本文關(guān)鍵詞： 自適應(yīng)光學(xué) 液晶波前校正器 大氣湍流 角錐波前探測器　出處：《中國科學(xué)院長春光學(xué)精密機械與物理研究所》2017年博士論文　論文類型：學(xué)位論文

【摘要】：眾所周知,自適應(yīng)光學(xué)系統(tǒng)可以對望遠鏡接收的動態(tài)畸變波前進行實時探測校正,恢復(fù)其自身的光學(xué)衍射極限成像分辨率。由于天文、軍事等領(lǐng)域的發(fā)展趨勢,要求望遠鏡有能力對暗弱目標進行高清晰度成像。傳統(tǒng)的哈特曼波前探測器將入射光分為數(shù)十甚至數(shù)百個子光束的探測原理導(dǎo)致其信噪比低,無論望遠鏡口徑多大,哈特曼探測器的極限探測星等最高為5.5星等,無法探測暗弱目標。近年開始嘗試應(yīng)用的角錐波前探測器對暗弱目標的探測能力要強于哈特曼波前探測器。角錐探測器是將入射光束會聚在角錐棱鏡頂點,使光束分為4個子光束形成4個探測器入瞳孔徑的像,波前畸變使角錐錐尖光斑亮度分布發(fā)生變化或整體偏移,從而使4個光瞳像能量分布不均,光瞳像內(nèi)部亮度分布也不均,根據(jù)4個光瞳像對應(yīng)像素上的亮度歸一化差異可以計算得到與波前局部斜率正相關(guān)的響應(yīng)信號,進而解算畸變波前。然而角錐探測器動態(tài)范圍較小,當波前畸變較大,尤其是傾斜量較大時,光斑在角錐錐尖上的偏移量過大,造成只出現(xiàn)一個光瞳像而其他三個光瞳像亮度過低,或光瞳像局部亮度過低,導(dǎo)致無法解算波前。由于角錐波前探測器的動態(tài)范圍小,目前只能應(yīng)用于閉環(huán)控制系統(tǒng),尚未有報道使用角錐波前探測器的工程化開環(huán)自適應(yīng)光學(xué)系統(tǒng)。而開環(huán)控制模式是自適應(yīng)光學(xué)的發(fā)展趨勢,其中的波前探測器直接接收望遠鏡的入射波前,要求波前探測器動態(tài)范圍要大、探測精度更高。針對角錐探測器動態(tài)范圍小的問題,考慮將光斑在角錐錐尖上的偏移量不同轉(zhuǎn)變?yōu)楣獍咴谒腻F面上曝光時間不同來定量減小四個光瞳像的亮度差異,擴展動態(tài)范圍。設(shè)計了快反鏡調(diào)制棱鏡錐尖上的光斑沿圓軌跡運動使4個光瞳像依次出現(xiàn);由于入射波前傾斜導(dǎo)致圓軌跡中心偏離棱鏡錐尖,光斑在各錐面上的運動時間不同,各光瞳像的曝光時間也不同,從而調(diào)制其亮度,使原本亮度過低的光瞳像亮度提高至可被探測,且光瞳像亮度差異與畸變引起的圓軌跡中心偏移成正比,原來的波前重構(gòu)方法仍然適用。上述調(diào)制型角錐探測器的動態(tài)范圍理論上可從原來的1λ擴大至12λ(λ=780nm),滿足實際大氣湍流的探測需求。但調(diào)制型角錐探測器中又產(chǎn)生了如下問題:光斑經(jīng)過角錐棱邊時,由于光瞳像光場疊加引入四條亮帶,造成重構(gòu)波前的高階誤差;亮帶亮度值是背底噪聲的10倍,因此無法用閾值法直接扣除。另外,光瞳像因調(diào)制發(fā)生的位置偏移不能超過3像素,否則光瞳像邊緣發(fā)生彌散,無法精確定位,而任一光瞳像定位不準確都會導(dǎo)致對應(yīng)像素的錯位誤差。同時,由于棱鏡引入的軸向色差以及光瞳孔徑邊緣衍射形成的光暈,也會使光瞳像邊緣形成幾個到十幾個像素的彌散,產(chǎn)生光瞳像定位誤差;另外,大像差輸入使原響應(yīng)矩陣計算過程中的小像差近似條件不再適用,同時調(diào)制過程導(dǎo)致光瞳像亮度差異與波前畸變對應(yīng)關(guān)系發(fā)生變化,需要重新計算調(diào)制型角錐探測器的響應(yīng)矩陣。根據(jù)zemax軟件仿真設(shè)計結(jié)果,以光瞳像在對角方向內(nèi)外邊緣亮度值差異為判據(jù),對角錐探測器進行了精密裝調(diào),獲得了邊緣最銳利、內(nèi)外邊緣點共線的光瞳像,光瞳像對角方向內(nèi)外邊緣亮度值差異為7.84%,調(diào)制過程引起的光瞳像振動幅度小于1像素。針對光場疊加引入的亮帶,分析了光瞳間距不同時亮帶對光瞳像內(nèi)部亮度分布的影響,設(shè)計并調(diào)節(jié)光瞳像以3.8倍半徑的中心距等距分布,此時可以忽略光瞳像間亮帶對探測信號的影響。使用雙角錐棱鏡替代單角錐棱鏡,消除了單棱鏡色散效應(yīng)以及色散導(dǎo)致的光瞳像邊緣模糊,同時降低了棱鏡加工難度。分析了光瞳像邊緣亮度分布特征,發(fā)現(xiàn)對光瞳像邊緣亮度極大值點定位并不能對光瞳像邊緣精確定位。提出對光瞳像邊緣亮度梯度極大值進行定位,定位精度達到像素級別;然后利用相關(guān)算法二次標定光瞳像中心坐標,令高像素密度的液晶校正器產(chǎn)生包含10個精細同心圓的靶圖,此時光瞳像內(nèi)部亮度分布也為同心圓,計算光瞳像中心坐標在粗定位坐標附近振蕩時,對應(yīng)的光瞳像同心靶圖的互相關(guān)度,對光瞳像中心二次定位,精度提高至亞像素級別。搭建實驗室靜態(tài)像差探測校正平臺,在系統(tǒng)光瞳與光瞳像嚴格共軛的前提下,光瞳像精確提取使開環(huán)探測誤差相較光瞳像粗定位系統(tǒng)減小60%,閉環(huán)校正收斂速度加快,閉環(huán)校正殘差減小15%。分析發(fā)現(xiàn)調(diào)制型角錐探測器響應(yīng)矩陣相當于在無調(diào)制探測信號上疊加了由傾斜調(diào)制引入的調(diào)制多項式,其物理意義相當于調(diào)制導(dǎo)致的畸變響應(yīng)信號幅度衰減。大像差輸入情況下,響應(yīng)矩陣中包含的三角函數(shù)項會發(fā)生高頻振蕩,導(dǎo)致無法精確計算;通過坐標歸一化,使衰減項中三角函數(shù)自變量閾值變小,抑制了衰減項振蕩。對響應(yīng)信號本身包含的三角函數(shù)項,由于其自變量顯含Zernike多項式,使用小系數(shù)Zernike基底抑制其在大像差輸入情況下的振蕩,并在重構(gòu)過程中施加增益以保證響應(yīng)矩陣幅值。計算了輸入像差為10λ時,調(diào)制型角錐探測器對35項Zernike模式的響應(yīng)矩陣。使用角錐探測器和Zygo干涉儀搭建了探測器精度驗證光路,在精密裝調(diào)和光瞳像精確定位的基礎(chǔ)上,對不同幅度的包含35項Zernike模式的隨機靜態(tài)像差進行探測。探測結(jié)果顯示,使用開環(huán)響應(yīng)矩陣與傳統(tǒng)響應(yīng)矩陣相比,探測器探測誤差RMS值減小50%,對不同幅度像差的探測誤差RMS值均小于λ/20,基本滿足開環(huán)系統(tǒng)探測需求。本論文獲得的結(jié)論證明,通過擴展角錐波前探測器動態(tài)范圍的研究,實現(xiàn)了探測動態(tài)范圍滿足實際大氣湍流探測需求的角錐波前探測器。同時,該探測器具備在自適應(yīng)光學(xué)系統(tǒng)中對大像差輸入的高精度探測能力,探測誤差RMS值小于λ/20。該研究將角錐波前探測器的應(yīng)用范圍從閉環(huán)系統(tǒng)擴展至開環(huán)系統(tǒng),對提高自適應(yīng)光學(xué)系統(tǒng)極限探測星等,實現(xiàn)對暗弱目標的高精度成像起到積極的推進作用。
[Abstract]:As everyone knows, the adaptive optics system on dynamic wavefront telescope received real-time detection correction, recovery of optical diffraction limit imaging resolution of its own. The development trend of astronomy, military and other fields, have the ability to request telescope high-resolution imaging of faint objects. Hartmann wavefront sensor divides the incident light into the traditional detection principle of dozens or even hundreds of sub beams due to the low signal-to-noise ratio, no matter how large aperture telescope limit Hartmann detector is the highest detectable magnitude 5.5 magnitude, to detect faint objects. In recent years, began to try to apply the pyramid wavefront detector faint target detection ability is stronger than Hartmann. Pyramid wavefront detector detector is an incoming light beam converged at the prism vertex so, the beam is divided into 4 sub beams form 4 detectors like the pupil aperture, the wavefront distortion Pyramid tip spot brightness distribution changes or the whole migration, thus making the 4 pupil like uneven distribution of energy within the pupil image brightness distribution is not uniform, according to the 4 pupil image brightness normalized difference corresponding pixel can be calculated positive correlation with wavefront local slope of the response signal, then calculates the wavefront aberration. However pyramid detector dynamic range is small, when the wavefront distortion, especially tilt when a large amount of spots in the pyramid cone offset on the tip is too large, resulting in only one pupil like the other three pupil image brightness is too low, or pupil like local brightness is too low, leading to the solution due to the dynamic range of wavefront. Pyramid wavefront detector, at present can only be applied to the closed-loop control system, have not been reported using pyramid wavefront detector engineering open-loop adaptive optics system. The open-loop control mode is adaptive optics The development trend of the incident wavefront wavefront detector which receives the telescope, wavefront detector dynamic range is bigger, higher detection accuracy. The pyramid detector dynamic range small, considering the spot in the pyramid cone offset on the tip into a spot in the four different exposure time of different cone to quantitative reduced four light the pupil like brightness difference, extended dynamic range. The design of fast steering mirror modulation spot on the tip of the cone prism along the circular track of the 4 pupil like one; because the incident led to the circular wavefront tilt center deviation prism cone, the cone on the spot in the exercise time is different, each pupil as the exposure time is different, so as to modulate the brightness, the pupil brightness as low as brightness can be improved to detect, track and circle center offset pupil image brightness difference and distortion caused by proportional to the original Wavefront reconstruction method is still applicable. The dynamic range of the theory of modulation type detector on the pyramid can be expanded from the original 1 to 12 lambda lambda (lambda =780nm), to meet the demand of actual detection of atmospheric turbulence. But the modulation type detector and pyramid problems were as follows: after the spot edge pyramid, the pupil like light field the superposition of four bright bands, high order error caused by wavefront reconstruction; bright band brightness value is 10 times the background noise, and therefore can not be directly deducted by threshold method. In addition, the pupil like due to offset not modulation occurred more than 3 pixels, or pupil image edge diffusion, precise positioning, and any pupil like inaccurate positioning error will lead to the corresponding pixel. At the same time, due to the introduction of axial chromatic aberration and prism light aperture edge diffraction halo formation, also can make the pupil image edge to form a few dozen pixel diffusion, Have a pupil like positioning error; in addition, large aberration input makes small aberration original response matrix calculation of the approximation is no longer applicable, at the same time modulation process causes the pupil image brightness difference and wavefront distortion of corresponding change, need to re calculate the response matrix modulation type pyramid detector. According to the simulation results of ZEMAX software design, to light the pupil like in the diagonal direction of inner and outer edge brightness value difference criterion, diagonal cone detector precision alignment, obtained the most sharp edge, inner and outer edge of collinear pupil image, pupil image edge and diagonal brightness value difference is 7.84%, the pupil modulation process of image due to vibration amplitude is less than 1 pixels. The bright band optical field superposition is introduced, analyzed and pupil spacing is the bright band of pupil influence of image brightness distribution, design and adjust as 3.8 times the radius of the center distance and pupil distance distribution, This can ignore the pupil image between bright band effects on signal detection. Instead of a single prism using double prism, eliminating the pupil single prism dispersion and dispersion causes like edge blur, while reducing the processing difficulty. Analysis of the prism pupil image edge brightness distribution characteristics, found on the pupil image edge the maximum brightness is not on the point positioning pupil image edge accurately. The positioning of the pupil image edge brightness gradient maximum, the positioning accuracy of the pixel level; and then use the algorithm two calibration pupil image center coordinates, so that the liquid crystal corrector high pixel density which contains 10 fine concentric target map at this time, the pupil like internal radiance distribution for concentric circles, calculate pupil image coordinates of the center of the coarse positioning coordinates of oscillation, the pupil image corresponding to the target map concentric degree of cross-correlation, the pupil image center two To improve the positioning precision, the sub-pixel level was set up. The laboratory static correction of aberration detection platform, in the premise of pupil and pupil like strictly conjugate, pupil image accurate extraction of the open-loop detection error compared with the pupil image coarse positioning system is reduced by 60%, with fast convergence speed closed-loop correction, reduce the residual 15%. analysis found that modulation pyramid type detector response matrix is equivalent to no modulation detection signal superimposed on the modulation polynomial introduced by the tilt modulation closed-loop, the distortion of its physical meaning is equivalent to the modulation induced response signal amplitude attenuation. Large aberration input, in response to the trigonometric terms contained in the matrix will lead to high frequency oscillation, through precise calculation; coordinate normalization, the attenuation of trigonometric function in variable threshold decreases, inhibited the decay oscillation. The trigonometric function for the response signal itself contains, due to the self change The amount of explicit Zernike polynomial in the reduction of large aberration input on the oscillation using small coefficient Zernike substrate, and in the process of reconstruction is applied to ensure the gain of the response matrix and compute the input amplitude. Aberration is about 10. When the response matrix modulation pyramid detector for 35 Zernike modes. The interferometer is built to verify the accuracy of the detector the light path using pyramid detector and Zygo, and the pupil as the basis of accurate positioning in precision, static random aberration on different amplitude contains 35 Zernike mode detection. The detection results show that using the open-loop response matrix and traditional response matrix compared to RMS detector error detection error decreases 50%, RMS for different amplitude aberration values were less than lambda /20, open loop system basically meet the detection requirements. The article concludes that, through the research to extend the dynamic range of pyramid wavefront sensor, real The dynamic detection range to meet the actual needs of the atmospheric turbulence detection pyramid wavefront sensor. At the same time, the detector has a high precision detection ability of input aberration in an adaptive optical system, detection error RMS value is less than lambda /20. the study will be used to pyramid wavefront sensor range from the closed-loop system to the open-loop system, to improve the magnitude of adaptive optical system, realize high precision imaging of faint objects play a positive role in promoting.

【學(xué)位授予單位】：中國科學(xué)院長春光學(xué)精密機械與物理研究所
【學(xué)位級別】：博士
【學(xué)位授予年份】：2017
【分類號】：TH74

【參考文獻】

相關(guān)期刊論文 前10條

1 王勝千;魏凱;鄭文佳;饒長輝;;First light on an adaptive optics system using a non-modulation pyramid wavefront sensor for a 1.8 m telescope[J];Chinese Optics Letters;2016年10期

2 宣麗;李大禹;劉永剛;;液晶自適應(yīng)光學(xué)在天文學(xué)研究中的應(yīng)用展望[J];液晶與顯示;2015年01期

3 劉超;胡立發(fā);穆全全;曹召良;胡紅斌;張杏云;蘆永軍;宣麗;;用于開環(huán)液晶自適應(yīng)光學(xué)系統(tǒng)的模式預(yù)測技術(shù)研究[J];物理學(xué)報;2012年12期

4 劉超;胡立發(fā);曹召良;穆全全;彭增輝;宣麗;;快速響應(yīng)的硅基純相位液晶器件對動態(tài)大氣湍流波前的校正能力研究[J];物理學(xué)報;2012年08期

5 曹召良;李小平;宣麗;穆全全;胡立發(fā);彭增輝;劉永剛;姚麗雙;;液晶自適應(yīng)光學(xué)的研究進展[J];中國光學(xué);2012年01期

6 王建新;白福忠;寧禹;黃林海;姜文漢;;無調(diào)制兩面錐波前傳感器的衍射理論分析和數(shù)值仿真[J];物理學(xué)報;2011年02期

7 陳浩;宣麗;胡立發(fā);曹召良;穆全全;;1200mm望遠鏡開環(huán)液晶自適應(yīng)光學(xué)系統(tǒng)設(shè)計[J];光學(xué)精密工程;2010年01期

8 朱能鴻;陳欣揚;周丹;曹建軍;;利用四棱錐傳感器檢測光學(xué)拼接鏡的法向光程差[J];傳感技術(shù)學(xué)報;2009年03期

9 陳欣揚;朱能鴻;;基于四棱錐傳感器的波前檢測仿真設(shè)計[J];天文學(xué)進展;2006年04期

10 饒長輝;姜文漢;張雨東;凌寧;李梅;張學(xué)軍;李彥英;官春林;陳東紅;沈鋒;廖周;湯國茂;周璐春;王彩霞;張昂;吳碧琳;魏凱;;云南天文臺1．2m望遠鏡61單元自適應(yīng)光學(xué)系統(tǒng)[J];量子電子學(xué)報;2006年03期

，

本文編號：1446370