基于衍射光栅曲率波前传感器的实时波前重构研究

自适应光学系统要求波前传感器能实现动态实时测量,曲率波前传感技术符合这一发展要求。一种新型的基于扭曲衍射光栅的曲率波前传感器在探测装置的实现方法方面具有较大优势,其波前重构已应用于光学度量。根据衍射光学理论,对其探测信号进行数值模拟,并利用Neumann边界条件的Green函数法对其波前重构进行数值模拟。结果表明：Green函数法归结为2矩阵相乘,计算速度快,达到实时重构要求; Green函数法对阶数不高的Zernike多项式重构效果较好;影响重构误差的主要因素是光强梯度的边界噪声。     

微型自适应光学系统的波前重构算法

基于测量所得的 37通道微型机械薄膜变形镜的影响函数矩阵和微型自适应光学系统 ,给出模式法波前重构与补偿的微型变形镜的控制电压 ,模拟计算和微型自适应光学系统的实验结果说明所得结果是正确可行的     

基于模型选择的模式波前重构算法研究

基于Zernike模式的波前重构算法通常忽略实际波前像差构成的差异, 而用一定数量的低阶Zernike模式进行波前重构, 导致模式混淆或耦合等问题, 进而影响波前重构的精度. 根据信息论中的最小描述长度准则对重构模型的阶数进行了选择, 在此基础上应用非线性优化算法计算重构系数, 并最终实现波前重构; 对不同信噪比条件下振幅均匀分布入射光束的波前进行了重构. 结果表明: 该算法不但能够实现相对于现有算法相对较高的波前重构精度, 并且具有优良的噪声适应性, 体现了模型选择在模式法波前重构算法中的意义.     

基于循环式径向剪切干涉法的波前重建算法研究

提出一种基于循环式径向剪切干涉的波前重建算法。先将畸变波前经径向剪切干涉仪形成的空间相位调制干涉条纹图通过傅立叶变换处理获得对应的位相差分布,再直接采用迭代算法能精确重建原始波前,为ICF系统中复杂畸变波前的在线准确检测提供了可能,并给出了应用实例。     

哈特曼传感器对湍流畸变波前的泽尼克模式复原误差

分析了应用哈特曼传感器测量大气湍流畸变波前时,哈特曼传感器的泽尼克模式复原误差与子孔径划分形式、泽尼克模式复原阶数等的关系,给出了科尔莫哥洛夫湍流下计算哈特曼传感器模式复原误差的公式。对比分析了8×8子孔径划分和32×32子孔径划分的两个哈特曼传感器在实际大气湍流中同步测量的实验结果。     

基于循环式径向剪切干涉法的波前重建算法研究

 提出一种基于循环式径向剪切干涉的波前重建算法。先将畸变波前经径向剪切干涉仪形成的空间相位调制干涉条纹图通过傅立叶变换处理获得对应的位相差分布，再直接采用迭代算法能精确重建原始波前，为ICF系统中复杂畸变波前的在线准确检测提供了可能，并给出了应用实例。     

波荡器位相误差对自由电子激光

对波荡器位相误差对自由电子激光小信号增益的影响进行了分析讨论。对低增益情况解析地给出了波荡器位相误差引起的增益降低因子。结果表明:与自发辐射类似增益的降低与位相误差的方差成简单的指数关系，位相误差的线性变化部分引起最大增益的位移，还表明波荡器位相误差存在时Madey定理仍然成立。对高增益情况也给出了波荡器位相误差引起的增益降低因子。     

Large-aperture collimated wavefront evaluation based on sparse subaperture北大核心CSCD

A wavefront evaluation method based on sparse subaperture was proposed for the collimated wavefront of 300 mm aperture wavelength-tuned interferometer. The method used the wavefront data of sparse aperture to construct a uniform and equally spaced subaperture arrangement model and utilized the simultaneous fitting algorithm to realize the reconstruction of the full-aperture collimated wavefront. The change rules of subaperture spacing and subaperture size on the reconstruction accuracy were analyzed by the numerical calculation, and the optimized subaperture arrangement way was obtained. Finally, an optimized subaperture arrangement with a subaperture size of 10.8 mm and an adjacent subaperture center spacing of 9.72 mm was used for the sparse subaperture evaluation of 300 mm aperture collimated wavefront. The simulation results show that the optimized sparse subaperture evaluation wavefront residual peak valley (PV) value is 0.001 6λ and the residual root mean square (RMS) value is 1.689 3e−4 λ. Copyright ©2022 Journal of Applied Optics. All rights reserved.     

强激光畸变波前的高精度重构

高精度的波前重构,是实现对强激光波前畸变进行有效补偿与控制,提高光束质量的重要前提。先利用三个较远的衍射面及输入面上的强度信息,重构出强激光波前的以均方根梯度来描述的低频成分;再利用两个较近的衍射面及输入面上的强度信息,重构出强激光波前的以随机分布描述的中高频成分。当波前畸变的低频幅度小于或等于2λ,中高频幅度小于或等于0.15λ时,算法具有良好的收敛性能。     

小波变换在区域波前重构算法中的应用

在自适应光学中使用区域法进行波前重构的一个主要困难是计算量非常大。通过对重构矩阵进行小波变换 ,并对生成的矩阵选取门限 ,获得稀疏矩阵 ,从而可在对重构精度仅有轻微影响的情况下 ,显著降低计算量 ,提高计算速度。文中根据 Bowman[1 ]的理论分析 ,证实了小波变换应用于 Kolmogorov大气扰动重构的适用性 ,提出了适合工程设计应用的门限选择方法和评价参数 ,针对 Kovlmogorov大气扰动进行了计算机仿真 ,给出了有实际应用价值的结果     

环扇形分块主镜的波面拟合及重构方法研究

用有限元分析获得了环扇形分块主镜的镜面热变形数据,分别用圆域Zernike多项式和环扇域Zernike多项式对其进行了波面拟合,比较了用两种多项式的拟合精度。基于哈特曼-夏克波前传感器对由环扇形镜面热变形引起的畸变波前进行了模式法重构,分析了用上述两种多项式重构时矩阵条件数和测量误差对重构精度的影响。     

Making an optical vortex and its copies using a single spatial light modulator

We demonstrate a technique for making copies of optical vortices with the same topological charge using a single spatial light modulator. It has been shown that by using suitable diffractive optical elements, several copies of optical vortices with the same topological charge could be created. We have devised diffractive optical elements using a single spatial light modulator which could be used to make a vortex and its copies without inverting the charge. The nature of the topological charge was investigated with the interferometric technique. The experimental results are verified with the theoretical analysis. We anticipate that our results may find applications ranging from optical manipulation to quantum information.     

强激光畸变波前的高精度重构

 高精度的波前重构，是实现对强激光波前畸变进行有效补偿与控制，提高光束质量的重要前提。先利用三个较远的衍射面及输入面上的强度信息，重构出强激光波前的以均方根梯度来描述的低频成分；再利用两个较近的衍射面及输入面上的强度信息，重构出强激光波前的以随机分布描述的中高频成分。当波前畸变的低频幅度小于或等于2λ，中高频幅度小于或等于0.15λ时，算法具有良好的收敛性能。     

Wavefront reconstruction algorithm for wavefront sensing based on binary aberration modes

We propose a new algorithm for wavefront sensing based on binary intensity modulation. The algorithm is based on the fact that a wavefront can be expended with a series of orthogonal and binary functions, the Walsh series. We use a spatial light modulator(SLM) to produce different binary-intensity-modulation patterns which are the simple linear transformation of the Walsh series. The optical fields under different binary-intensity-modulation patterns are detected with a photodiode.The relationships between the incident wavefront modulated with the patterns and their optical fields are built to determinate the coefficients of the Walsh series. More detailed and strict relationship equations are established with the algorithm by adding new modulation patterns according to the properties of the Walsh functions. An exact value can be acquired by solving the equations. Finally, with the help of phase unwrapping and smoothing, the wavefront can be reconstructed. The advantage of the algorithm is providing an analytical solution for the coefficients of the Walsh series to reconstruct the wavefront. The simulation experiments are presented and the effectiveness of the algorithm is demonstrated.     

High-contrast imaging based on wavefront shaping to improve low signal-to-noise ratio photoacoustic signals using superpixel method

Photoacoustic(PA) imaging has drawn tremendous research interest for various applications in biomedicine and experienced exponential growth over the past decade. Since the scattering effect of biological tissue on ultrasound is two-to three-orders magnitude weaker than that of light, photoacoustic imaging can effectively improve the imaging depth.However, as the depth of imaging further increases, the incident light is seriously affected by scattering that the generated photoacoustic signal is very weak and the signal-to-noise ratio(SNR) is quite low. Low SNR signals can reduce imaging quality and even cause imaging failure. In this paper, we proposed a new wavefront shaping and imaging method of low SNR photoacoustic signal using digital micromirror device(DMD) based superpixel method. We combined the superpixel method with DMD to modulate the phase and amplitude of the incident light, and the genetic algorithm(GA) was used as the wavefront shaping algorithm. The enhancement of the photoacoustic signal reached 10.46. Then we performed scanning imaging by moving the absorber with the translation stage. A clear image with contrast of 8.57 was obtained while imaging with original photoacoustic signals could not be achieved. The proposed method opens new perspectives for imaging with weak photoacoustic signals.     

基于矢量波像差理论的两反光学系统装调研究

 为了实现对两反光学系统的精密装调,提出一种基于矢量波像差理论和波像差检测技术对失调量精确求解的装调方法。使用矢量波像差理论,将已设计的两反光学系统参数、失调量和失调光学系统的波像差之间建立方程;然后通过干涉测量法得到某一个视场的干涉图,利用条纹分析软件得到表征失调系统三阶彗差和三阶像散的泽尼克项系数,将泽尼克项系数代入方程从而求解出失调量。运用此方法对4 m口径RITCHEY-CHR-TIEN结构的天文望远镜进行模拟装调,最终求解的失调量与引入的失调量结果相互吻合,说明该装调方法正确。     

二次非球面镜检测中基于波前等高线图的调整方法

为了提高非球面光学元件的检测精度及效率,缩短调整环节的时间,分析了非球面干涉检测过程中被检非球面镜的调整误差对检测结果波前信息的影响,提出利用波前等高线图走势准确判断调整方向的调整方法。建立调整方向与被检镜失调量之间的关系,并利用光学设计软件Zemax仿真模拟检测光路,结合二次非球面镜的光学公差分析判断调整量的大小。基于该调整方法,利用Zygo激光干涉仪对口径为50 mm的双曲面进行检测,最终检测结果是RMS为0.014 ,实验表明该方法简单、可行。     

基于多对流速度的波前重构算法研究

在气动光学研究中,Ronald J. Hugo 和Eric J. Jumper的小孔径光束技术(SABT)波前重构算法在理论推导中忽略了与涡结构尺度相关的对流速度的差异,因此必然会给波前重构带来误差。用小波分析提取了上、下游探测光束输出的不同尺度的光程信号,通过计算两个探测光束输出的同一尺度信号的互相关系数,并利用互相关系数达到最大值对应的延迟时间研究了尺度相关的对流速度,然后再进行尺度相关的小孔径光束波前重构。结果表明：相对于单一对流速度的小孔径光束波前重构算法,该尺度相关的波前重构算法能有效地提高波前重构的精度。     

利用相关分析法测量空间光调制器的相位调制特性

基于一维干涉条纹图像的相关分析法可实现液晶空间光调制器相位调制特性的测试。给出了XGA2L11型电寻址液晶空间光调制器的相位现场测试原理、测试装置和测试步骤。利用范德卢格特型光电混合相关器对测试结果进行了实验验证。结果表明,该方法具有原理简单、适应性强和精度高等优点。     

直接液体冷却薄片激光器中抽运光均匀性对光束波前畸变的影响

近年来,直接液体冷却薄片激光器因其体积功率比小,热管理能力强等优势而成为研究热点.本文建立了一套直接液体冷却薄片激光器波前畸变的分析方法.应用该方法研究了直接液体冷却薄片激光器中抽运光均匀性对光束波前畸变的影响.计算分析了均匀性为92%, 80%和70%,且总的抽运功率不变时,激光器高阶像差分布情况.随着均匀性逐渐减弱,激光器中高阶像差逐渐增强,低阶像差量基本保持不变.实验中,设计加入波导和未加入波导结构,构建了均匀性为92%和70%的抽运光分布,分别测量了两种情况下的波前抖动情况以及波前畸变分布,抽运功率为5 k W时,测量获得了整个增益模块的光程差高阶分量(OPD_H),其畸变量均方根(RMS)值为0.66μm和0.79μm,实验结果和理论分析结果基本趋势一致.