【作者】 胡晓军；

【导师】 李圣怡；

【作者基本信息】 国防科学技术大学 ， 机械工程， 2008， 博士

【摘要】 在详查卫星、天文望远镜和激光核聚变等光学领域快速发展的带动下,现代光学系统对大型光学镜面的需求与日俱增。大型光学镜面对于实现光学系统的高精度、高分辨率以及高功率有至关重要的作用。而大型光学镜面因其口径大、精度要求高且需求量逐步增加对现代光学制造和检测技术提出了较大的挑战。现代光学制造的精度和效率很大程度上取决于检测技术。大型镜面光学加工需要高精度、高分辨率以及定量化可在位的检测技术支持。而现有的传统测量方法在很多方面还不能满足大型镜面加工的需求,成为制约光学生产能力进一步提高的瓶颈。为寻求新的技术解决途径,本论文研究了基于相位恢复技术的光学镜面检测方法,为大型光学镜面的加工提供新的定量化在位检测支持,以达到提高光学镜面的加工效率的目的。相位恢复技术是一种根据光场强度来反推相位分布的方法。相位恢复技术作为一种测量技术应用于镜面测量具有结构简单,对在位环境适应能力强,适于定量计算分析等特点。因而有着良好的应用前景,可以成为非常有效的大型镜面在位检测方法。论文的研究工作包括以下几个部分:1.在现有典型相位恢复原理基础上,构建基于离焦光场的相位恢复镜面测量系统。结合研究了离焦光场相位恢复测量的原理,给出适用于离焦光场检测系统的精确快速波面衍射计算方法。结合约束集投影理论,在GS迭代算法的基础上设计了多离焦图像的相位恢复迭代算法,并从几何意义上分析了算法的收敛性。2.对相位恢复测量系统的灵敏度做了分析,建立多平面灵敏度分析方法。得到了相位恢复测量灵敏度的一些基本性质,如距离焦点较近的图像的灵敏度较高以及收敛误差随灵敏度的提高而下降等,为测量参数的设计提供了理论依据。另外,根据实际测量系统性能,进行了误差分析以及可靠性和量程范围分析。分析表明现有测量系统的测量精度和量程范围能够满足加工对在位测量的精度要求。分析表明,相位恢复测量系统的精度较高,能够满足在位测量的需要。衍射图像的明暗分布与面形误差的高低分布之间有明显的对应关系。利用此性质可以直接判断误差的方向和位置,估计误差的幅度。3.针对大型镜面对高分辨率测量的需求,提出了亚像素相位恢复方法。构建了亚像素相位恢复的算法原理,并进行了仿真和测量实验。根据实际测量条件分析了图像噪声和图像离轴对亚像素相位恢复的影响。研究结果表明亚像素相位恢复算法能够有效地提高测量分辨率,具有很强的可实现性,给镜面的高分辨率测量提供了新的方法。同时也给其它领域的高分辨率相位恢复测量提供了新的思路。4.提出了实现非球面镜无补偿镜测量的相位恢复测量方法,使用球面波光源对非球面镜进行相位恢复测量。分析了非球面镜在球面波测试光照射下的光场衍射汇聚特性。研究了由非球面度造成的光场“自干涉”的性质和变化规律以及对测量造成的影响。提出了采用遮光和调节光源位置方法来实行非球面相位恢复测量规划以降低测量的非球面度。在非球面测量规划和常规相位恢复算法的基础上,构建了专门的并行非球面相位恢复测量算法。为了提高方法的实用性,还研究了提高计算效率的等效波长近似算法。从实验角度出发对光源和衍射图像的定位问题进行了研究。并分析了定位误差对测量结果的影响,讨论了镜面遮光误差对测量的影响和控制方法。5.为验证方法的有效性,进行了大量的实验研究。包括200mm和500mm口径的球面镜检测实验、250mm口径的球面镜亚像素测量实验以及对175mm口径的抛物面镜检测实验。实验全部在模拟在位条件下进行。分别对各个实验的测量现象和结果进行了分析。总体上,相位恢复测量结果与干涉测量一致,测量误差的大小与误差分析相吻合,测量精度能够满足数控加工的要求。实验表明环境对测量无明显影响,说明相位恢复测量能够适应在位测量环境条件。更多还原

【Abstract】 The requirement for large optical mirrors has grown rapidly under the background of many applications such as space detailed survey cameras, laser fusion systems and astronomical telescopes. Large optical mirrors are of special importance to the performance of high accuracy, high resolution and high power in modern optical system. Modern technology meets serious challenge in the manufacture and measurement of these large optical mirrors for their ever-increasing aperture, accuracy and amount.The accuracy and efficiency of optics manufacture depends heavily on the optical measurement technology. The process of large optics manufacturing needs the supporting of on-sit quantitative testing with high accuracy and high resolution. But traditional testing methods cannot meet the requirement of large optics manufacture in many aspects, that has turn out to be a bottleneck to further improving the ability of modern optics manufacture.For exploring a new way of optical measurement, this thesis studies an optical testing method based on phase retrieval, which can serve as a new quantitative on-site testing method to enhance the efficiency of optics manufacture. Phase retrieval is a wavefront sensing method that utilizes intensities to reconstruct the phase of optical field. As an optics testing method, phase retrieval has the advantages of simplicity, adapting to the on-site environments and suiting for quantitative calculation. So phase retrieval has a good application foreground and will be a very effective testing method.The content of this thesis is organized as follows:1. The phase retrieval testing system based on the defocus wave field has been designed according to the theory of classical phase retrieval. The fast computation method for wavefront diffraction is presented which is necessary in phase retrieval algorithm. The multi-images phase retrieval algorithm is established based on GS algorithm under the theory of projections to constrain sets. The geographic analysis is performed about the converging of this algorithm.2. The sensitivity of the phase retrieval system is studied, and the model that calculates the sensitivity of the multi-planes phase retrieval system is established. Some basic properties of phase retrieval sensitivity are derived. It can be proved that the images close to the focus have higher sensitivity and the phase retrieval error can be reduced with the sensitivity enhanced. The error analysis and reliability analysis with measurement range evaluation are also preformed in details. The error analysis indicates that the accuracy of phase retrieval system can meet the requirement of on-sit testing. The reliability analysis reveals that the bright and dim distribution of images has direct relationship with the high and low distribution of mirror surface shape, which can be utilized as a visualized method to estimate the mirror surface shape.3. The sub-pixel phase retrieval algorithm has been invented to meet the demand of high resolution testing for large mirrors. The principle of sub-pixel phase retrieval has been established, and some numerical experiments are carried out. The influence of noise and off-axis of images to sub-pixel phase retrieval has been studied. The results of sub-pixel study show that this method can significantly improve the testing resolution and brings a new way to high resolution testing. The sub-pixel method as a general idea can also give contribution to other application of phase retrieval where the high resolution testing is needed.4. The phase retrieval method that tests aspheric mirror without auxiliary optics has been invented, which tests aspheric mirror using spherical testing beam. The focusing characters of aspheric mirror under the illumination of spherical testing beam have been studied. The phenomena of“self-interference”together with its influence to the phase retrieval testing have been analyzed. To reduce the“self-interference”due to the aspheric surface, the optimization method has been presented by adjusting the position of point source and shading a part of mirror aperture. A special parallel aspheric phase retrieval algorithm has been designed for aspheric testing and is suit for multi-processors computation. To enhance the compution efficiency of aspheric phase retrieval algorithm, the approximate algorithm using equivalent wavelength has been designed. The location problem of point source and images are studied.The influence of the location error to the measurement accuracy has been estimated for experimental consideration. The mirror shading, which is used to reduce the“self-interference”, has been discussed including the mirror shading error and error controlling method.5. To validate the effectiveness of phase retrieval method, many experiments have been conducted including 200mm and 500mm spherical mirrors testing, 250mm spherical mirror testing with sub-pixel method and 175mm parabolic mirror testing. These experiments are performed under the on-sit surroundings. The experimental phenomenon and results are analyzed. The results of phase retrieval kept high compatibility with interference testing. The accuracy of phase retrieval can meet the requirement of computer controlling manufacture. The testing error agrees with the estimation of error analysis.The experiments also show that the influence of surroundings is insignificant and the phase retrieval has good adaptability for on-sit testing.更多还原