| 题名 | 高精度非球面数控加工工艺研究 |
| 作者 | 张逸中 |
| 学位类别 | 硕士 |
| 答辩日期 | 2015 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 邵建达 |
| 关键词 | CCOS 非球面 柔性小工具 中高频误差 光顺加工 |
| 其他题名 | Study on Techniques in Computer-controlled Processing for High-precision Aspheric Surfaces |
| 中文摘要 | 非球面元件是一种非常重要的光学元件，不仅能够有效的矫正多种像差，改善成像质量，提高系统相对口径，扩大视场角度；还能够以一个或几个非球面元件代替多个球面元件，有效的简化系统结构，减轻仪器重量。因此，非球面元件被广泛的应用于各种现代光学系统中。随着光学技术的快速发展，现代超精密光学系统对非球面元件的精度要求和数量需求也越来越高，传统手工修抛的方式已无法满足这些日益增长的需求，对计算机控制小工具成型(Computer Controlled Optical Surfacing, CCOS)的数控加工技术提出了更高的要求。目前国内外采用的CCOS理论基础大多都是基础Preston方程的，而传统的数控小磨头加工非球面的技术仍存在一些问题需要解决，如小磨头与非球面表面吻合、工件表面中高频误差控制等。这些问题的存在都严重影响了非球面光学元件的加工效率和加工精度。本论文为提高非球面加工效率和加工精度，实现高精度的非球面数控加工工艺，就以上问题展开了相应的研究，其主要内容包括： 1、设计并制作了两种不同类型的柔性抛光小工具，分析介绍了选取粘弹性非牛顿流体材料作为小工具柔性层的理论依据及其满足非球面曲率变化的原理。同时，还分析了柔性抛光小工具盘下的压力分布情况，并结合Preston方程阐述了柔性抛光小工具实现材料去除的原理：抛光区域内高点去除量要大于低点去除量，从而实现非球面表面面形收敛。最后分析说明了传统的非球面加工路径在加工过程中产生中高频误差的原因，并在传统加工路径的基础上，通过引入权值因子的方法优化了螺旋加工路径。 2、通过实验结合理论分析了抛光盘对中高频误差的修正能力，并发现：中高频误差收敛呈指数衰减；小磨头采用自转运动方式对中高频误差的修正能力要优于行星运动方式和平转动运动方式，并且自转速度越高，中高频误差收敛速度越快；同时比较了传统沥青盘和上述所制作的保型盘对中高频误差的修正能力，得到了抛光盘刚度越大，收敛效率越高的结论。最后通过计算机仿真优化了整个光顺加工过程，给出了当抛光盘半径为15mm时，中高频误差修正的最优速度比范围。 3、通过使用数控小工具机床结合磁流变机床实现了150mm非球面的研抛工艺，并有效的解决了研磨过程中出现的镜面像散问题。同时成功地将所设计的保型盘应用到了非球面的光顺过程中，最终面形精度为PV=λ/4，RMS=λ/40。 4、基于150mm非球面的研抛实验的加工经验，提出了一种全频段高精度非球面的加工方法。该方法通过使用柔性盘取代传统刚性盘进行镜面抛光，并使用变步距的螺旋加工路径来控制加工过程中所引入的中高频误差，最终成功的实现了仅使用CCOS数控小磨头机床便实现了其他组合加工方法所能达到的加工精度，完成了全频段高精度非球面的制造工艺。实验中的非球面最终面形精度为PV=0.188λ、grms=λ/50/cm、表面粗糙度Rq=0.9nm。 |
| 英文摘要 | Aspheric optics are being more and more widely used and play an important role in modern optical systems, due to their ability of correcting aberrations, enhancing the image quality and enlarging the field of view, while simplifying the system structure and reducing the weight and volume of the system. With the rapid development of modern optical technology, requirements for aspheric optical components are more and more critical. As the traditional manual polishing method has been unable to meet the growing demands, more emphasis are put on the computer controlled optical surfacing (CCOS) techniques. So far, internationally used CCOS technique is based on Preston equation, however, there are also some problems in CCOS to get an aspheric surface, such as how to make the tool fit the surface and how to control the mid-to-high spatial frequency errors. These problems have influenced machining accuracy and efficiency of optical components seriously. In order to improve the efficiency and accuracy of aspheric surface, and to achieve high-precision aspheric CNC process, the problem mentioned above are studied in this paper, which include: 1. Two kinds of flexible tools are designed to fit the aspheric surface which use a visco-elastic non-Newtonian fluid material. Meanwhile, analyzes the pressure distribution under the flexible tool and combined with the Preston equation to describe the material removal principle of flexible tools. At the same time, analyzing the impact of the traditional path on mid-to-high spatial frequency errors and optimizing the polishing path. 2. Analyzing the effect of polishing laps on the capability about correcting mid-spatial-frequency errors, which can be concluded: The converge of mid-to-high spatial frequency errors is exponential decay; The spin motion is better than other tool motion; Smoothing efficiency is proportional to the speed ratio: the faster the spinning speed is, the higher the smoothing efficiency is; When the radius of the polishing tool is kept as 15 mm, the optimal speed ratio range is 0.01≤f≤0.09. 3. Grinding and polishing the 150mm aspheric surface with CCOS and MRF, and effectively solves the problem of mirror astigmatism in grinding process. At the same time, successfully applied the flexible tool which mentioned above to the process and the final surface errors is PV=λ/4,RMS=λ/40. 4. Introduced an approach to get a full-spectrum high-precision aspheric surface which contains using a flexible tool and a novel polishing path. The effectiveness of this method is verified by the experiment on a 200mm aspheric surface. At last successfully obtain a full-spectrum high-precision aspheric surface which final surface errors is PV=0.188λ,grms=λ/50/cm and Rq=0.9. |
| 语种 | 中文 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/16902]  |
| 专题 | 上海光学精密机械研究所_学位论文 |
| 推荐引用方式 GB/T 7714 | 张逸中. 高精度非球面数控加工工艺研究[D]. 中国科学院上海光学精密机械研究所. 2015. |
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