基于Bayesian原理的低陡度光学镜面面形误差离子束修正驻留时间算法

离子束修形是一种高效修除镜面误差的技术,驻留时间求解算法是此技术的关键问题之一。以光学镜面计算机控制成型原理为基础,建立基于Bayesian原理的平面镜面驻留时间算法,对数据边缘进行Gaussian延拓以消除边缘效应。分析驻留时间近似速度实现方式的实现误差与工艺参数的关系,通过在算法中引入附加光滑修正因子以提高驻留时间实现精度。在适当的路径规划下,将低陡度非球面修形过程近似用平面修形过程线性模型来描述,最终形成低陡度光学镜面面形误差离子束修正中驻留时间的快速近似算法。利用此算法对 100平面镜和 200球面镜进行修形加工,加工收敛率均可达9。研究结果表明：线性化近似模型是合理的,速度近似计算是可行的,基于Bayesian原理的低陡度非球面驻留时间求解算法是一种快速高效面形控制技术,可对镜面进行确定性精确修形。     

小特征尺寸连续位相板离子束修形的误差分析

针对小特征尺寸连续位相板中频段成分分布广、误差梯度大的面形特点,分析了离子束修形技术加工连续位相板过程中影响加工精度的几种因素,包括扫描步距、材料去除方式、定位精度和材料去除量求解。分析指出:根据采样定理确定去除函数的扫描步距可实现对不同尺寸特征单元的有效加工;进一步优化材料去除方式能够确保修形过程中驻留时间的平稳运行,实现全频段误差一致收敛。另外,采用面形匹配方法对测量误差进行校正实验,可获取准确的面形材料去除量;而采用提高去除函数定位精度的方法可显著提升小尺寸特征单元的加工精度。基于研究结果,在消除各种工艺误差的基础上,采用离子束修形技术对特征尺寸小至1.5mm,面形峰谷值小于200nm,面形梯度高至1.8μm/cm的连续位相板进行了高精度加工,结果显示:加工面形与理论面形的匹配精度达到8.1nm(RMS),证实了误差分析的准确性。     

光学平面镜面离子束修形中速度模式的实现

针对光学平面镜面离子束修形工艺中,目前采用的位置加工模式额外加工时间长、精度不高的缺点,提出离子束修形工艺中的速度加工模式,并给出速度加工模式中如何根据驻留时间计算加工中进给速度的方法。使用速度模式在自研的离子束加工机床KDIFS-500上进行了验证试验,对一块直径98 mm的微晶玻璃平面样镜进行修形,加工时间为17.5 min,样镜经过一次加工后,其面形误差的方均根值由初始的33.2 nm提高到了3.1 nm,面形收敛比高达10.7。试验结果表明,速度模式加工比位置模式加工可以缩短加工时间,提高加工精度,获得更大的面形收敛比。     

束流参数对光学镜面离子束加工去除函数的影响分析

在离子束光学镜面修形加工中,束函数的形状和大小决定了加工的修形能力和加工效率.虽然束函数的形状和大小可以通过一组工艺参数进行调节,然而,这组工艺参数对束函数影响的理论计算较为复杂,而且理论计算值与实验值也吻合的通常存在差异.为了找出工艺参数对束函数的影响规律,本文通过实验研究了离子束的几个主要的工艺参数(屏栅电压、屏栅电流、加速栅电压、中和极功率、氩气流量)对束函数的影响规律,建立了光学镜面离子束加工基本工艺参数数据库,为光学镜而离子束修形加工的工艺参数选择提供了指导依据.     

离子束抛光高陡度离轴非球面的去除函数修正

研究了三轴离子束系统抛光大口径高陡度离轴非球面过程中镜面曲率变化对离子束抛光去除函数的影响。提出了利用修正矩阵修正各驻留点处的去除函数信息,进而实现对高陡度离轴非球面高精度抛光的方法。该方法通过对离轴非球面进行坐标转换来降低陡度变化对去除函数的影响;基于Sigmund溅射理论分析离子束抛光非球面材料的去除率,建立离子束抛光非球面去除函数模型,计算了材料去除率在非球面各驻留点处的变化。最后,根据投影原理计算在各驻留点处去除函数的半宽,得到以驻留点矩阵为基础的去除函数修正矩阵,从而掌握每一个驻留点处的去除函数信息,然后根据计算机控制光学表面成形(CCOS)原理解得加工驻留时间分布。选取口径为900mm×680mm,离轴量为350mm的离轴体育场型非球面镜进行了抛光实验,实验显示抛光后非球面镜面形精度的RMS值由32.041nm达到11.566nm,收敛率达2.77,对实际加工具有指导意义。     

光学非球面离子束加工模型及误差控制

摘要：通过对离子束加工系统的分析,给出了加工非球面光学元件的离子源子系统运动模型公式,并将驻留时间求解的反卷积过程转化为求解线性矩阵方程模型,便于进一步优化求解;对加工过程中不可避免的离子源定位误差过程进行了分析,指出其对最终面形精度的影响可归结为一个系数因子的控制上,并提出了综合考虑离子束材料去除函数和定位误差的方法来控制系数因子,降低对定位系统的苛刻精度要求,保证过程稳定的同时降低设备成本。     

基于线性代数和正则化方法的驻留时间算法

将加工的数学模型由去除函数与驻留时间的卷积过程转变为去除矩阵与驻留时间向量的乘积过程,从而将驻留时间的计算变为线性方程的求解。因测量误差而引入的噪声导致了方程的病态,传统的数值计算方法失效,因此,用Tikhonov正则化对建立的模型进行求解。采用了无须任何先验知识的自适应方法选取正则化参数。对同一组数据采用其他的驻留时间算法进行计算并对比,精度提高了30％以上。最后对一组面形数据使用实际参数进行了模拟加工,加工后的PV、RMS的收敛比率分别达到0.48,0.62,满足实际驻留时间的求解要求。该方法稳定收敛,精度高,设置灵活,是一种较实用的驻留时间算法。     

用神经网络求实时控制的电化学齿轮修形过程的施电规律

提出了一种基于实时控制的电化学齿轮修形的新方法 ,设计并制作了电化学齿轮修形的加工装置 ,建立了修形齿面去除规律的数学模型。利用人工神经网络的方法在已知修形量及修形区域的情况下求取了加工施电规律 ,应用满足加工条件的试验数据对网络进行了学习训练 ,使网络映射成功 ,以此为基础 ,根据要求修形量及修形特点 ,反求取实时控制的电化学修形的施电规律。通过着色试验和所测得的齿形齿向曲线 ,证明了该修形工艺方法的可行性 ,在实际生产中有较大的应用与推广价值。     

计入轴线偏差的斜齿轮副齿面磨损分析

针对齿轮轴线偏差会加剧齿面磨损的问题,提出了一种综合了数值仿真和有限元的方法,对齿面磨损进行了仿真分析。以单对斜齿轮副为研究对象,基于Archard磨损公式,建立了计入轴线偏差的齿面磨损深度解析模型;在此基础上,分析了轮齿螺旋角修形、渐开线鼓形修形对齿面最大磨损深度的影响,并据此制定了减缓齿面磨损的轮齿综合修形策略。研究结果表明:同一工况下,斜齿轮垂直平面轴线偏差比水平轴线偏差对齿面磨损的影响更为显著;采用渐开线鼓形修形与螺旋角修形的综合修形方式可降低齿轮轴线偏差对齿面磨损的影响;该研究结果可为减缓齿面磨损过程制定出合适的修形策略。     

圆弧刀廓加工螺旋锥齿轮的全齿面分区修形

针对圆弧刀廓加工螺旋锥齿轮副,以提高啮合传动平稳性为目标,研究了螺旋锥齿轮全齿面分区修形的方法。首先推导了圆弧刀廓双重螺旋法加工的小轮齿面方程,将圆弧刀廓修形和主动设计方法相结合,将螺旋锥齿轮齿面划分为5个修形区域,实现了对小轮全齿面的预控设计,得到了高重合度、低传动误差的目标齿面;并运用有限元技术对比分析了优化前后的齿面传动误差、齿面最大应力。结果表明:采用的全齿面预控修形方法降低了圆弧刀廓加工齿轮副的传动误差幅值,提高了重合度,降低了齿面应力;并反求出优化设计后的机床加工参数,为实际生产中制造高重合度螺旋锥齿轮提供指导。     

Contouring algorithm for ion figuring

Ion beam figuring provides a highly deterministic method for the final precision figuring of optical components with advantages over conventional methods. The ion-figuring process involves bombarding a component with a stable beam of accelerated particles, which selectively removes material from the surface. The specific figure corrections are achieved by rastering the fixed-current beam across the workpiece at varying velocities. Unlike conventional methods, ion figuring is a noncontract technique that avoids such problems inherent in traditional fabrication processes as edge roll-off effects, tool wear, and force loading of the work piece. Other researchers have demonstrated that ion beam figuring is effective for correcting of large optical components. This work is directed toward the development of the precision ion-machining system (PIMS) at NASA's Marshall Space Flight Center (MSFC). This system is designed for processing small ( 10 cm diameter) optical components. The ion-figuring process involves obtaining an interferometric error map of the surface, choosing a raster pattern for the beam, and determining the velocities along that path. Because the material removed is the convolution of the fixed ion beam removal and the rastering velocity as a function of position, determining the appropriate velocities from the desired removal map and the known ion beam profile is a deconvolution process. A unique method of performing this deconvolution was developed for the project, which is also applicable to other mathematically similar processes, including computer-controlled polishing. This paper presents the deconvolution algorithm, a comparison of this technique with other methods, and a simulation analysis. Future research will implement this procedure at MSFC.     

化学刻蚀的光学元件面形修复

采用化学加工方法对光学元器件进行面形加工,可以避免传统的抛光工艺带来的亚表面缺陷和表面污染。实验中利用Marangoni界面效应有效控制化学液的驻留时间和驻留面积,并通过数控系统实现编程控制加工,进行了面形修复实验,利用轮廓仪测量了加工前后的表面粗糙度。结果表明,采用拼接小去除量多次加工的方法,有效地降低了面形误差,面形值由1.32 λ(λ=632 nm)减少到0.66 λ,粗糙度基本维持不变。利用此实验装置使基片面形得到修复,避免了传统加工方式带来的亚表面缺陷等问题,有利于强激光系统的使用。     

Optimization strategy for the velocity distribution based on tool influence function non-linearity in atmospheric pressure plasma processing

Atmospheric pressure plasma processing (APPP) is proved to be potential in the fabrication of optical elements with high efficiency and near-zero damage. However, high convergence rate in the figuring process is hard to achieve because of the tool influence function (TIF) non-linearity. Directly solved dwell time map by conventional deconvolution methods does not consider the non-linear thermal effect, which leads to significant figuring error. In this paper, the optimization strategy for TIF non-linearity based on the velocity distribution in APPP is presented. The exponential model of TIF with non-linearity is established by trench experiments. A series of simulations are also conducted to analyze the thermal effect of non-linearity on the figuring process, indicating the TIF constantly changes with velocity distribution. Two evaluation parameters, relative balance factor and velocity concentration factor, are proposed to investigate the figuring capacity of calculated velocity distribution. With two evaluation parameters, the optimization strategy of velocity distribution based on TIF selection is proposed to suppress the non-linearity. Verification experiments are carried out to validate the two optimized TIFs. The results show that high convergence is achieved to be 72.41% and 82.81% for root-mean-square value respectively, which proves the feasibility of the proposed optimization strategy.     

A swing arm method for profile measurement of large optical concave surfaces in the lapping process

Generally, optical components are fabricated by grinding, lapping, and polishing. Usually, these processes take a long time to obtain high surface quality. Therefore, in the case of large optical components, on-machine inspection (OMI) is essential, because the workpiece is fragile and difficult to set up for fabricating and measuring. This paper describes a swing arm method for measuring the surface profile of large optical concave mirrors. The measuring accuracy and uncertainty for the method are studied. Experimental results show that this method is especially useful in the lapping process, where an accuracy of 3–5 μm is obtained. Inspection data is also provided to correct the residual figuring error in lapping or polishing processes .     

Comparative studies of parameters calibration for focused ion beam deposition

This paper describes the interaction between operating parameters of target wafer surface. We use an organometallic (C) precursor gas in the focused ion beam deposition process. Under the beam intensity conditions (30kV), the influences of the on-target beam control parameters, such as dwell time, beam spacing, minimum frame time and scan type, were investigated by the deposition tests. The analysis was carried out with the variation of dimensions and shapes of the single pattern. The operating parameters considered in this research are implemented in the next double-patterning deposition. The test presented how their interaction appeared on the processing results. The analysis configured out the FIB induced deposition of single pattern with the variation of operating parameters. Additionally the result shows that the sequent beam job influenced the double-patterning deposition significantly. On-beam target conditions should be optimized for the target complicated shapes and high aspect-ratios     

用离子束溅射法制备长波段X射线多层膜

叙述了用离子束溅射镀膜机ＯＸＦＯＲＤ进行Ｘ射线长波段多层膜实验及制备Ｘ射线多层膜光学元件方面的工作。简述离子束溅射镀膜机的工作原理,Ｘ射线多层膜的制备过程,主要工艺参数,以及用Ｘ射线小角衍射仪对制备样品周期结构的检测和用软Ｘ射线反射率计测反射率的部分结果。     

大型X射线光学仪器:单层镜和多层镜的制造与表征

150~500 mm长度的各种X射线光学元件可用于光束导引,光束调整,以及单色化。本文介绍了两种不同的大型X射线反射镜。第一种为单层反射镜,这种反射镜以2°掠入射角在软X射线区(50~200 eV)起全反射镜作用,可用于自由电子激光器,如德国汉堡的FLASH。第二种是多层镜,由于它的布喇格反射特性,适于作为反射镜以0.4~1°的入射角用于硬X射线区(20~50 keV),如层析光束线的同步辐射存储环中。两种反射镜都用最新物理汽相淀积法制备,并用磁控溅射来实现X射线光学应用所需要的优良光学品质。这一淀积工艺使不同批次的镀膜稳定性良好,有利于实际反射镜在优质衬底上的最后淀积。单层镜和多层镜在它们的相关能量范围内都有很高的反射率,表面粗糙度也很低,且在整个光学波长区这些特性表现均匀。文中所叙相关研究都是借助X射线反射计量(XRR)法,透射电子显微镜(TEM)、光学轮廓仪(OP),以及原子力显微镜(AFM)完成的。