng)中的波前探測器接收瑞利導(dǎo)星的后向散射光給出波前畸變信號。主要有以下問題:1、瑞利導(dǎo)星的散射層采樣厚度一般限制為1~2km,導(dǎo)致此范圍以外的光能量不能被接收,因而瑞利導(dǎo)星的波前探測能量比較低;2、由于瑞利導(dǎo)星工作高度相對被成像目標(biāo)來說低得多,對望遠(yuǎn)鏡形成錐形光通道而不像后者形成圓柱形光通道,因此瑞利導(dǎo)星不能對觀測目標(biāo)的整個大氣通道進(jìn)行全部采樣,導(dǎo)致波前探測誤差較大;3、瑞利導(dǎo)星不能提供望遠(yuǎn)鏡口徑上波前傾斜信息。本研究針對波前探測能量低的問題,設(shè)計了動態(tài)聚焦系統(tǒng),利用動態(tài)元件的實時移動使激光在任何高度處都理想成像;該動態(tài)聚焦系統(tǒng)可以實現(xiàn)10km厚度的瑞利散射層探測,在13km高度處的瑞利導(dǎo)星亮度可高達(dá)2.1視星等,相比于1km的采樣厚度,理論上波前探測能量可以提高7.3倍。針對波前探測精度低的問題,采用五顆導(dǎo)星降低聚焦非等暈誤差,理論上對于10米望遠(yuǎn)鏡,采用5顆位于10km處的瑞利導(dǎo)星,其聚焦非等暈誤差會下降約34%。據(jù)此提出利用準(zhǔn)直透鏡陣列和遠(yuǎn)心光路實現(xiàn)多導(dǎo)星波前探測系統(tǒng)的設(shè)計。針對波前整體傾斜探測問題,采用被觀測目標(biāo)的400nm~600nm范圍的光能量進(jìn)行傾斜探測。對于1.23m望遠(yuǎn)鏡對觀測目標(biāo)進(jìn)行2倍衍射極限成像時,且高階校正后殘差為1rad時,波前傾斜殘差需小于0.0266″,此時9等星亮度的觀測目標(biāo)即可滿足探測要求。說明使用瑞利導(dǎo)星可使自適應(yīng)光學(xué)系統(tǒng)的觀測極限星等由5視星等提高到9視星等。最后,設(shè)計了一套瑞利導(dǎo)星自適應(yīng)光學(xué)系統(tǒng),解決了瑞利導(dǎo)星有限高度對望遠(yuǎn)鏡成像焦點和無限遠(yuǎn)成像焦點不重合而產(chǎn)生的離焦問題。為了提高系統(tǒng)的校正精度,根據(jù)液晶校正器的工作機制,分析了由于有限驅(qū)動電壓和灰度級引起的器件誤差,并提出優(yōu)化方案;同時提出一種提高響應(yīng)矩陣測量精度的方法,該方法針對不同Zernike模式特定其模式系數(shù),使每一項Zernike模式波面相對于256×256像素數(shù)液晶波前校正器的量化級次都達(dá)到10級;同時利用最小二乘法消除測量過程中的隨機噪聲。該方法相對于改進(jìn)前的響應(yīng)矩陣測量方法,使自適應(yīng)校正后的圖像功率譜顯著提高,部分頻段提高有2~3倍。本論文屬于瑞利導(dǎo)星自適應(yīng)光學(xué)系統(tǒng)的開創(chuàng)性工作,經(jīng)過波前探測能量、波前探測精度以及校正精度方面的改進(jìn),展示出了瑞利導(dǎo)星可以應(yīng)用于大口徑望遠(yuǎn)鏡的自適應(yīng)光學(xué)系統(tǒng)的潛力。論文的研究成果對瑞利導(dǎo)星自適應(yīng)光學(xué)的應(yīng)用做出了一定的貢獻(xiàn)。
[Abstract]:Adaptive optical imaging technology through real-time detection and correction of wavefront aberration caused by atmospheric turbulence, can restore the telescope for space target high resolution imaging ability. But the target is often very dark, adaptive optical system cannot decompose enough energy wavefront detection limit its imaging capability. So people proposed artificial laser guide star technology to improve the method of adaptive optical system detection capability of the dark target. Based on the Rayleigh guide star is relatively easy to achieve the required commodity sale has been deeply studied, laser, adaptive optics technology based on Rayleigh guide star. Rayleigh guide star adaptive optical system by the laser system to the observed target emission direction of pulsed laser, laser the pulse at 10~20km to form a so-called "Rayleigh guide star". The working principle of Rayleigh guide star adaptive optics system, adaptive Wavefront detector in optical system receives the Rayleigh backscattering light guide star gives the wavefront distortion signal. Mainly has the following problems: 1, Rayleigh scattering layer star sampling thickness is generally restricted to 1~2km, resulting in light energy can not be outside this range is received, the Rayleigh guide star wavefront sensing energy is relatively low; 2. Because the work is relatively high Rayleigh guide star imaging target is much lower, to form a conical telescope optical channel rather than the latter to form a cylindrical optical channel, therefore not on Rayleigh guide star target in the atmospheric channel of all samples lead to wavefront detection error is big; 3, Rayleigh guide star cannot provide the telescope on the wavefront tilt based on the information. The problem of low energy wavefront detection is designed, dynamic focusing system, the use of mobile real-time dynamic elements at any height are the ideal imaging laser makes the dynamic; 鑱氱劍緋葷粺鍙互瀹炵幇10km鍘氬害鐨勭憺鍒╂暎灝勫眰鎺㈡祴,鍦，

本文編號：1474584