【作者】 顾永刚；

【导师】 褚家如； 翟超；

【作者基本信息】 中国科学技术大学 ， 精密仪器及机械， 2010， 博士

【摘要】 “大天区面积多目标光纤光谱望远镜(Large Sky Area Mulit-object Fiber Spectroscopic Telescope, LAMOST)"是我国的一项重大科学工程项目,在其直径1.75米的焦面板上,布置有4000根光纤。LAMOST观测时,望远镜光学系统使天体目标成像在焦面上,然后光纤定位系统控制4000根光纤与这些天体的像对准而获取它们的光谱。由于存在控制、机械加工、安装、工作环境改变等引起的误差,如果光纤定位系统是开环控制,精度不易保证,因此为了修正这些误差,使LAMOST能够准确运转,必须要对光纤在焦面上的位置进行精密检测。LAMOST光纤位置检测有如下要求：大视场、多离散目标、高精度、快速、非接触,几乎囊括了所有的高检测标准。在常规的位置测量方法中,近景摄影测量最有可能全部符合这些要求,因此本文对近景摄影测量在光纤位置检测中的应用进行了详细研究。摄影测量有基于线阵CCD和面阵CCD的两种可选设备,针对各自优缺点,本文提出了多线阵CCD的扫描检测方案和面阵CCD像机的分区检测方案,并对这两种方案都从原理和方法上进行了细致的探讨。论文的主要内容包括：1.设计并研制了一套由3个线阵CCD组成的光纤位置试验检测系统,该系统检测静止光纤坐标的误差为±0.9μm(2σ),具有很好的稳定性。2.实现了线阵CCD试验检测系统对动态光纤的位置测量。对线阵CCD姿态标定、转换拼接和参数优化后,实验显示,该系统检测光纤之间距离的误差只有±5μm(2σ),具有较高的精度。但高检测精度需要复杂的标定和优化,该过程需要大范围高密度的标定光纤。3.建立了光斑定位算法(光重心法)的误差分析模型,结合实验研究,提出了一个最佳的检测条件,在该条件下,光重心法的精度达到0.04像素,并以光重心法的精度为依据确立检测子区域的大小。4.提出一种改进的光束法平差自标定方法,实现面阵CCD像机的在线高精度标定。实验结果显示,该标定方法只需要数量很少的控制点就能够获得与多控制点的传统标定方法相当的精度。本文对线阵CCD方案的研究结果是,该方案具有较高的理论检测精度,若要在LAMOST现场应用,不仅需要大范围高密度的标定光纤,而且对系统硬件的性能和精度都有很高要求,以目前技术手段难以实现。本文研究并解决了面阵CCD方案中的几个关键问题,保证了面阵CCD方案从实验室论证顺利移植到LAMOST现场应用。更多还原

【Abstract】 Large Sky Area Mulit-object Fiber Spectroscopic Telescope-LAMOST, with a 1.75m-diameter focal plate on which 4000 optical fibers are arranged, is one of major scientific projects in China. During the surveying process of LAMOST, the optical imaging system makes the astrometric objects be imaged in the focal plane, and the optical fiber positioning system controls the 4000 fibers to be aligned with these objects and obtain their spectrum. If the optical fiber positioning system works in open-loop control mode, it’s difficult to ensure the positioning accuracy because of the errors caused by control, machining, installation and changes of the work environments. In order to correct these errors and make the LAMOST run accurately, it is necessary to detect the position of optical fibers in the focal plane accurately.The detection of optical fibers’position in LAMOST has the following requirements:large field, multi-discrete targets, high accuracy, rapid and non-contact, including almost all high testing standards. In the conventional position detection methods, the close-range photogrammetry has the most possibility of meeting all these requirements, so the application of the close-range photogrammetry is studied detailedly in this paper.Photogrammetry has two optional imaging devices:linear CCD and area CCD. For their advantages and disadvantages, multi-linear CCD scanning detection method and area CCD camera district detection method is proposed in this paper, and their measuring principles and processes are discussed in detail.This paper’s main content includes:1. The experimental detection system, which is consisted of three linear CCD, is designed and developed. The accuracy of detecting the static optical fiber’s coordinates is±0.9μm (2σ) which shows the system has a good stability.2. The position detection of dynamic optical fiber by the linear CCD system is achieved. After attitude calibration of the linear CCD, conversion splicing and optimization of parameters, the experiment demonstrates that the error of detecting the distance between the optical fibers is only±5μm (2σ) which is a high accuracy. However, the high detection accuracy requires complex calibration and optimization with a wide range of high-density reference optical fibers.3. An error analysis model of the spot location algorithm (light centroid method) is established, and the best detection condition is suggestted combined with the corresponding experiments. Under this condition, the accuracy of light centroid method is 0.04 pixels which could be used to judge the size of detection sub-region.4. An improved bundle adjustment self-calibration method is proposed to realize the on-line high-precision calibration of area CCD camera. The results of experiment indicate that this calibration method needs only a few control points while the traditional calibration methods need much more control points to get the same accuracy.The study of this paper on linear CCD method shows that it has high theoretical detection accuracy. However, it will need a wide range of reference optical fibers and high requirements on the performance and precision of hardware if the linear CCD method is applied on LAMOST in practice, and it’s difficult to realize with current technology.Some key problems of area CCD method are researched and solved in this paper, so the area CCD camera district detection method can be smoothly transplanted to the locale of LAMOST from the laboratory.更多还原