發(fā)布時間：2018-05-21 00:34

  本文選題：衍射傳輸 + 光束質(zhì)量�。� 參考：《中國科學院研究生院(長春光學精密機械與物理研究所)》2016年博士論文

【摘要】：將高功率激光聚焦到遠距離目標,獲得高能量密度光斑分布,對國防、工業(yè)加工、制造領(lǐng)域有較大價值。從激光發(fā)射系統(tǒng)設(shè)計,到光場自由空間傳輸,再到激光聚焦光斑的反饋評價,涉及到大量建模、參數(shù)選取以及結(jié)構(gòu)設(shè)計問題,通過仿真方法對系統(tǒng)進行合理設(shè)計與優(yōu)化,能夠節(jié)省大量成本與時間上的耗費。衍射光學是現(xiàn)代光學工程的基本方法之一,利用衍射傳輸能夠滿足激光遠距離聚焦傳輸?shù)姆抡嬉蟆１疚脑诩す獾难苌鋫鬏斃碚摶A(chǔ)上,提出了適合激光聚焦仿真的改進算法,對仿真中激光的模式以及部分相干問題進行詳細討論,結(jié)合具體的聚焦系統(tǒng)設(shè)計,仿真分析了各種系統(tǒng)參數(shù)對遠距離聚焦的影響并進行實驗驗證。另外提出了基于回波散斑的激光聚焦光斑反饋評價方法,能夠?qū)劢钩叨冗M行高精度監(jiān)視,使本文涵蓋了激光發(fā)射、傳輸與反饋評價的仿真閉環(huán),達到對系統(tǒng)工作性能的全面分析與評估。本文包含的主要工作如下:1.在標量衍射理論、激光光束傳輸基本理論以及現(xiàn)有的激光光束質(zhì)量評價指標基礎(chǔ)上,提出了對不同狀態(tài)(初始光場分布、光束的相干性、傳輸環(huán)境等)的激光光束傳輸進行仿真的算法。首先,為了仿真光束經(jīng)理想光學系統(tǒng)傳輸,在Collins衍射積分與線性調(diào)頻Fourier變換(CFT)基礎(chǔ)上,提出了寬窗口角譜算法(WWAS)。CFT的應(yīng)用可以使輸入輸出空間域與空間頻率域采樣分離,在選取大計算窗口時不增加算法計算負擔,解決了傳統(tǒng)角譜法在仿真激光遠距離傳輸時信噪比迅速下降的問題,而且輸入與輸出空間域的獨立使得算法采樣更加靈活。另外,基于信噪比分析方法對WWAS算法采樣條件進行推導與驗證。在自由空間傳輸條件下,對比了wwas算法與其它角譜法的傳輸效果,給出了該算法的優(yōu)勢。其次,為了仿真多模部分相干激光光束傳輸問題,提出了基于光強分布測量進行激光模式分解的線性方程組方法,利用該方法不但能夠獲得相干模式系數(shù)的能量分布,而且通過有限次縱向光強分布測量,得到不同模式之間的相關(guān)性差異。仿真中采用構(gòu)造光束的方法對理論進行了驗證。已知激光模式分布后,提出了一種部分相干激光的仿真方法,在兼顧了fft算法的高效性同時,保證了部分相干光束傳輸仿真的精度。2.在光束傳輸算法基礎(chǔ)上,對激光遠距離聚焦系統(tǒng)聚焦特性進行分析。首先利用zemax軟件,設(shè)計了激光遠距離聚焦系統(tǒng),對系統(tǒng)的幾何參數(shù)、激光參數(shù)、焦移量以及調(diào)焦曲線進行計算。利用光束傳輸算法分析了系統(tǒng)孔徑截斷帶來的衍射損耗與聚焦光斑能量密度分布變化,與廣義m2因子的評價方法進行對比分析,給出廣義m2因子在受到孔徑衍射聚焦系統(tǒng)中的評價作用。對于聚焦系統(tǒng)公差與調(diào)焦補償誤差,在像差衍射理論基礎(chǔ)上,提出了zemax與matlab聯(lián)合仿真的方法,zemax為光束傳輸算法提供出瞳像差,仿真計算得到聚焦光斑分布,可以分析公差分配是否合理,并給出合理的補償方案。隨后,采用實驗方法對聚焦光斑能量分布、光斑形態(tài)進行測量,驗證了仿真分析的正確性。另外,理論分析了大氣湍流對激光光束傳輸?shù)挠绊?并且對激光經(jīng)大氣擾動后m2因子的變化進行研究,給出了在無自適應(yīng)系統(tǒng)時激光光束質(zhì)量與大氣擾動間存在的權(quán)衡關(guān)系。3.研究了基于目標回波散斑統(tǒng)計特性的激光聚焦光斑尺度監(jiān)視與反饋技術(shù)。對于靜態(tài)或緩慢運動目標,提出了兩種散斑評價因子對激光聚焦光斑尺度進行評價:二值化散斑自相關(guān)評價因子(csam)由散斑的自相關(guān)函數(shù)計算得到,隨光斑尺減小而增大;二值化散斑邊緣積分(csei)評價因子對回波散斑的像進行二值化與邊緣提取操作,csei因子隨聚焦光斑尺度減小而減小;本文仿真分析了接收系統(tǒng)參數(shù)、目標粗糙程度、有限數(shù)據(jù)長度等因素對兩種評價因子的精度影響,通過實驗驗證了理論分析結(jié)果,證明了兩種評價因子對聚焦光斑的評估能力。對于快速運動目標,提出了利用雙探測器信號相關(guān)進行光斑尺度評價的方案,通過matlab編程對該評價方案進行建模,證明了該方案的正確性,仿真分析了雙探測器距離、數(shù)據(jù)長度等因素對探測精度影響,探討了該方法對光斑尺度的探測極限及其可用性。
[Abstract]:It is of great value for the field of national defense, industrial processing and manufacturing to focus high power laser on long distance target and obtain high energy density light spot distribution. From the design of laser emission system to free space transmission of light field and feedback evaluation of laser focused spot, a large number of modeling, parameter selection and structural design are involved. The method of rational design and optimization of the system can save a lot of cost and time. Diffraction optics is one of the basic methods of modern optical engineering. The diffraction transmission can satisfy the simulation requirements of laser long distance focusing transmission. On the basis of the theory of laser diffraction transmission, this paper puts forward the modification of laser focusing simulation. In the algorithm, the mode of laser and the problem of partial coherence are discussed in detail. Combined with the specific design of the focusing system, the influence of various system parameters on the long distance focusing is analyzed and the experimental verification is carried out. In addition, a laser spotlight feedback evaluation method based on the echo speckle is proposed, which can improve the focus scale. Precision monitoring makes this article cover the simulation closed loop of laser emission, transmission and feedback evaluation to achieve a comprehensive analysis and evaluation of the performance of the system. The main work included in this paper are as follows: 1. on the basis of the scalar diffraction theory, the basic theory of laser beam transmission and the existing laser beam quality evaluation index, the different shapes are proposed. The simulation algorithm of laser beam transmission of state (initial field distribution, coherence of beam, transmission environment, etc.) is proposed. First, on the basis of Collins diffraction integral and linear frequency modulation Fourier transform (CFT), the application of wide window angle spectrum algorithm (WWAS).CFT can be used to make the input and output space domain. In separating the spatial frequency domain sampling, it does not increase the calculation burden of the algorithm when selecting the large computing window. It solves the problem of the rapid decline of the signal to noise ratio when the traditional angular spectrum method is used to simulate the long distance transmission of the laser. Moreover, the independence of the input and output space makes the algorithm sampling more flexible. Furthermore, the WWAS algorithm is sampled based on the signal to noise ratio analysis method. Under the condition of free space transmission, the transmission effect of wwas algorithm and other angular spectrum method is compared, and the advantages of the algorithm are given. Secondly, in order to simulate the transmission problem of multimode partially coherent laser beam, a linear equation group method based on the intensity distribution measurement for laser mode decomposition is proposed, and the method is used to use the method. Not only can the energy distribution of the coherent mode coefficient be obtained, but the correlation difference between different modes is obtained through the measurement of the finite longitudinal intensity distribution. The theory is verified by the method of constructing the beam in simulation. After the distribution of the laser mode, a simulation method of the partial coherent laser is proposed, and the FFT calculation is taken into account. The efficiency of the method also ensures the accuracy of the simulation of partially coherent beam transmission. Based on the beam transmission algorithm, the focusing characteristics of the laser long distance focusing system are analyzed. First, the laser distance focusing system is designed by using ZEMAX software, and the geometry parameters, laser parameters, focal shift and focus curve of the system are calculated. The beam propagation algorithm is used to analyze the variation of the diffraction loss and the distribution of the energy density of the focused spot caused by the aperture truncation of the system. The evaluation method of the generalized M2 factor is compared with the generalized M2 factor evaluation method, and the evaluation of the generalized factor in the aperture diffraction focusing system is given. On the basis of the theory, the method of joint simulation of ZEMAX and MATLAB is put forward. ZEMAX provides pupil aberration for the beam transmission algorithm. The distribution of focused spot is obtained by simulation calculation. It can analyze the rationality of tolerance distribution and give a reasonable compensation scheme. Then, the experimental method is used to measure the energy distribution of the focusing spot and the shape of the spot, and the imitation is verified. In addition, the effect of atmospheric turbulence on laser beam transmission is theoretically analyzed, and the change of M2 factor after the atmospheric disturbance is studied. The trade-off relationship between laser beam quality and atmospheric disturbance in the non adaptive system is given..3. studies the laser based on the statistical characteristics of the target echo speckle. Focused spot scale monitoring and feedback technology. For static or slow moving targets, two speckle evaluation factors are proposed to evaluate the laser focused spot scale. The two value Speckle Autocorrelation evaluation factor (CSAM) is calculated by the autocorrelation function of speckle, and increases with the decrease of the spot size; the two value speckle edge integration (csei) evaluation is the cause. The image of the echo speckle is two value and edge extraction, and the csei factor decreases with the reduction of the focus spot size. This paper simulates the influence of the parameters of the receiving system, the degree of target roughness and the length of the finite data on the accuracy of the two evaluation factors. The results of the theoretical analysis are verified by the experiment, and the two evaluation factors are proved. For the evaluation of the focus spot, a scheme to evaluate the spot scale using the correlation of dual detector signal is proposed for the fast moving target. The evaluation scheme is modeled by MATLAB programming, and the correctness of the scheme is proved. The influence of the distance of the dual detector and the length of the data on the detection accuracy is simulated and analyzed, and the results are discussed. Methods the detection limit and availability of spot scale are discussed.
【學位授予單位】：中國科學院研究生院(長春光學精密機械與物理研究所)
【學位級別】：博士
【學位授予年份】：2016
【分類號】：TN24
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本文編號：1916954