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。     

折轴三反射光学系统的计算机辅助装调技术研究

 给出计算机辅助装调中失调量与像差关系的数学模型,利用Zemax对折轴三反射光学系统进行失调仿真,得到失调数据,再对数据进行分析和处理,求得次镜和三镜的灵敏度矩阵,还对各种初级像差与各装调参量之间的对应关系及该系统的失调特性进行讨论。根据以上分析结果,最终确定了共轴三反射光学系统的装调方案。为了验证方案的可行性,在Zemax中对共轴三反射光学系统人为地加入不同的失调量后,按照确定的装调方案,利用建立的计算机辅助装调数学模型计算出失调量的大小和方向,再根据计算结果对共轴三反射光学系统进行调整,仿真结果和实际装调结果都证明该方案是可行的。     

光学系统辅助装调技术研究

光学系统装调技术是高功率激光工程中的关键支撑技术之一。对光学系统装调中影响系统光束质量的误差来源进行了分析,并根据像差的装调方式进行了分类。对这两类像差的辅助装调方式进行了比较和仿真模拟。针对第一类像差,在装调模型中代入失调系统检测得到干涉图,利用计算机辅助装调模型计算出失调量的大小和方向,确定出系统的装调方案。仿真结果显示,对系统调整工作有较好指导作用。针对第二类像差,利用元件加工面形之间波像差的互补性,优化调整光学元件的装校姿态。仿真结果显示,系统的光束质量口由预期的4．916优化为1．187,提高了多元件光学系统的光束质量。     

计算机辅助装调方法在离轴卡塞格林系统中的应用

针对高成像质量的离轴光学系统的计算机辅助装调问题,许多研究者提出了利用泽尼克系数建立灵敏度矩阵来求解失调量,但这种方法只有在泽尼克系数和失调量存在线性关系的前提下才能准确求解。提出了一种新的能求解较大失调量的计算机辅助装调方法,用此方法对一个口径为250mm的离轴卡塞格林系统进行了装调,得到了中心视场波像差RMS为0.0405λ(λ=632.8nm)。由这种方法计算出的失调量不仅准确,而且能够用于系统装调初期存在大失调量的情况。因此用这种方法能够显著提高离轴光学系统的装调效率。     

提高平行光管分划板装调精度新方法研究

推导了分划板失调量与待测系统调制传递函数(MTF)下降之间的解析表达式,对光管和待测系统焦距比与分划板装调精度之间的数学关系进行仿真分析,发现焦距比为1,分划板轴向装调误差为0.0012mm引起的待测系统MTF下降为0.01。据此提出依据Zernike系数定量指导装调,采用数字干涉仪与平行光管、分划板构成干涉光路进行逐次迭代调整的方法。实验与数学分析均表明,上述方法可显著提升分划板装调精度,其引起的探测器离焦导致的MTF下降可控制在0.013。实验结果与理论值之间的偏差表明,环境扰动等不确定度对标定精度产生影响,在测试环境良好的条件下采用上述装调方法,使用焦距与待测光电系统焦距相当的平行光管就可满足高精度光学标定与装调的测试需求。     

光学系统计算机辅助装调的坐标基准过渡方法

为实现光学系统计算机辅助装调工程化应用,达到根据失调量的计算值对光学元件进行空间位置误差校正的目的,提出了失调量的计算值和调整机构调整量之间的过渡方法,利用坐标变换和最小二乘优化算法建立了失调量-调整量的关系模型,完成了两者坐标基准过渡。仿真结果表明,根据此方法自编程序计算出的平移调整量精度可达10-6 mm量级,角度调整量精度可达0.02″量级,计算精度远高于光学系统的装调要求。在模拟装调过程中,与直接采用失调量计算值对元件调整的结果相比,此方法的调整结果明显好于前者。对于不同的光学元件装卡方式和调整机构,可对此算法的相关参量进行赋值,灵活运用于不同的工况,为计算机辅助装调的实际工程化应用提供理论依据。     

一种非稳腔计算机辅助装调方法的数值模拟

谐振腔的自动准直技术是高功率激光器工程实践中的关键技术之一.针对这一问题,对非稳腔的计算机辅助装调方法进行了研究,并对该过程进行了数值模拟.在失调参量和像差系数小范围内线性近似的前提下,获取到一系列表征系统失调的像差值之后,通过求解线性方程组来计算系统的失调量.根据求解结果对失调系统进行修正.数值模拟结果表明单结构参量失调可以很快求出,多结构参量失调情况通过几次迭代求解后也能得到比较理想的结果.目前已经可以确定多个同时存在的失调量(包含倾斜和偏心).倾斜量的求解范围约为10～104 μrad,偏心量的求解范围约为10-2～1 mm.这种辅助装调方法能够有效地指导谐振腔的精装调过程,为今后实际的激光器谐振腔系统的自动调节提供了一种方法.     

无焦压缩光路系统的计算机辅助装调方法

为了解决随机成分多、调节灵敏度高的离轴反射式系统的精确装调问题,介绍了干涉测量与计算机优化技术相结合的方法,建立了各元件失调量与初级像差之间的关系,以及元件间的像差相互补偿关系,通过干涉测量采集系统全视场的波前差,反向优化得到各元件的失调量,在波长为632.8 nm时,无焦压缩光路系统全视场平均出射波前优于RMS0.055 ,压缩比误差小于5,实现了无焦压缩光路系统高精度、高效率的装调。     

基于矢量波像差理论的两反系统装配失调解算方法

以矢量波像差理论中的三级像差理论为基础,提出了一种两反系统装配失调量解算方法。该方法仅采用轴上视场波前像差系数建立失调量解算模型,然后基于球差系数解算间隔误差,并基于彗差和像散系数解算偏心和倾斜误差,大幅提高了解算精度和效率。以某一两反光学系统为例,利用光学设计软件Zemax进行模拟装调,系统轴上视场失调像差系数均减小到10~(-7)数量级,失调误差均校正到10~(-5)数量级,达到了良好的装调效果。最后,利用该失调量解算模型指导两反光学系统的装调,失调量解算精度及装调精度达到了使用要求。Zemax模拟装调结果和实际装调效果均证明了所提方法的正确性。     

共轴三反光学系统卧式装调技术

共轴三反光学系统是空间光学遥感器常用的设计形式,以“高分一号”遥感卫星高分辨率相机装调为例,对共轴三反系统计算机辅助装调技术进行了研究。提出以主镜光轴为装调基准,通过调整三镜控制系统视场和调整次镜控制系统像差的装调方法,分析了次镜和三镜的失调量与Zernike系数变化关系,由光学设计软件求得系统灵敏度矩阵,用于指导系统装调工作,提高了装调精度,缩短了装调周期。测试结果表明:光学系统各视场Zernike系数优于0.05λ,系统波相差RMS值优于0.06λ,系统通过在轨成像测试,图像清晰,层次丰富。     

Moderating registration misalignment in voxelwise comparisons of DTI data: a performance evaluation of skeleton projection

An evaluative methodology and five accompanying performance measures were developed to quantitatively assess the performance of the skeleton projection algorithm constituting the heart of tract-based spatial statistics (TBSS). The performance measures were designed to quantify the accuracy of skeleton projection in its indented task of alleviating any residual misalignment that may remain after image registration. A ground truth fractional anisotropy (FA) image was slightly warped using a realistic warp field that served to model post-registration residual misalignment of varying magnitudes. Skeleton projection was then used to register the warped FA image to the ground truth. Performing skeleton projection was found to yield up to 50% better correspondence between the values of FA compared to smoothing, despite the fact that less than 10% of post-registration misalignment was corrected. The align-max-with-max strategy underlying TBSS was posited as a potential explanation for this high correspondence in the values of FA, at the expense of lesser alignment between anatomically concordant voxels.     

A simple method for automatic cavity alignment of a solid-state laser

Misalignment of a laser cavity would result in the displacement of beam location on the cavity mirrors. We present a simple method for automatic cavity alignment of a solid-state laser through detecting the location of the laser beam on the rear mirror, with which neither external alignment beams nor modifications to the cavity are required. The rear mirror of the laser cavity is replaced by a tip/tilt mirror to compensate for the misalignment. Experiments show that this method could effectively correct the misalignment of the laser cavity and restore the output power to almost the original value when the resonator is well aligned.     

A simple method for calculating coupling efficiency in optical interconnection system involving various misalignment parameters

A simple method is presented to approximate the coupling efficiency in optical interconnection systems, which are affected by alignment parameters of various optical elements. The method considers geometric effects of alignment parameters, not considering the material-dependent losses which are insensitive to the misalignment parameters. To indicate the independent contribution of a given alignment parameter, we define a partial coupling efficiency (PCE) that reflects the effect of only one parameter on a local coupling efficiency at an optical element. The total coupling efficiency (TCE) in the whole system is approximated by multiplications of the PCEs calculated for each parameter and normalization factors. For an interconnection scheme using a 45°-ended waveguide, we demonstrate by considering many misalignment parameters simultaneously that our approximation is well matched to the results of the simulated TCE.     

基于多视场星点椭圆率的望远镜主动准直方法

光学元件的准直失调会引起天文望远镜在观测过程中的像质退化,该问题在大口径快焦比的天文光学系统中更为突出。针对此问题,本文提出一种用于望远镜日常观测过程中的主动准直方法,通过星像解算实时校正副镜位置及姿态达到维持望远镜像质的目的。该方法基于多视场星点椭圆率,利用粒子群优化算法迭代求解望远镜光学元件失调量,从而校正由光学元件失调引起的低阶像差。利用1.6 m多通道测光巡天望远镜光学系统进行模拟仿真,求解副镜失调量残余误差小于1%,在系统设计公差范围以内。利用南极巡天望远镜AST3-3模拟及实验验证,表明该方法可高精度求解望远镜光学元件的失调误差。     

Dynamic time responses of a flexible spinning disk misaligned with the axis of rotation

Using the finite element method, this study investigates the dynamic time responses of a flexible spinning disk of which axis of rotation is misaligned with the axis of symmetry. The misalignment between the axes of symmetry and rotation is one of major vibration sources in optical disk drives such as CD-ROM, CD-R, CD-RW and DVD drives. Based upon the Kirchhoff plate theory and the von Karman strain theory, three coupled equations of motion for the misaligned disk are obtained: two of the equations are for the in-plane motion while the other is for the out-of-plane motion. After transforming these equations into two weak forms for the in-plane and out-of-plane motions, the weak forms are discretized by using newly defined annular sector finite elements. Applying the generalized-α time integration method to the discretized equations, the time responses and the displacement distributions are computed and then the effects of misalignment on the responses and the distributions are analyzed. The computation results show that the misalignment has an influence on the magnitudes of the in-plane displacements. It is also found that the misalignment results in the amplitude modulation or the beat phenomenon in the time responses of the out-of-plane displacement.     

In situ technique for measuring the orthogonality of a plane wave to a substrate

A new compact in situ method of measuring the perpendicularity of a plane wave to a substrate is proposed. Off-axis cylindrical Fresnel lenses are used to focus a portion of the incident plane wave onto target lines. The displacement of the focal line from the targets is determined by the degree of angular misalignment. The proposed design has been incorporated into a 10-mm-thick fused-silica module, which enables us to obtain an alignment precision of better than 0.0083 degrees. This method is designed for use in optical assembly procedures that require an incident collimated beam that is normal to the alignment features. Experimental results are presented.     

基于像差校正的望远系统装调方法研究

为了保证望远镜装配完成后的成像质量和其他关键指标,提出基于像差校正的望远镜装调方法。首先利用Zemax建立光学系统模型,模拟光学零件失调状态,分析各零件的每种失调状态对各类像差的影响情况,进而定量计算光学零件对系统像差的敏感矩阵,得出系统失调特性,拟定最佳装调方案。在此理论分析的指导下,进行基于星点检验法的装调实验,装调后仪器各项指标达到要求,分辨率优于技术指标要求7.5,验证了基于像差校正的光学系统装调方案的可行性。