基于自適應光學的激光束整形系統(tǒng)研究
發(fā)布時間：2018-12-29 10:30
【摘要】：由于自身良好的特性,激光自發(fā)明以來就得到廣泛的應用。但是隨著科學技術的發(fā)展,高斯光束已不能滿足實際應用中對光束形態(tài)與能量分布的要求。激光束整形技術應運而生。利用該技術對高斯光束進行整形,以獲取滿足應用要求的激光束。在眾多激光束整形技術中,基于自適應光學的激光束整形技術最具潛力和發(fā)展前景。它通過控制變形鏡面形調(diào)制入射光場復振幅分布,以實現(xiàn)光束整形,因而具有控制靈活、適應性好、面形多樣化、光能傳輸效率高、損傷閾值高等特點。但是,現(xiàn)有研究缺乏激光束整形系統(tǒng)的系統(tǒng)分析以及變形鏡參數(shù)對系統(tǒng)性能影響的研究。為了充分了解并發(fā)揮基于自適應光學的激光束整形系統(tǒng)的性能,本文對其進行了一系列深入詳細的分析研究。第一,為了對激光束整形系統(tǒng)性能進行量化分析,本文建立了基于近場調(diào)制位相與遠場整形光強的系統(tǒng)性能評價指標體系,包括近場調(diào)制位相的PV與RMS值,遠場整形光強的相關系數(shù)與光強偏離殘差平方和均值。第二,近場調(diào)制位相是激光束整形系統(tǒng)研究的重要對象。由于方形或圓形均勻目標光強自身的數(shù)學特性,近場調(diào)制位相近似解可通過積分漸近近似方法獲取。為了解決積分漸近近似法的局限性,本文提出一種基于澤尼克模式的隨機并行梯度下降算法以獲取近場調(diào)制位相。第三,目標光強形態(tài)大小是激光束整形系統(tǒng)的一個重要參數(shù),不僅對近場調(diào)制位相分布有著直接影響,也會影響遠場整形光強。本文利用拉格朗日乘數(shù)法等數(shù)學方法,分析目標光強形態(tài)大小對近場調(diào)制位相及遠場整形光強的影響。第四,光瞳截斷作用直接影響入射光場及近場調(diào)制位相分布,并間接影響遠場光強整形性能。在研究光瞳截斷作用對遠場光強整形性能影響規(guī)律的基礎上,本文建立遠場光強整形性能評價指標關于光瞳半徑及目標光強形態(tài)大小參數(shù)的數(shù)學模型。根據(jù)數(shù)學模型,本文提出一種最優(yōu)光瞳半徑的選取方法。第五,變形鏡是基于自適應光學的激光束整形系統(tǒng)的核心位相調(diào)制元件。變形鏡面形由驅(qū)動器影響函數(shù)及控制電壓決定。本文研究了變形鏡影響函數(shù)數(shù)學模型中的參數(shù):驅(qū)動器間距、交連值及高斯指數(shù),對激光束整形系統(tǒng)性能的影響。其中的變化規(guī)律,為變形鏡參數(shù)選擇提供依據(jù)。第六,激光束整形系統(tǒng)研究目標是獲取與目標光強盡可能相似的遠場整形光強。變形鏡擬合近場調(diào)制位相常用方法是最小二乘法,可以獲取最小擬合誤差。本文分析了最小擬合誤差與最優(yōu)遠場整形性能的關系,發(fā)現(xiàn)最小擬合誤差并不對應最優(yōu)遠場整形性能。在此基礎上,本文提出了一種基于最小二乘法的隨機并行梯度下降優(yōu)化算法,并利用該方法進行近場調(diào)制位相擬合,激光束整形系統(tǒng)性能有明顯提升。第七,本文研究近場調(diào)制位相分布特性,并據(jù)此選擇變形鏡,搭建基于Bimorph的無波前探測激光束整形系統(tǒng),利用隨機并行梯度下降控制算法完成方形均勻目標光強整形實驗。第八,為彌補單變形鏡激光束整形系統(tǒng)的不足,本文利用Bimorph變形鏡、3mm極間距PZT變形鏡以及夏克-哈特曼波前探測器,搭建基于雙變形鏡的激光束整形系統(tǒng)。利用直接斜率法閉環(huán)實現(xiàn)遠場方形與圓形均勻目標光強整形實驗。為了驗證變形鏡擬合方法對遠場整形性能影響,利用直接斜率法獲取的控制電壓為初始值,通過雙擾動隨機并行梯度下降算法繼續(xù)優(yōu)化電壓。對比發(fā)現(xiàn),隨機并行梯度下降算法優(yōu)化電壓有利于遠場光強整形性能提升。
[Abstract]:Due to its good characteristics, the laser has been widely used since the invention. However, with the development of science and technology, the Gaussian beam has not been able to meet the requirement of the beam form and energy distribution in the practical application. Laser beam shaping technology has come into being. The Gaussian beam is shaped by the technique to obtain a laser beam that meets the application requirements. In many laser beam shaping techniques, the laser beam shaping technology based on the adaptive optics is the most promising and promising. The invention has the characteristics of flexible control, good adaptability, diversified surface shape, high light energy transmission efficiency, high damage threshold and the like by controlling the complex amplitude distribution of the incident light field by controlling the deformation mirror-shaped modulation. However, the present study lacks the systematic analysis of the laser beam shaping system and the study of the effect of the deformation mirror parameters on the performance of the system. In order to fully understand and give full play to the performance of the laser beam shaping system based on adaptive optics, a series of in-depth and detailed analysis of the laser beam shaping system is carried out. First, in order to carry out the quantitative analysis of the laser beam shaping system performance, the system performance evaluation index system based on the near field modulation bit phase and the far field shaping light intensity is established, including the PV and RMS values of the near field modulation bit phase, The correlation coefficient of the far field shaping light intensity and the light intensity deviate from the mean square of the residual sum of the residual. Second, the near field modulated phase is an important object of the laser beam shaping system. The approximate solution of the near field modulation bit can be obtained by the integral asymptotic approximation method due to the mathematical characteristics of the square or circular uniform target light intensity. In order to solve the limitation of the integral asymptotic approximation method, a random parallel gradient descent algorithm based on Zernike mode is proposed to obtain the near field modulation bit phase. Thirdly, the size of the target light intensity is an important parameter of the laser beam shaping system, which not only has a direct influence on the distribution of the near field modulation bit, but also affects the light intensity of the far field. In this paper, by using the Lagrange multiplier method and other mathematical methods, the influence of the size of the target light intensity on the light intensity of the near field modulated phase and the far field is analyzed. Fourth, the optical pupil truncation effect directly affects the distribution of the incident light field and the near field modulation bit, and indirectly influences the light intensity shaping performance of the far field. On the basis of the study of the influence of the optical pupil truncation on the light intensity shaping performance of the far field, this paper sets up a mathematical model of the optical pupil radius and the parameter of the shape and size of the target light intensity. According to the mathematical model, this paper presents a method for selecting the optimal pupil radius. Fifth, the deformable mirror is a core bit phase modulation element based on the adaptive optics laser beam shaping system. The deformation mirror shape is determined by the driver influence function and the control voltage. In this paper, the parameters in the mathematical model of the influence function of the deformable mirror are studied: the driver spacing, the intersection value and the Gaussian index, and the effect on the performance of the laser beam shaping system. The rule of variation is to provide the basis for selecting the parameter of the deformable mirror. Sixth, the aim of the laser beam shaping system is to obtain a far field shaping light intensity that is as close as possible to the target light intensity. The common method of fitting the near field modulation bit by the deformable mirror is the least square method, and the minimum fitting error can be obtained. In this paper, the relation between the minimum fitting error and the optimal far field shaping performance is analyzed, and it is found that the minimum fitting error does not correspond to the optimal far field shaping performance. On this basis, a random parallel gradient descent optimization algorithm based on the least square method is proposed, and the near field modulation bit is fitted by the method, and the performance of the laser beam shaping system is obviously improved. Seventh, this paper studies the distribution characteristics of the near-field modulation bit, and then selects the deformable mirror, sets up a non-wave front-probe laser beam shaping system based on the Bimorph, and uses the random parallel gradient descent control algorithm to complete the square uniform target light intensity shaping experiment. In order to make up for the defects of the laser beam shaping system of the single-deformable mirror, the laser beam shaping system based on the double-deformable mirror is set up by using the Bimorph deformable mirror, the 3mm-pole pitch PZT deformable mirror and the summer-Hartmann wave front detector. The direct slope method is used to realize the light intensity shaping experiment of the far field square and the circular uniform target. In order to verify the influence of the fitting method of the deformation mirror on the shaping performance of the far field, the control voltage obtained by the direct slope method is the initial value, and the voltage is continuously optimized by the double-disturbance random parallel gradient descent algorithm. It is found that the optimized voltage of the random parallel gradient descent algorithm is favorable for the improvement of the light intensity shaping performance of the far field.
【學位授予單位】：中國科學院研究生院(光電技術研究所)
【學位級別】：博士
【學位授予年份】：2016
【分類號】：TN249
本文編號：2394725
[Abstract]:Due to its good characteristics, the laser has been widely used since the invention. However, with the development of science and technology, the Gaussian beam has not been able to meet the requirement of the beam form and energy distribution in the practical application. Laser beam shaping technology has come into being. The Gaussian beam is shaped by the technique to obtain a laser beam that meets the application requirements. In many laser beam shaping techniques, the laser beam shaping technology based on the adaptive optics is the most promising and promising. The invention has the characteristics of flexible control, good adaptability, diversified surface shape, high light energy transmission efficiency, high damage threshold and the like by controlling the complex amplitude distribution of the incident light field by controlling the deformation mirror-shaped modulation. However, the present study lacks the systematic analysis of the laser beam shaping system and the study of the effect of the deformation mirror parameters on the performance of the system. In order to fully understand and give full play to the performance of the laser beam shaping system based on adaptive optics, a series of in-depth and detailed analysis of the laser beam shaping system is carried out. First, in order to carry out the quantitative analysis of the laser beam shaping system performance, the system performance evaluation index system based on the near field modulation bit phase and the far field shaping light intensity is established, including the PV and RMS values of the near field modulation bit phase, The correlation coefficient of the far field shaping light intensity and the light intensity deviate from the mean square of the residual sum of the residual. Second, the near field modulated phase is an important object of the laser beam shaping system. The approximate solution of the near field modulation bit can be obtained by the integral asymptotic approximation method due to the mathematical characteristics of the square or circular uniform target light intensity. In order to solve the limitation of the integral asymptotic approximation method, a random parallel gradient descent algorithm based on Zernike mode is proposed to obtain the near field modulation bit phase. Thirdly, the size of the target light intensity is an important parameter of the laser beam shaping system, which not only has a direct influence on the distribution of the near field modulation bit, but also affects the light intensity of the far field. In this paper, by using the Lagrange multiplier method and other mathematical methods, the influence of the size of the target light intensity on the light intensity of the near field modulated phase and the far field is analyzed. Fourth, the optical pupil truncation effect directly affects the distribution of the incident light field and the near field modulation bit, and indirectly influences the light intensity shaping performance of the far field. On the basis of the study of the influence of the optical pupil truncation on the light intensity shaping performance of the far field, this paper sets up a mathematical model of the optical pupil radius and the parameter of the shape and size of the target light intensity. According to the mathematical model, this paper presents a method for selecting the optimal pupil radius. Fifth, the deformable mirror is a core bit phase modulation element based on the adaptive optics laser beam shaping system. The deformation mirror shape is determined by the driver influence function and the control voltage. In this paper, the parameters in the mathematical model of the influence function of the deformable mirror are studied: the driver spacing, the intersection value and the Gaussian index, and the effect on the performance of the laser beam shaping system. The rule of variation is to provide the basis for selecting the parameter of the deformable mirror. Sixth, the aim of the laser beam shaping system is to obtain a far field shaping light intensity that is as close as possible to the target light intensity. The common method of fitting the near field modulation bit by the deformable mirror is the least square method, and the minimum fitting error can be obtained. In this paper, the relation between the minimum fitting error and the optimal far field shaping performance is analyzed, and it is found that the minimum fitting error does not correspond to the optimal far field shaping performance. On this basis, a random parallel gradient descent optimization algorithm based on the least square method is proposed, and the near field modulation bit is fitted by the method, and the performance of the laser beam shaping system is obviously improved. Seventh, this paper studies the distribution characteristics of the near-field modulation bit, and then selects the deformable mirror, sets up a non-wave front-probe laser beam shaping system based on the Bimorph, and uses the random parallel gradient descent control algorithm to complete the square uniform target light intensity shaping experiment. In order to make up for the defects of the laser beam shaping system of the single-deformable mirror, the laser beam shaping system based on the double-deformable mirror is set up by using the Bimorph deformable mirror, the 3mm-pole pitch PZT deformable mirror and the summer-Hartmann wave front detector. The direct slope method is used to realize the light intensity shaping experiment of the far field square and the circular uniform target. In order to verify the influence of the fitting method of the deformation mirror on the shaping performance of the far field, the control voltage obtained by the direct slope method is the initial value, and the voltage is continuously optimized by the double-disturbance random parallel gradient descent algorithm. It is found that the optimized voltage of the random parallel gradient descent algorithm is favorable for the improvement of the light intensity shaping performance of the far field.
【學位授予單位】：中國科學院研究生院(光電技術研究所)
【學位級別】：博士
【學位授予年份】：2016
【分類號】：TN249
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