高精度相位差波前探测器的数值仿真和实验研究

相位差(PD)波前探测器具有光路简单、共光路测量等优点,不仅适合点目标,而且适合扩展目标.随着算法和硬件水平的不断提高,相位差法已经成为波前探测技术的一个重要发展方向.对相位差波前探测器进行了研究,成功实现了对点目标和扩展目标的波前探测,给出了数值仿真结果.针对点目标,搭建实验光路,对静态的单阶Zernike像差和随机...     

利用相位差异技术校准非共光路静态像差

提出了一种用相位差异(PD)技术对自适应光学(AO)系统的非共光路静态像差进行校准的方法。相位差异技术通过采集焦面和离焦面的单帧或多帧短曝光图像来估算波前相位畸变,同时对目标图像进行恢复。在闭环工作条件下,自适应光学系统利用相位差异算法在线检测成像光路的静态像差,并将得到的像差系数转化为变形镜的初始化面形,从而补偿非共光路的静态像差。实验结果表明,校准后的成像质量显著提高,目标半峰全宽降低了约14%,系统残差降低了约72%。成像光路在线检测得到的系统残差与闭环回路实测残差的水平趋于一致,证实了相位差异技术应用于光学检测的能力。该方法具有在无需改变原有自适应光路以及高信噪比条件下便可精确解算系统像差的优点,是大口径光电成像系统较为理想的光学检测技术之一。     

双波前校正器全光路像差校正自适应光学系统像差解耦分析

分析了双波前校正器全光路像差校正自适应光学系统的工作原理,并通过共模波前传感器中的两套波前传感器探测得到的波前信息进行数据差分融合,按照优化理论推导了两套波前校正器需要校正的像差公式.根据此像差公式,仿真分析了以两套61单元变形反射镜组成的双波前校正器全光路像差校正自适应光学系统的校正能力,并与单套波前校正器全光路像差校正自适应光学系统的校正能力进行了比较,结果验证了推导的像差公式的正确性,也说明了两套波前校止器不仅可以解耦,而且其校正效果与理想行程单套波前校正器全光路像差校正自适应光学系统的校正效果相当.     

基于整形光路的低阶像差校正方法

为满足激光束对远处目标辐照强度的要求,减小热效应对输出光束性能的影响,提出了一种基于整形光路的高能激光低阶像差校正方法。该方法根据波前探测器测到的光束波前畸变,利用激光器整形光路固有的光学元件和调整机构,通过高精密电动平移台和快反镜的快速动作,动态调整各镜片的间距,实时校正激光束的低阶像差,使输出光束恢复至平行出射,从而显著减小激光束的热漂移和热畸变,有效避免了长时间出光时光束的持续发散,极大改善了输出光束性能。试验结果表明,该方法具有校正量大、控制方便、结构紧凑等优点,能够很好地改善激光器输出光束质量,显著提高激光束远场作用效果。     

一种基于全息术的光学系统闭环像差补偿方法

提出了一种基于21单元变形镜与全息波前传感器的全息自适应光学系统, 并对其像差校正能力进行了分析. 首先描述了全息波前传感器基本原理, 并在薄全息图近似下给出基于快速傅里叶变换算法的全息波前传感器数值模型; 然后基于21单元变形镜的数值模型, 分析了该变形镜的波前校正能力; 在此基础上, 数值模拟并实验验证了全息自适应光学系统对静态像差的闭环校正能力.     

无调制两面锥波前传感器的衍射理论分析和数值仿真

两面锥波前传感器(two-sided pyramid wavefront Sensor,TSPWFS)是一种高空间采样率和高光能利用率的波前传感器.为了深入研究它的波前复原原理,采用波动光学理论详细推导了无调制TSPWFS的衍射理论,给出了无调制TSPWFS波前复原时线性重构矩阵的解析解,并且通过数值仿真确定出最佳的光瞳像中心间距,并对静态像差的波前复原及闭环校正进行数值仿真.分析结果表明,无调制TSPWFS具有波前复原时不需要现场测量响应矩阵,可以校正系统像差,闭环校正结果稳定等优点,可以在实际自适应光学系统中进行波前探测. 关键词： 自适应光学 两面锥波前传感器 波前复原     

相位光栅型曲率传感器的波前校正算法

 针对相位光栅曲率传感器能够测量波前曲率在光瞳面上分布的特点,提出了一种采用整个空间分布的曲率信号来实现波前校正的算法。用曲率型变形镜影响函数的曲率信号在光瞳面上的分布来拟合待校正波前的曲率信号,采用最小二乘方法得到变形镜的控制电压,实现波前校正过程。数值模拟了一种41单元曲率型自适应光学系统采用该算法的波前校正过程。结果表明,对4至28阶Zernike像差体现了校正效果,对曲率为0的Zernike像差校正效果略好于曲率不为0的Zernike像差。与传统分区法的校正效果相比,整体法对Zernike像差的校正效果基本相当。整体法无需对光瞳面上的曲率信号进行与电极分布相同的分区,降低了对系统校准的要求。     

自由曲面镜片波前像差扩束-缩束拼接技术

为解决波前传感器检测自由曲面镜片时测量口径不匹配,在拼接检测方法中测量过程及数据处理较为繁琐等问题,提出了一种测量自由曲面镜片的方法.该方法在扩大单次测量光束直径后对自由曲面镜片波前像差进行检测,再由波前传感器接收缩小后的带有扩束测量区域波前信息的光束.设计光路测量得到4个直径扩大10倍后的子孔径波前像差,完成扩束子孔径的波前重构及拼接.为验证实验的可靠性,对测得的扩束子孔径进行波前重构后与哈特曼传感器生成的子孔径像差峰谷值进行比较,并观察扩束子孔径拼接波面的平整性.实验结果表明:该方法能有效增大小口径波前传感器的测量范围,提高检测效率,可以用于大口径镜片的波前像差检测上.     

神光II升级装置波前传输计算模型与验证

基于衍射理论和神光II升级激光装置的光路结构及光学元件波前像差,建立了激光装置光束波前像差传输计算模型,用以获取在实验中难以取得,但对激光系统设计和安全运行非常重要的变形镜校正面型、放大器动态波前像差、空间滤波器波前像差和焦斑形态等过程数据。利用该模型对激光装置常规运行时的静态传输、变形镜加压静态传输和大能量发射3种状态下的波前传输进行理论分析,计算结果与实验测量相一致,并在此基础上对变形镜未加压大能量发射波前传输进行计算。计算模型可用于指导相关器件的设计,优化激光运行控制模式,有利于提高激光装置输出波前质量。     

基于模型的无波前探测自适应光学系统

基于波前梯度的二阶矩和修正后的远场强度分布近似呈线性关系,设计了一种基于模型的无波前探测自适应光学系统快速闭环控制算法。使用61单元变形镜、CCD成像器件等建立了自适应光学系统仿真平台,并以不同湍流强度下的波前像差作为校正对象,分析了这种基于模型的无波前探测自适应光学系统的收敛速度、校正能力及对不同像差的适应性。结果表明,基于模型的无波前探测自适应光学系统在快速收敛的同时,能够获得接近波前校正器件的理想校正能力。N阶模式像差校正时,系统只需要进行N+1次远场光斑的测量。和现有的各种无波前探测自适应光学系统控制算法相比较,基于模型的无波前探测自适应光学系统所需的测量次数大大减少。     

Eigenfunctions of Laplacian for phase estimation from wavefront gradient or curvature sensing

Modal cross coupling usually exists in wavefront estimation through Zernike polynomials. In order to cope with the problem, the eigenfunctions of Laplacian with Neumann boundary condition are proposed instead of Zernike polynomials to reconstruct phase from wavefront gradient or curvature sensing. It is proved theoretically that these modals can avoid modal cross coupling in both wavefront gradient sensing and curvature sensing. In wavefront gradient sensing, the coefficients of eigenfunctions of Laplacian can be obtained from the integral of the scalar product between the gradient of Laplacian's eigenfunctions and wavefront gradient signal. In wavefront curvature sensing, the coefficients of eigenfunctions of Laplacian can be calculated from the integral of the product of Laplacian's eigenfunctions and wavefront curvature signal. This approach is applicable on arbitrary apertures as long as eigenfunctions of Laplacian on apertures of arbitrary shape can be obtained.     

Determination of wavefront aberrations using a Fabry-Perot cavity

A new method for detecting wavefront aberrations using a Fabry-Perot cavity is described. A Fabry-Perot cavity transmits the cavity eigenmode which satisfies a resonance condition, while the other modes are reflected from the cavity. Utilizing this mode discrimination property, we can extract aberration components from incident aberrated light as reflected light from the cavity. Under the condition of a weak aberration, the amplitude profile of the reflected light can be approximated to the wavefront aberration. We can therefore determine the wavefront aberrations in a visualized form with the technique. We present the detection scheme and the first experimental verification of the technique. The detected aberration using this technique was in good agreement with the result on the basis of a conventional wavefront sensor.     

Effect of transition zone on wavefront aberration with treatment decentration after conventional refractive surgery

Based on the ablation profile of conventional refractive surgery, the influence of transition zone on induced wavefront aberrations with decentration, as well as laser oblique incidence, was studied. The results indicated that transition zone played a significantly important role in the influence of decentration on the postoperative aberrations. The induced coma increased rapidly with the increase of lateral translation of the centre of ablation. Furthermore, the induced spherical aberration increased theoretically as the translation increase and the sign of spherical aberration was usually positive for myopic correction. And yet it changed from positive to negative for hyperopic correction. In addition, the induced spherical aberration was related with the corrected refraction. As an important goal for refractive surgery, the optimal postoperative visual performance may be smoothly achieved by minimizing treatment decentration and optimizing transition zone in refractive surgery.     

初至到时波前算法及在地震走时CT中的应用

基于惠更斯原理,给出了一个简练的初至到时算法,并应用于地震走时层析成像。结果表明,新方法计算效率较Dijkstra最短路径法高一个数量级。     

Wavefront sensor using the Talbot effect

A method for measuring optical wavefronts is proposed by properly sampling the light amplitude distribution with a two-dimensional periodic mask. At the Talbot planes, where a reference wavefront (spherical or plane) would originate replicas of the aperture, distortions of the resulting selfimages take place. These intensity patterns are detected and processed for obtaining the required wavefront information. The approach is illustrated with some experimental results.     

Wavefront reconstruction using iterative discrete Fourier transforms with Fried geometry

A new kind of wavefront reconstruction algorithm is proposed in this paper, which can estimate the wavefront from its orthogonal gradients at different sample points. We model the gradients measured by wavefront sensor with the Fried geometry. Iterative discrete Fourier transforms and the correspondent Fried inverse filter in spatial frequency domain are introduced. No special boundary control is required to process the boundary condition in this algorithm. The stimulation and the experimental results show that the new algorithm has strong capability to fit the wavefront and it is more available if the sample points are few.     

基于空间光调制器的波面重建优化方法研究

针对不同非球面面形的实时检测需求,研究了基于空间光调制器的标准波面重建技术.基于空间光调制器波面重建的原理设计了干涉测量系统,依据空间光调制器的自身特点选取修正离轴计算全息编码方式实现对标准球波面的编码.针对实验中空间光调制器作为全息再现介质引起重建波面质量下降问题,提出了错位叠加优化方案,并将这一过程进行了模拟实验.结果表明,基于错位叠加方法的重建波面均方差值提高了近4.45倍.研究成果为非球面检测过程中标准波面的获取提供了可靠的理论基础.     

扩大人眼波前像差仪测量范围方法的研究

提出了一种扩大人眼波前像差仪测量范围的方法,该法综合了波前重建展开算法和波前探测的模板技术,大幅度扩大了波前测量范围.在待测波前像差超出展开算法测量范围的情况下,此方法仍能对像差正常测量.与模板技术相比,该法大幅扩大了可测的曲率范围.以球面波前入射的实验数据表明,所提出的新方法所能测量的最小曲率半径由模板法的75 mm降低到10 mm,并且由于本方法突破了展开算法的极限,实际上对局部曲率更高的波前仍可测量.     

基于Zernike多项式的波前传感器的光子受限的研究

应用基于Zernike多项式的波前探测和重构方法2,利用蒙特卡罗法,可求出探测器在不同的光子数下,其探测精度的变化。文章还给出了由不同的探测器组成的传感器,探测星等的变化情况。     

Analysis of the common characteristics of the Hartmann,Ronchi, and Shack–Hartmann tests

An overview of the settings of the planes for the filters and observed patterns in the Hartmann and Ronchi tests is presented. Also a new set of filters for both test were developed. In a similar way, it is easy to extend this analysis to the Shack–Hartmann test, and to propose a new Null Shack–Hartmann filter.