【作者】 郎治国；

【导师】 谭久彬；

【作者基本信息】 哈尔滨工业大学 ， 仪器科学与技术， 2010， 博士

【摘要】 随着光学加工和检测技术的不断发展,大口径范围深度非球面光学元件已成为天文光学、空间光学和地基空间目标探测与识别、激光大气传输、惯性约束聚变(ICF)等领域中起支撑作用的关键部件之一。制约大口径非球面镜加工水平的关键,则取决于与制造要求相适应的检测方法和仪器。对于传统的接触式测量法,其致命缺陷是易于划伤光学元件的表面;而非接触式测量法中,全口径干涉法和子孔径拼接干涉法也因补偿透镜制作困难和拼接过程易产生误差累积等因素的影响而无法满足大口径范围深度非球面镜的加工需求,因此,开发和研制一种高精度、非接触式的大口径非球面测量系统势在必行。课题“基于超精密回转扫描的大口径非球面测量技术研究”的目的是在基于f-θ透镜系统的大型非球面测量技术基础之上,探讨研究一种高精度、非接触式的近平面大口径非球面三维轮廓回转扫描测量技术,以二维位相板生成的衍射准直光束为测量基准光束,并以衍射光斑的暗线为位移基准,用超精密直线气浮导轨实现扫描光束的精确定位,大口径非球面镜的回转运动由超精密气浮转台实现。本课题为解决大口径近平面非球面三维轮廓测量技术中的高精度和非接触问题开拓了一种有效的技术途径,并为研究真正意义上的大口径范围深度非球面测量技术提供了有力的理论依据和先期的准备工作。本课题的研究,在大型同步辐射用非球面镜、柱面镜以及细长型光学表面的三维轮廓测量中也有广泛的应用前景。本文首先从衍射型长程轮廓仪(LTP)的工作机理入手,分析了基于衍射准直技术的f-θ透镜系统的基本特征,并结合测量装置的实际结构,分析了影响系统斜度测量精度的各因素,为将衍射型LTP进一步拓展到大口径非球面测量技术中奠定了坚实的理论基础。为实现大口径非球面的三维轮廓检测,提出了一种基于超精密回转扫描的大口径非球面测量系统。该系统通过将超精密直线运动和超精密回转运动有机合成,以实现被测表面的回转扫描测量,充分利用了回转基准运动精度高的技术优势,可大大减小由运动机构引入的斜度测量误差。针对三维轮廓测量要求,提出了一种二维斜度光学扫描头结构。该扫描头包含两个可分别对径向及切向斜度进行测量的子扫描头,并能够对测点处的二维斜度信息进行同步采集,两个子扫描头中的误差补偿光路均能够实时、动态补偿由激光束角漂引起的斜度测量误差,进而有效减小由激光束角漂引起的三维轮廓测量误差。结合基于超精密回转扫描的大口径非球面测量系统的结构组成,以矩阵光学和向量形式的折、反射定律为理论基础,分析了各误差因素对二维斜度测量的影响机理,并进一步对各误差因素的权重进行了比较,从而为系统研制过程中各部件的加工和选型提供了可靠的理论依据。为了减小衍射光斑的平滑过程引入的斜度测量误差,研究了一种曲线窗口旋滤波方法,并将滤波效果与传统滤波方法进行了比较,分析结果表明:曲线窗口旋滤波方法在有效滤除图像噪声的同时,能够较好地保持衍射光斑暗线区域的光强分布特征,进而减小测量及参考光斑的亚像素定位误差。同时,为了选择高精度的数值重构方法,提出了一种对不同数值方法在频域内进行比较的评定方法,进而为选择重构精度高、噪声抑制能力强的数值方法提供了理论依据,有利于轮廓测量精度的提高。最后,根据预研目标,研制了基于超精密回转扫描的大口径非球面测量系统样机,并对样机进行了实验测试。实验中选择了直径为50mm的平面镜作为被测对象,并将样机的测量结果与国际上轮廓测量水平较高的AK100菲索干涉仪进行比对,比对结果为:PV值=0.1λ,RMS值=0.05λ,从而验证了基于超精密回转扫描的大口径非球面测量方案的可行性。更多还原

【Abstract】 With continuous development of optical fabrication and measurement technology, the large aperture deep aspheric optical component has been one of the key parts which make important role in following regions: astronomical optics, space optics, detection and identification of foundation space target, atmospheric transmission of laser, inertial confinement fusion etc.. The key factor that confines machining level of large aperture aspheric is decided by measurement method and instrument which are adaptive to machining requirements. For traditional contact measuring method, the fatal flaw is its easy damaging surface of optical elements. Among non-contact measuring methods, both whole aperture interference and sub-aperture stitching interference methods can not meet machining requirements of large aperture aspherics because of difficult fabrication of compensating lens and error accumulation in process of stitching. Therefore, it is necessary to develop a kind of high precise and non-contact measuring system of large aperture aspherics.The subject“Study on Technique of measuring large aperture aspheric surface based on ultra-precise rotary scanning”is to develop a high precise and non-contact three dimensional profile rotary scanning measuring technique of hither plane large aspheric surface which is based on measuring technique of large aspheric surface based on f-θlens system. The diffractive collimated beam generated by two-dimensional phase plate is used as measuring basis beam and dark line of diffractive spot is looked as location basis. The precise location of scanning beam is realized by ultra-precise linear air floating rail and the rotary motion of large aperture aspherics is realized by ultra-precise air floating turntable. The subject develops a effective technique for solving three-dimensional profile measurement of hither plane large aperture aspheric surface and provides theoretical basis and preparation work for developing measurement technique of large aperture deep aspheric surface. The application of this technique in measuring synchrotron radiation aspherics, cylindrical surface, thin and long optical surface is prospective.According to operation principle of diffractive long trace profiler (LTP), the basic characters of f-θlens system based on diffractive collimated technique are analyzed. Considering factual structure of measuring equipment, every factor affecting measuring accuracy of slope is also analyzed. Therefore, the firm theoretical basis for introducing diffractive LTP to measuring technique of large aperture aspheric surface is built.In order to measuring three-dimensional profile of large aperture aspheric surface, a kind of measuring technique of large aperture aspheric surface based on ultra-precise rotary scanning is presented. The rotary scanning measuring of surface under test is realized by combining ultra-precise linear motion and ultra-precise rotary motion, then measuring error of slope caused by motive structure is greatly reduced because of high precise rotary base motion.Aiming at measuring requirement of three-dimensional profile, a kind of two-dimensional slope optical scanning head is presented. It consists of two sub scanning heads which respectively measure slopes along radial and tangential directions, furthermore, the two-dimensional slope of measured spot can be detected simultaneously. The error compensation optical paths in the two sub scanning heads can real-time and dynamically compensate slope error caused by angle shift of laser beam, then the three-dimensional profile measuring error caused by angle shift of laser beam can also be reduced greatly.Considering structure of measuring system of large aperture aspheric surface based on ultra-precise rotary scanning, the effects of every error factor on measuring two-dimensional slope are analyzed based on matrix optics and law of refraction and reflection in vector form. In addition, weights of every error factor are also compared, then theoretical basis for machining and selecting of every part in process of development is provided.In order to reduce measuring error of slope caused by filtering diffractive spot, a filtering method based on curve window is studied and compared with traditional filtering methods. The analyzing results show that the filtering method based on curve window can effectively filter image noise without changing distribution of optical intensity around dark line of diffractive spot, so sub-pixel location error of measurement and reference spots may be reduced greatly. At the same time, in order to select high precise numeric reconstructing method, an assessment method which compares different numerical reconstructing methods in frequency domain is presented, which provides theoretical basis for selecting high precise and strong ability of suppressing noise numerical reconstruction method. Furthermore, measuring accuracy of profile is improved.At last, according to research target, the prototype of large aperture aspheric surface measurement system based on ultra-precise rotary scanning is developed and is tested experimentally. The flat mirror whose diameter is 50mm is used as measured object, and the measuring result is compared with AK100 fizeau interferometer whose measuring level is higher in the world. The experimental results show that PV value and RMS value between the two kinds of method are respectively 0.1λand 0.05λ, and then the measuring method of large aperture aspheric surface based on ultra-precise rotary scanning is demonstrated to be feasible.更多还原