【作者】 王朝阳；

【导师】 戴福隆；

【作者基本信息】 清华大学 ， 固体力学， 1999， 博士

【摘要】 细微观力学的发展迫切要求建立微米、亚微米尺度上的实验力学方法。本文提出并实现了在测量灵敏度、空间分辨率等方面均满足细微观力学实验测量要求的微米云纹方法以及相关的超高频精确制栅与条纹图像的数字化分析处理技术。 本文对激光干涉法制作全息光栅的高衍射效率、超高频精确制栅技术进行了分析和研究。(1)提出了利用光栅的衍射性质来精确确定两束相干光相交角度的思路,实现了基于标准母栅的精确倍频制栅方法。(2)本文在精确倍频制栅和常规折射率介质传光制栅方法的基础上,提出了基于母栅的折射率介质传光精确倍频制栅方法,所制得的光栅频率等于空气中制栅光路的制栅频率与两倍母栅频率之和,而与激光波长以及介质的折射率无直接关系。本文对该方法进行了详细的理论分析并将其思路推广于云纹干涉法,提高了测量的灵敏度。(3)本文从理论上分析建立了采用正性光致抗蚀剂进行光刻制栅的刻槽模型,得到了决定光栅刻槽深度与衍射效率的几个主要因素;此外还提出了一种全息光栅的复制新技术。本文所制作和复制的光栅均达到了非常高的水平。 本文将显微放大的思路应用于云纹法,提出了具有高灵敏度和高分辨率的微米云纹法。其原理是利用显微系统将高频光栅放大至能够形成几何云纹的低频水平,而其灵敏度仍取决于原始的高频光栅,空间分辨率的提高则由显微系统提供。分析比较与实验的结果均表明,微米云纹法可以满足细微观力学测量对高灵敏度和高分辨率的双重要求,均能达到微米、亚微米的水平,是填补微米——纳米层次实验力学方法空白的有效手段。实现微米云纹法的关键是如何提高条纹质量,本文提出了采用4F光学空间滤波等相应的解决措施。 本文全面地、系统地研究了光测条纹图像数字化自动处理的条纹中心分析技术和位相分析技术。(1)在条纹中心分析技术的图像滤波、条纹中心提取与修整、条纹级数赋值与插值、处理结果显示等多方面提出了一系列实用有效的处理方法。其中在关键的图像滤波和条纹级数插值方面,本文分别提更多还原

【Abstract】 Development of micro-mechanics requires experimental methods of high sensitivity and high spatial resolution, which should both reach or exceed micron-level. In this dissertation, a high sensitivity, high spatial resolution micron moire method and its correlative techniques of ultrahigh frequency grating fabrication and digital image processing are presented.Techniques of fabricating high diffraction efficiency and ultrahigh frequency gratings by interference of coherent lights are studied. (1) The diffraction property of gratings is adopted to adjust the angle of the two coherent lights, and a grating-fabrication method with multiplying-frequency is realized. (2) Based on multiplying-frequency and conventional refractive index medium grating-fabrication methods, a multiplying-frequency grating-fabrication method using high refractive index medium is proposed. The advantage of this method is that the grating’s frequency has no direct relation with the wavelength of the laser and the refractive index of the medium, but equals the grating-fabrication frequency in the air plus twi-frequency of the mother grating. Theoretical analysis of this grating-fabrication method is discussed in detail and the idea is also applied to enhance the sensitivity of moire interferometry. (3) A theoretical model of grating grooves fabricated with positive photo-resist is established, and several factors that affect the grating’s diffraction efficiency are gained. Furthermore, a new grating-replication technique is proposed. The gratings fabricated and replicated in the dissertation all have high diffraction efficiencies.Based on classical geometric moire method and microscopic principle, a high spatial resolution and high sensitivity geometric micron-moire method is presented. With a microscopic moire system, the high frequency gratings could be magnified to a low frequency level, so geometric micron-moire patterns can be formed. The sensitivity of micron moire method is determined by the high frequency of original gratings, while the resolution is determined by themagnification of the microscopic system. Experiments show that both the spatial resolution and the sensitivity can reach or exceed micron-level. Compared with other grating-based photo-mechanics methods, micron moire method could provide whole-field moire patterns of both high spatial resolution and high sensitivity. Additionally, some measures are used to enhance the contrast of microscopic moire patterns effectively, e.g., a 4F optical filter system.Fringe center technique and phase analysis technique, the two most important digital processing techniques for automatic fringe patterns analysis, are studied thoroughly. (1) A series of methods are presented in image filtering, fringe center detection, fringe order determination and interpolation, results display, and so on. Especially, a neighborhood-average filtering method with altering-windows is proposed to pre-process the fringe patterns, and a subsection-curve interpolation algorithm is used to ensure the derivative of the fringe order to be continuous. (2) Based on the characteristic of fringe edges, some effective modifications to conventional median-filtering method are proposed. The most important step of phase analysis processing is phase unwrapping, so a bi-directional linear scanning method is proposed. This method can avoid propagating errors, which always exists in traditional path-dependent methods. Furthermore, a tile Cellular Automata phase unwrapping algorithm, a promising path-independent method, is studied.An interface-advanced, powerful and effective software-system of automatic fringe patterns analysis using digital processing techniques is established. The software includes both fringe center technique and phase analysis technique.更多还原