| 题名 | 大口径光学平面镜低阶面形检测技术研究 |
| 作者 | 戚二辉 |
| 学位类别 | 博士 |
| 答辩日期 | 2015-05 |
| 授予单位 | 中国科学院大学 |
| 导师 | 张新 |
| 关键词 | 光学检测 大口径平面镜 低阶面形 轮廓检测 |
| 其他题名 | Study on Low Order Aberrations’ Testing Technology for Large Optical Flat Mirror |
| 学位专业 | 光学工程 |
| 中文摘要 | 随着科学技术的发展，大口径光学系统在空间光学、天文光学等领域得到了迅速发展。大口径的平面镜作为大口径望远镜系统的折返镜、大口径干涉仪的透射标准镜以及部分光学系统自检验的标准反射镜，其口径也在不断增大。以国际合作的三十米地基望远镜（Thirty Meter Telescope-TMT）项目为例，TMT的三镜（M3M）为一个超大口径椭圆形平面镜，口径尺寸达到前所未有的3.5m×2.5m。 大口径光学系统对大口径光学平面镜的面形精度有很高的要求，需要有高精度的检测手段来实现面形检测。对于M3M量级的超大口径光学平面，传统的检测手段如三坐标测量机(Coordinate Measuring Machine-CMM)，Ritchey-Common检测，子孔径拼接等，很难同时满足系统对测量精度，检测成本，检测效率的需求。如何高效率的实现大口径平面镜的高精度面形检测，尤其是低阶面形误差的测量是光学人员面临的难题。本文在实验室已有工作的基础上，主要开展了以下几个方面的工作： 一、大口径平面镜研磨阶段在线轮廓检测技术研究。针对传统的三坐标等轮廓测量方法对大口径工件测量精度低，测量周期长等问题，提出基于斜率测量的双测头轮廓测量方案：采用两个高精度非接触式位移传感器对大口径平面镜进行面形斜率测量，进而对面形斜率数据进行最小二乘法处理，获取整个镜面的低阶面形信息。采用双测头斜率测量方式，可避免检测过程中位移传感器测量不确定度的误差累积，降低系统测量对高精度导轨的依赖，使用普通的机床设备即可达到很高的检测精度。 二、双测头轮廓仪的研制。结合现有加工设备，完成双测头轮廓仪的结构设计、控制系统设计、系统装调与标定、测量路径规划与数据处理等工作。以M3MP（TMT三镜的原理样镜，600mm×900mm）为检测样本开展双测头轮廓仪检测实验，实验结果显示，双测头轮廓仪与三坐标测量机的检测一致性可以达到0.05μm rms，满足大口径平面镜研磨阶段的在线轮廓检测需求。 三、五棱镜扫描检测技术的相关理论分析。选择五棱镜扫描检测技术作为大口径平面镜抛光阶段的低阶面形检测手段，基于矩阵运算的光线矢量追迹方法，建立五棱镜扫描检测系统的数学模型，对各误差源影响系统测量精度的形式及量级进行了评估，完成系统的精度分析。对于非圆形大口径平面镜，常用的最小二乘法拟合算法进行数据处理时会出现奇异值，最终会造成求解失败，针对这一问题,提出采用基于多项式内积和cholesky分解的矩阵运算的方法进行数据处理，可适用于任何非圆形面域的检测，并结合TMT三镜的原理样镜M3MP完成了模拟检测实验，相关研究成果已顺利通过TMT项目组的前期评审。 四、五棱镜扫描检测系统研制。结合TMT项目需求，完成五棱镜扫描检测系统的结构设计、运动控制及数据采集等工作；利用实验室现有实验设备与测量仪器，实现五棱镜扫描检测系统的主要部件，包括自准直仪、五棱镜、三维调整架、高精度导轨、闭环控制等部分的精度标定，验证了系统工作可靠性；完成系统高精度装调，对现有的Φ300mm标准平面镜展开实验，实验结果显示，系统对300mm平面镜低阶面形的检测精度可优于60nm rms，单点测量不确定度优于0.1″，可满足大部分平面镜对抛光阶段低阶面形误差的检测需求。 五、相关检测技术在大口径平面镜加工过程中的应用研究。本文结合相关检测技术，确定了大口径平面镜不同加工阶段的检测方案，在此基础上结合CCOS控制平转动大磨头技术，提出大口径平面镜的加工策略，并将其用于指导M3MP的实际加工过程。目前已完成M3MP的背面研磨及抛光，正面已加工至初步抛光阶段，加工过程中单次加工收敛率可达56%，证明本文提出的加工策略在大口径平面镜的加工中是行之有效的。 |
| 英文摘要 | With the development of science and technology, optical system with large aperture is rapidly expanding in space optics, astronomy optics and other fields. The flat mirror’s size is larger and larger, and could be used as reflection mirrors in big telescope systems, transmission lens of large interferometer, and standard mirror in some optical system. Taking the Thirty Meter Telescope-TMT project as an example, TMT’s tertiary mirrors (M3M) is an elliptical flat mirror, whose size is up to 2.5 m × 3.5 m. The large aperture optical system has high requirements on surface accuracy, and high-accuracy test method is needed. For the extremely large M3M, the traditional methods such as CMM, Ritchey-Common, sub-aperture stitching etc. are difficult to simultaneously meet the demand of testing accuracy, cost, and efficiency. How to test the large flat mirror efficiently and accurately, especially the test of low order surface errors, is difficult. Our primary work is as follows: 1) Research on online profile measuring technology for grinding large flat mirror. Traditional profile measurement methods such as CMM have disadvantages like low measurement accuracy, and long measurement cycle. In this thesis, a novel dual-gauge profilometer is presented. The entire low order surface profile is achieved from surface slope which is tested by two high-precision non-contact displacement sensors, by least square method. The error accumulation of uncertainty caused by displacement sensor could be avoided by using dual-gauge slope measurement, so the testing system has low dependence on highly accurate rail. A highly accurate testing result could be achieved by ordinary machine. 2) Development of dual-gauge profilometer. The design of structure and control system, system alignment, precision calibration, measurement path and data processing are completed combined with previous theory, as well as the machine’s structure and motion feature. M3MP (a prototype of TMT’s tertiary mirrors, 600mm × 900mm) was tested by the proposed dual-gauge profilometer. The difference of the testing result between the proposed method and CMM is 0.05μm rms, which satisfies the accuracy demand for large flat mirror’s online profile measurement. 3) Theoretical analysis of scanning pentaprism technology. Scanning pentaprism technology could be as a testing method of low order profile during the polishing process of large flat mirror. In this dissertation the scanning pentaprism system’s mathematical model is built, based on ray tracing vector method of matrix manipulation. The form and order of testing accuracy influenced by various error sources are evaluated. For non-circular large flat mirror, singular value will be caused by the traditional least squares fitting algorithm, which results in the failure of the data fitting. In order to solve this problem, a method combining the inner products of polynomials and cholesky decomposition is adopted, which can be applied to arbitrary non-circular aperture. A simulated testing is performed on M3MP, and the relevant results have passed the preliminary review or TMT project. 4) Development of the scanning pentaprism system. According to the demands of TMT project, structural design, motion control, and data acquisition of the scanning pentaprism system have been completed. System’s main components, including the auto-collimation, pentaprism, 3D adjustor, high precision optical rails, feedback control are carefully calibrated in our laboratory to verify the system’s reliability. A Φ300mm standard mirror was tested by the well aligned scanning pentaprism system. The experimental results show that the testing precision of 300 mm mirror’s low order aberrations could be 60nm rms, system’s measurement uncertainty for single testing point can be better than 0.1 arcsec, which satisfies the testing requirements of low order aberrations during polishing flat mirror. 5) Application of relevant testing technologies in large flat mirrors’ manufacturing process. Combining with relative testing methods, this thesis confirms the testing strategy for large flat during different phases, then an manfactouring strategy based on CCOS technology is presented for manufacturing large flat mirrors. The proposed strategy is used to guide the actual manufacture process of M3MP. Up to now, the whole polishing of M3MP’s back surface and preliminary polishing of its front surface has been completed. The surface convergence rate can be up to 56% in a single processing, proving the efficiency of proposed strategies in manufacturing large flat mirrors. |
| 公开日期 | 2015-12-24 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.ciomp.ac.cn/handle/181722/48886]  |
| 专题 | 长春光学精密机械与物理研究所_中科院长春光机所知识产出 |
| 推荐引用方式 GB/T 7714 | 戚二辉. 大口径光学平面镜低阶面形检测技术研究[D]. 中国科学院大学. 2015. |
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