【作者】 焦长君；

【导师】 李圣怡；

【作者基本信息】 国防科学技术大学 ， 机械工程， 2008， 博士

【摘要】 光学系统性能要求随着科技的发展不断提高,观测系统、激光系统、光刻投影系统等技术的发展,对光学零件的需求激增,且技术要求较传统光学零件也有很大提升,突出体现在对大口径、大相对口径非球面、轻质薄型、离轴非球面等光学零件的全波段(有效口径内波前的各种空间频率成分)面形误差提出了严格要求。如何高效地加工出高精度光学零件是光学制造业必须解决的关键问题。离子束加工方法以离子溅射效应形成去除函数,利用CCOS(Computer Controlling Optics Shaping)成型原理对低频面形误差进行修正。非接触式的材料去除方式消除传统方法无法避免的边缘效应和工具磨损等问题,工艺过程高的确定性以及原子尺度的材料去除能力使得其成为高精度光学镜面最有希望的解决方案之一。本文从Sigmund溅射理论和CCOS成型原理出发,研究离子束加工中材料去除机理以及面形误差修正技术等方面的关键问题,以形成光学镜面离子束加工技术理论基础和工艺方法。论文的研究工作包括以下几个部分:1.从CCOS原理和Preston原理归纳出修形工艺中去除函数以及成型原理方面的一般性问题;基于CCOS原理,对离子束加工系统—KDIFS-500进行结构、功能和精度设计。建立加工系统的DH运动学模型,根据此模型对系统进行误差分析,并提出误差补偿和控制策略,给出加工系统的后置算法。2.基于Sigmund溅射理论,建立离子束加工过程特征指标—材料去除效率、扰动层厚度以及热效应与工艺参数之间的关系模型,在此基础上进行仿真和实验研究,建立工艺过程参数优选的理论基础。在对离子束修形过程进行抽象的基础上,基于Sigmund溅射理论和曲面局部结构理论,建立去除函数理论模型,分析去除函数的特征,并进行实验研究。基于CCOS成型原理,利用Hermite级数和Fourier级数,建立描述成型过程的双级数模型,进而分析工艺过程中去除函数扰动、测量误差、定位误差以及离散间隔对工艺过程的影响。此研究形成离子束加工工艺参数控制策略,并为修形工艺路线确定提供理论支撑。3.实验研究离子束加工后工件表面粗糙度随离子入射能量、材料去除深度等参数的变化关系,观察离子束加工后表面出现的特征结构,结合光学材料研抛阶段的亚表面损伤形成机理,分析表面粗糙度变化的原因。4.根据CCOS成型原理,结合驻留时间近似速度实现方式误差模型,建立基于Bayesian原理的驻留时间迭代算法,算法的正定性解决了驻留时间必须为正的问题。以此算法为基础,结合去除函数特征和路径规划,将低陡度曲面加工过程进行平面化近似,形成曲(平)面全口径加工统一的面形误差修正方法。在对去除函数回转对称处理基础上,将极轴修形过程近似成线性过程,以利用全口径方式Bayesian迭代算法求解驻留时间,通过在极轴加工方式中引入反映面形局部特征的驻留时间速度实现方式,解决了极轴方式修正非回转对误差的问题,形成面形误差极轴加工方式修正方法。以CCOS原理为基础,建立拼接加工过程的有限域非线性模型,并据此对Bayesian迭代算法进行相应改进后用于求解拼接加工驻留时间,针对对刀误差对拼接加工的影响,结合离子束加工的确定性,提出了误差“辨识—补偿”策略,最终形成面形误差拼接加工方式修正方法。5.在上述工作的基础上,结合常规CCOS方法的工艺流程,提出离子束全口径扫描加工方式、极轴扫描加工方式以及拼接扫描加工方式的工艺流程。通过对平面、球面以及非球面等镜面的修形的实验研究,验证工艺流程的可行性和正确性。工艺方法的显著特点是通过工艺参数”辨识—补偿”的闭环校正控制提高工艺系统的效率。更多还原

【Abstract】 The performance demands of the optics system increase with the development ofscience and technology. The developments of the optical observation system, laser weaponsystem and lithography system improve the requirement of the optics components, andthe technical requirements for optics components of these systems are improved comparedto conventional systems. Especially, modern systems need mirrors of large aperture, largerelative aperture, light-weighted, thin and o?-axis. The residual surface error of mirrorsused in these systems should be controlled within the full range (all spatial frequencycomponents of wavefront in the clear aperture of the mirror) strictly. How to manufactureoptics components of high precision with high e?ciency comes to be the key problem ofthe optics manufacturing to be settled. With the near-Gaussian removal function deducedfrom the ion sputtering mechanism, the low frequency errors of the optics mirror arecorrected according to the CCOS principle. The material removal is in the nanometerscale. Due to non-contact between the tool and the workpiece, the edge-e?ect and tool-wear problems involved in the conventional process are avoided. Ion beam figuring processis of high determinacy and of high e?ciency. All these properties make ion beam figuring beone of promising methods for mirrors of high precision. In order to form the fundament ofion beam figuring technology and process, this thesis is dedicated to solving key problemsin the material removal mechanism and surface error correcting technologies with theSigmund sputtering theory and CCOS principle. The major research e?orts include thefollowing points.1. The common problems about the removal function and shaping principle are deducedfrom the CCOS and Preston principle. Based on CCOS principle, the ion beammanufacturing system—KDIFS-500 is designed from the aspects of structure, functionand precision. With the DH kinematics model of KDIFS-500, the error transformingmodel is built. Based on the error model, the strategy of error compensation andcontrolling is presented, and the post-processing algorithm of KDIFS-500 is deduced.2. Based on the Sigmund sputtering theory, the relation models between the propertyfactors such as material removal e?ciency, disturbance depth and thermal e?ect andprocess parameters of the ion beam figuring are built. Simulation and experimentsare carried out to validate these models. With these discussions, the optimizationfundament of process parameter comes into being. Based on the abstract of ion beamfiguring process, the removal function models are built. The properties of the removalfunction are deduced from these models. Experiments are carried out to validate theseproperties. Based on the CCOS principle, the Hermite-Fourier model of the figuringprocess are built. With this double-series model, the e?ects of the removal functiondisturbance, measure error, positioning error and discrete interval on the figuringprocess are analyzed. These discussions form the fundaments of process parameter controlling strategy and the choice of process route.3. The relation among the roughness evolution of mirrors after ion beam bombardment,the energy of the incidence ion and the removal depth are analyzed with experiments.The characteristic microstructures of the sputtered surface are discovered. Combinedwith the sub-surface damage model during the conventional lapping and polishing,the cause for the roughness evolution is discussed.4. Based on the CCOS principle and the realization error model of the dwell time inthe approximated velocity mode, Bayesian-based iterative algorithm for planar mir-rors is deduced. The non-negativity of the iterative algorithm makes sure that thedeconvoluted dwell time be greater than zero, which is demanded in the figuring pro-cess. Based on properties of the removal function, the shaping process of low gradientmirrors can be approximated to be the linear model for planar mirrors. With thesediscussions, the unified error surface controlling technology for planar and low gradi-ent mirrors with full-aperture linear scanning mode is set up. By the circular averagedealt with the removal function, the figuring process with spiral scanning path canbe simplified to a linear one and be described by conventional CCOS principle. Withthe Bayesian-based iterative algorithm, the dwell time is deconvolued. The dwelltime is realized on a spiral path with varied rotative velocity. With these methods,the ion beam figuring technology with spiral scan mode comes into being. Based onCCOS principle, the finite field non-linear model is deduced from the stitching shapingmechanism. With the superposition property in the model, a modified Bayesian-baseiterative algorithm is presented to deconvolute the dwell time for the stitching process.The e?ect of the positioning errors and the removal rate on the machining accuracyand shape is modeled and then the identification and compensation algorithm forthese parameters is proposed based on this model. With these studies, the stitchingfiguring technology comes into being.5. With the discussions above, the unified ?ow chart for full-aperture linear scanningmode, polar scanning mode and stitching scanning mode is presented based on the con-ventional process. Figuring experiments on planar, spherical and aspherical mirrorsvalidate the e?ectiveness and correctness of the ?ow chart. With the closed loop con-trol technology provided by the process parameter“identification—compensation”step,the process e?ciency can be very high, which is the obvious character of the ?ow chart.更多还原