单点金刚石机床及其在光学工程领域的应用

介绍了单点金刚石车床概念,总结回顾了单点金刚石车床在国防和商业领域内的发展状况,给出了目前商用单点金刚石车床的典型产品。对单点金刚石车床的关键零部件和核心技术,如空气静压主轴、液压导轨、直流电机、对刀装置、误差补偿和自适应控制等进行了分析。最后,介绍了适宜单点金刚石车削加工的材料,分析了快刀伺服和慢刀伺服在光学元件中的应用以及所加工的光学元件在国防和商用光电产品中的应用,并以主次镜望远镜系统和精密光学系统无调整装配为例,说明了单点金刚石车削在光电产品中的重要作用。     

单点金刚石精密数控车削加工技术及发展前景分析

针对我国红外热像仪、探测仪及惯性约束核聚变工程对红外晶体类光学元件的需求,开展了单点金刚石精密数控车削加工技术的研究,分析了单点金刚石精密数控车削加工技术的特点及应用范围、机床整体布局及主体结构型式。介绍了该项技术在国内外的发展现状和趋势,对该项技术的应用发展前景进行了分析和预测。在消化和引进国外先进制造技术和最新研究成果的基础上,突破单点金刚石精密数控车削加工的关键制造技术,解决了我国光学非球面精密数控车削加工技术和设备依赖引进的问题,实现了单点金刚石精密数控车削加工技术及设备的国产化,提高了我国红外光学元件的精密加工技术水平和设备制造能力。     

衍射光学元件车削补偿技术的研究

超精密单点金刚石车削加工是高精度衍射光学元件制造的重要方法,但是以往的加工方法是直接一次车削加工成型,无法实现具有加工-检测-补偿加工-检测的闭环控制特点的超精密加工,从而导致零件精度较低。针对这种加工技术的缺陷,通过研究衍射光学元件金刚石车削过程和面形状误差补偿,对表面轮廓仪实际测量的轮廓数据进行处理,计算出实际车削曲线与理想曲线之间的法向残余误差,以此获得新的金刚石车削加工轨迹,实现衍射光学元件的超精密闭环控制加工。利用单点金刚石车床对口径78的衍射光学元件进行补偿加工试验,最终使其PV值由10.4 m经过一次补偿加工后降为4.3 m。     

单点金刚石车削加工切削距离的计算

讨论了大型金属反射镜在金刚石车削中,金刚石刀具的磨损对加工精度的影响;详细介绍了超精密加工中几种典型零件形状单点金刚石车削加工的切削距离计算方法,经计算在加工直径为1000mm的圆盘工件时,当刀具的进给量为2μm/r,切削距离达到近400km。通过计算为加工大型光学元件刀具磨损规律的研究提供分析基础。     

衍射元件表面粗糙度对衍射效率的影响

基于多层衍射光学元件的位相延迟表达式,提出了单点金刚石车削影响下的多层衍射光学元件衍射效率和带宽积分平均衍射效率的数学模型,并给出了相应的分析表达式.以基底材料分别是硒化锌和硫化锌构成的多层衍射光学元件在近红外波段(1.4~2.5m)的应用为例进行分析.结果表明表面粗糙度会导致多层衍射光学元件衍射效率和带宽积分平均衍射效率的明显降低,从而降低了混合成像光学系统的成像质量.因此,单点金刚石车削衍射元件时,要根据使用需求制定合理的表面粗糙度加工误差.     

光学零件的金刚石车削

本文着重介绍了光学零件用单点金刚石车削的加工原理、加工工艺和应用范围,以及该工艺的特点。     

铝合金表面的直接光学抛光实验

单点金刚石车削铝合金表面具有较好的表面质量和精度,但车削纹路会产生散射现象,难以满足高品质光学系统要求。对铝合金表面进行直接光学抛光可以去掉表面产生的车削纹路,提高反射表面的光学性能,分析酸性条件下和碱性条件下的铝镜抛光原理,采用新型抛光盘与抛光液对单点金刚石车削后铝合金表面进行抛光实验。实验结果表明:通过合理控制工艺参数,能够消除铝合金表面残留的周期性车削刀纹,并且不会产生新的表面划痕,得到较好的铝镜光学表面质量,测得的铝镜表面粗糙度Ra=2.6 nm。     

单点金刚石超精密车削快点火靶丸微孔精度控制北大核心CSCD

研究了单点金刚石超精密车削技术(SPDT)加工靶丸微孔中的精度控制方法,建立了靶丸微孔加工误差的仿真模型,并理论分析了不同误差因素对微孔尺寸误差的影响规律;根据误差分析结果提出了基于刀具阶梯进给运动方式的微孔精度控制方法,用以控制靶丸微孔精度;在单点金刚石超精密车床上进行了辉光放电聚合物(GDP)靶丸微孔的车削实验,实验结果表明:采用该精度控制方法,靶丸微孔尺寸误差和圆度误差分别降低了70.7%和87.5%,实验结果表明了所提出方法的有效性。     

纳米级光学超精密加工技术

纳米级光学超精密加工是软X射线光学和光电子学元件制备的重要基础技术之一。本文概述这一技术研究的主要内容并介绍近10年来特别是80年代后期在这一研究领域的最新进展，例如单点金刚石车削、可延展磨削、浮法抛光以及离子束抛光等。超精密加工的最终目标是直接操纵原则，本文还介绍了用扫描隧道显微镜（STM）实现亚纳米级超精密加工的可能性。亚纳米级超精密加工技术将成为下个世纪重要的高技术。     

小口径非球面加工技术及装备综述

小口径非球面零件是一种非常重要的光学零件。介绍了国内外小口径非球面超精密加工技术的发展现状和装备。对单点金刚石车削、超精密磨削、透镜成型、超精密铣削和特种加工技术进行了综述。指出了小口径非球面加工的发展趋势和产业化需要解决的问题。     

Development of a double-sided micro lens array for micro laser projector application

This paper introduces the development of a double-sided micro lens array (DSMLA) for application in micro laser projectors. For commercial mass production, it is necessary to investigate the concurrent engineering of optical design, mold fabrication, and plastic injection molding at once. This experiment based the design of the micro lens array on the scalar diffraction theory. The proposed DSMLA can simultaneously shape red, green, and blue laser beams into a uniform projection pattern. An ultra precision diamond turning machine using a slow tool servo method fabricated the mold. The study considered optical design constraints from the feedback of mold fabrication and plastic injection molding, measuring and comparing fabricated samples with calculated results. Experimental results show that the fabricated DSMLAs achieve the desired function and application feasibility for micro laser projectors.     

基于机器视觉的刀具轮廓在线检测方法的研究

超精密单点金刚石车削过程中需要对刀具参数进行检测。基于机器视觉原理,采用新型的机械结构设计了新型刀具在线检测系统。通过垂直放置的两组由同轴远心镜头和CMOS相机组成的光学系统来获取车刀刀尖正面及侧面的图像,再经图像处理系统来获取刀具的轮廓及位置信息,完成对刀具轮廓及位置的在线检测,实验验证可实现测量的重复性定位精度达1μm。在线检测的方式借助了超精密车床自身的高精度和运动机构,可以保证相机焦点和机床主轴之间的相对位置关系,弥补了目前刀具检测系统稳定性差和重复性精度低的不足,提高了加工的整体效率。     

Design and fabrication of a microlens array by use of a slow tool servo

In recent years it has become possible to fabricate free-form optics by use of multiaxis ultraprecision machines. Here a 5 x 5 microlens array is fabricated by using an ultraprecision diamond turning machine equipped with four independent axes. Unlike the conventional process where a single diamond tool is used to machine one lens at a time, this research demonstrates the development of an innovative diamond tool trajectory that allows the entire microlens array to be machined in a single operation. The machined microlens array is measured for both curve conformity and surface roughness. Compared to the conventional approach where indexing the workpiece is difficult and unreliable, this process can produce microlenses with accurate geometry and optical surface finish. This unique process is described in detail from optical measurement to machining process design and development to final results. This research also demonstrates the possibility of fabricating any arbitrary shape with the same approach.     

多模调制曲面超精密加工轨迹优化技术

研究了采用单点金刚石超精密车削加工技术(SPDT)加工多模调制曲面过程中的刀具轨迹优化方法,首先,分析了SPDT方法加工多模调制曲面的基本原理;其次,理论分析了平行弦双圆弧插补算法的基本原理,推导了插补误差计算公式。在此基础上,提出采用插补步长伸缩变化方式实现了插补误差的动态控制,并获得了完整的插补计算公式;最后,采用Matlab软件对该插补算法进行了实例仿真分析,并分别与直线插补算法和固定步长双圆弧插补算法进行了对比分析,结果表明,该方法能在保证插补允差的前提下最大程度的减少插补区间数,从而有助于提高加工效率和延长刀具寿命。该方法在调制靶金属模板的制备中获得了广泛应用。     

Airborne sound emission as a process monitoring tool in the cut-off grinding of concrete

A detailed analysis of the airborne sound emitted in the cut-off grinding of concrete with a diamond grinding disk is presented. It is shown that the frequency spectra of airborne sound emitted in the cutting process contain detailed information about the process conditions. As long as the machining parameters are appropriate for the work piece, the airborne sound spectra show statistically excited natural frequencies and turning frequencies. In this case the total signal level gives sufficient evidence of the work piece composition and machinability. The effects of inappropriate machining parameters, like tool deflection or very high friction forces acting on the tool, can be identified by means of distinct frequencies in the airborne sound spectra. In addition, the emitted airborne sound can be used to image the structure of the flat joint surface, which cannot be determined by another method. With regard to everyday applications, the results obtained by this procedure can be used to apply airborne sound analysis systems to machines and detect process parameters which are overstressing the cutting tool.     

Ring beam shaping optics fabricated with ultra-precision cutting for YAG laser processing

In this study, a method for generating ring intensity distribution at a refraction-type lens with an aspheric element was proposed, and the beam shaping optical element was finished using only ultra-precision cutting. The shape of the optical element and its irradiance pattern were determined from numerical calculation based on its geometrical and physical optics. An ultra-precision lathe was employed to fabricate beam shaping optical elements, and acrylic resin was used as the material. The transmittance of an optical element (a rotationally symmetrical body) with an aspheric surface fabricated using a single-crystal diamond tool was over 98%, and its surface roughness was 9.6 nm Ra. The method enabled the formation of a circular melting zone on a piece of stainless steel with a thickness of 300 μm through pulse YAG laser (λ 1:06 μm) processing such that the average radius was 610 μm and the width was 100–200 μm. Circular processing using a ring beam shaping optical element can be realized by single-pulse beam irradiation without beam scanning.     

KDP光学零件超精密车削加工误差的频谱特性与控制

超精密车削技术适于加工KDP(磷酸二氢钾)等频率转换类型的强光光学零件,但车削表面存在明显的加工纹理,导致抗激光损伤阈值降低。以加工表面误差幅值及其频谱分布为对象,分析了KDP光学零件超精密车削的加工特征和误差形态,采用功率谱密度(PSD)评价方法研究了工艺参数与误差频谱的内在关系,结果表明:不同进给速度及主轴转速将使螺旋形刀痕的间距发生变化,进而影响KDP表面误差的频率成分;切削深度虽然对误差频谱影响很小,但会改变PSD的幅值;当主轴转速高于500 r/min、进给速度小于2 mm/min、切削深度小于2 μm时能够加工出rms值优于20 nm的KDP面形。在此基础上,以典型KDP光学零件加工为例,通过超精密补偿车削方法将低频误差的PSD控制在300 nm2·mm以内,中高频误差的PSD控制到国家点火装置(NIF)标准线以下,满足强光系统的工作要求。