摘要
随着现代科技的不断发展,特别是装备性能的迅速提升,应用于各种领域的光学系统对关键零部件的精度要求越来越高。高精度球体类光学零件在精密测量仪器、激光核聚变和高精度陀螺仪表中有重要的应用,其技术对球面的形状精度要求非常高,成为制约其性能的关键因素。解决球体类零件三维误差测量及评价理论和高精度确定性修形工艺等关键性难题,为提高球体类零部件的制造水平提供理论支持和工艺基础,具有重要的科学意义和实际需求。
离子束修形技术以离子溅射效应去除材料,利用CCOS(Computer Controlling Optics Shaping)成型原理对面形进行误差修正,能够实现球体类零件的高精度加工。非接触、高确定性和纳米量级的材料去除方式使得离子束修形技术在很多方面都优于传统修形技术,沿曲面法向去除材料的特性和去除函数对表面曲率的不敏感性对于加工球体类零件具有明显的优势。本论文主要研究了子孔径拼接干涉测量方法,获得了球体类零件的全局面形误差分布,基于Sigmund溅射理论和CCOS成型原理研究了不同入射角离子束材料去除特性和面形误差修正技术等关键性问题,形成球体类零件离子束确定性修形的新方法和新工艺。论文的研究工作主要包括以下几部分:
1.以Sigmund溅射理论为依据,通过研究不同入射角下离子束修形过程中的材料去除特性,确定了去除速率与入射角的非线性关系,建立了相应的去除函数的理论和实验模型;揭示了不同入射角下离子束沿曲面法向去除材料的规律和去除速率对表面曲率的不敏感性,在离子源工艺参数恒定的条件下,推导出了去除速率是以入射角为单一变量的函数;研究了光学材料表面在离子束作用下的粗糙度演变过程,提出应用倾斜抛光和牺牲层抛光技术获得超光滑表面,延伸了离子束技术的加工性能。
2.基于CCOS成型原理,结合离子束修形的材料去除特性,针对高陡度镜面建立了驻留时间模型,对传统的卷积公式进行了改进,并介绍了该模型的加权Lucy-Richardson算法,提出了改进的脉冲迭代算法和基于补偿的驻留时间求解算法,解决了高陡度光学零件加工过程中驻留时间求解的难题。针对半球投影变形较大和全球面的不可展性,根据地球投影学的理论提出了面形的非线性展开和分带投影方法,并对划分的不同子区域进行拼接加工。
3.为了获得全局面形误差分布,解决高陡度球体类零件的测量和评价难题,研究了子孔径拼接干涉测量方法。针对不同的球体类零件设计了相应的位姿调节装置,实现了半球面和全球面的球体类零件的拼接干涉测量。通过地图投影原理对球体类零件的面形误差进行了三维重构,为离子束确定性修形技术提供了检测和评价手段。
4.在上述研究工作的基础上,对球体类零件进行了修形实验。形成了球体类零件离子束确定性修形的工艺流程,实现了以半球和超半球为典型代表的球体类零件的纳米精度制造,验证了驻留时间算法和工艺流程的可行性和正确性。
With the development of modern technology and especially the improvement of equipment performances, more and more higher precision is demanded on key optical components in various optical systems. High precision spherical optical components are playing important roles in precise measuring instruments, inertial confinement fusion systems and high precision gyroscopes, where the spherical form accuracy is required very high and becomes the critical factor responsible for system performances. How to measure and estimate the three-dimension (3D) surface error and develop deterministic and high-precision corrective figuring technologies come to be the key problems to be solved, which may provide theoretical support and technological foundation for improving the manufacture of the spherical optics. It is both scientifically and practically significant.
Ion beam figuring (IBF) provides an ultra-precision machining method for spherical optics based on the CCOS (Computer Controlling Optics Shaping) principle with the ion sputtering effect to remove material at atomic scale. It is deterministic, highly stable and non-contact with advantages over conventional figuring technology. The normal material removal characteristic and the removal function being insensitive to surface curvature make IBF advantageous for machining of spherical components. This thesis mainly discusses subaperture stitching interferometry to obtain the global surface error of spherical optics, and then addresses the key problems including the material removal characteristics and corrective figuring technologies according to Sigmund sputtering theory and CCOS principle, which forms a novel method and technology for spherical optics. The major research efforts include the following points.
1. Based on the Sigmund sputtering theory, the material removal characteristics at different incidence angles are studied to obtain the changing ruler of removal rate in dependence of different incidence angles and build the corresponding theoretical and experimental models of the removal function in IBF process. Meanwhile, the normal material removal characteristic and the removal function being insensitive to surface curvature are analyzed. When the process parameters of ion source are invariable, the deduced result shows that the removal rate is a function of the single variable of incidence angle. Based on the evolvement mechanism of surface roughness in IBF, the method of oblique-incidence figuring and sacrificial coating layer technology are proposed to obtain ultra-smooth optical surfaces. These figuring methods extend the machining capability of IBF.
2. Based on the CCOS principle and the material removal characteristics in IBF, the traditional convolution equation is revised to model the dwell time for high slope surface. Then the weighted Lucy-Richardson calculation method is introduced, and the modified pulse iterative method and the algorithm based on compensation are proposed to solve the model. Since the projection distortion of hemisphere is big and the full-sphere is undevelopable, the non-linear developing method and the zonal projection, according to cartographical theory, are applied for the stitching processing of the high slope spherical surfaces.
3. To solve the problems of measurement and evaluation of the spherical components, subaperture stitching interferometry is studied. The adjustment equipments are designed for various spherical components, and testing of hemispheres and full spheres are implemented. Then 3D surface error of spherical components is reconstructed via cartographical projection. These technologies provide IBF with measurement and evaluation method.
4. Based on above discussions, figuring experiments on spherical components were carried out to validate the feasibility of the proposed algorithm for dwell time and the effectiveness of the process flow. Finally nanometer-precision machining of spherical components was realized.
引文
[1] Saps Buchman,C.W.F. Everitt,Brad Parkinson,et al.Cryogenic gyroscopes for the relativity mission [J].Physica B,2000,280:497-498.
[2] Saps Buchman,C.W.F. Everitt,Brad Parkinson,et al.Gyroscopes and charge control for the relativity mission gravity probe B. Adv. Space Res.,2000,25(6):1181-1184.
[3] Michael Borys,Michael Gl?ser and Michael Mecke.Mass determination of silicon spheres used for the Avogadro project [J].Measurement,2007,40:785-790.
[4]孙新民,王占林,李树文等.四轴球体研磨机超精密研磨的机理及试验[J].河北理工学院学报,2000,22(1):41-46.
[5]晏磊,刘光军.静电悬浮控制系统[M].北京:国防工业出版社,2001.
[6] J. A. Lipa and G. J. Siddal.High precision measurement of gyro rotor sphericity [J].Precision Engineering,1980,26:123.
[7] Rupp W. J..The development of optical surfaces during the grinding process [J].Applied Optics.1965.4(6):743-748.
[8] Aspden R.,Mcdonough R.,Nitchie F. R..Computer assisted optical surfacing [J].Applied Optics,1972,11(12):2739~2747.
[9] Thomas W. Drueding,Thoms G. Bifano and Steven C. Fawcett.Contouring algorithm for ion figuring [J].Precision Engineering,1995,17:10-21.
[10] Wilson S. R. and Mcneil J. R..Neutral ion beam figuring of large optical surface [J].SPIE,1987,818:320-324.
[11] Canon technology highlights. www.canon.com.
[12] Haensel T.,Seidel P.,Nickel A. et al.Deterministic ion beam figuring of surface errors in the sub-millimeter spatial wavelength range [C].6th EUSPEN intl. conf. 2006,Baden,Vienna,Austria.
[13] Thomas Haensel,Andreas Nickel,and Axel Schindler.Ion Beam Figuring of Strongly Curved Surfaces with a (x,y,z) Linear Three-Axes System [C].Plasmonics and Metamaterials,OSA Technical Digest (CD) (Optical Society of America, 2008):JWD6.
[14]周林.光学镜面离子束修形理论与工艺研究[D].长沙:国防科技大学,2008.
[15]焦长君.光学镜面离子束加工材料去除机理与基本工艺研究[D],长沙:国防科技大学,2008.
[16]焦长君,李圣怡,解旭辉等.基于Bayesian原理的低陡度光学镜面面形误差离子束正驻留时间算法[J].机械工程学报,2009,45(11):253~259.
[17] Zhou L..Dai Y..Xie X..et al.Optimum removal in ion-beam figuring [J].Precision Engineering (2008),doi:10.1016/j.precisioneng.2009.12.002.
[18]刘金生.离子束技术及应用[M].北京:国防工业出版社,1995.
[19] Wolfhard M?oller.Fundamentals of Ion-Surface Interaction.http://www.fz-rossen- dorf . de/FWI.
[20] Peter Sigmund.Theory of sputtering Sputtering yield of amorphous and polycrys- talline targets [J].Physical Review,1969,184(2):383-415.
[21] Particle Interactions with Matter.www.srim.org.
[22] Bradley R. M. and Harper J. M. E..Theory of ripple topography induced by ion bombardment [J].J. Vac. Sci. Technol. A,1988,6:2390-2395.
[23]李兆泽,李圣怡,戴一帆等.磨料射流抛光中各工艺参数对材料去除率及抛光区域形貌影响[J].2008,21(19):2532~2535.
[24] N. Savvides . Surface microroughness of ion-beam etched optical surfaces [J].Journal of Applied Physics,2005,97(5):053517.1~ 053517.7.
[25] Changjun Jiao,Shengyi Li,and Xuhui Xie.Algorithm for ion beam figuring of low-gradient mirrors [J].APPLIED OPTICS,2009,48 (21),4090-4096.
[26] Lynn N. Allen and Henry W. Romig.Demonstration of an ion figuring process [J].SPIE,1990,1333:22-33.
[27] Inaba T,Kurashima Y..Low energy ion beam machining of ULE substrates: Evaluation of surface roughness [J].Microelectronic Engineering,2009,86:497-499.
[28] P. Gailly,J. P. Collette,C. Jamar,et al.Roughness evolution of some X-UV reflective materials induced by low energy ion milling [J].Nucl. Instr. and Meth. in Phys. Res. B,2004,216:206~212.
[29] Frost F.,Fechner R.,Ziberi B.,et al.Large area smoothing of optical surfaces by low-energy ion beams [J].Thin Solid Films,2004,459(1-2):100-105.
[30] Jacobs S. D.,Innovations in Polishing of Precision Optics.
[31] Axel Schindler,Thomas Haensel,Dieter Flamm,et al.Ion Beam and Plasma Jet Etching for Optical Component Fabrication [C].Pro. of SPIE,2001,4440:217-227.
[32] Jones R. A.. Optimization of computer controlled polishing [J]. Appled Optics, 1977, 16(1): 218-224.
[33]周林,戴一帆,解旭辉等.计算机控制光学表面成形中的频域分析[J].中国科学E辑, 2009, 39(3): 402-408.
[34]周林,戴一帆,解旭辉等.光学镜面离子束加工的可达性[J].光学精密工程,2007,15(2):160-166.
[35]邹谋炎.反卷积和信号复原[M].北京:国防工业出版社, 2001.
[36] Shanbhag P. M., Feinberg M. R., Ssndri G., et al.Ion beam machining of millim- eter scale optics [J].Applied Optics,2000,39(4):599-611.
[37]邓伟杰,郑立功,史亚莉等.基于线性代数和正则化法的驻留时间算法[J].光学精密工程,2007,15(7):1009-1015.
[38]周林,戴一帆,解旭辉等.离子束加工中驻留时间的求解模型及方法[J].纳米技术与精密工程, 2007, 5(2):107-112.
[39] ALLEN L. N.,KEIM R. E.. An ion figuring system for large optic fabrication [J]. SPIE, 1989, 1168: 33-50.
[40] Robert A. Jones and Wiktor J. Rupp. Rapid optical fabrication with CCOS [J]. Advanced Optical Manufacturing and Testing, SPIE, 1990, 1333, 34-43.
[41] A. Schindler, T. Hansel, F. Frost, et al. Ion Beam Finishing Technology for high Precision Optics Production [C]. OSA/OFT (2002), OTuB5-1.
[42] William H. R..Bayesian-Based Iterative Method of Image Restoration [J].JOSA,1972,62:55-59.
[43] Kong X.,Li Y.,Yuan X.,et al,Restoration of pinhole images using Lucy-Richard- son algorithm [J].Acta Physica Sinica,2006,55(5):2365-2370.
[44]王贵林.SiC光学材料超精密研抛关键技术研究[D].2002,国防科技大学,长沙.
[45]周旭升.大中型非球面计算机控制研抛工艺方法研究[D].2007,国防科技大学,长沙.
[46]王家耀,孙群,王光霞等.地图学原理与方法[M].北京:科技出版社,2006.
[47]祝国瑞.地图学[M].武汉:武汉大学出版社,2004.
[48]丁凌艳,戴一帆,陈善勇.平面子孔径拼接测量研究[J].光学精密工程,2008,16(6):978-975.
[49]陈善勇,戴一帆,解旭辉等.子孔径拼接干涉测量的精度估计方法[J].光学学报,2008,28(5):883-888.
[50]曾生跃.子孔径拼接工作站设计及其关键技术研究[D],2008,国防科技大学,长沙.