OCT轴向超分辨研究

【作者】 周琳；

【导师】 丁志华；

【作者基本信息】 浙江大学 ， 光学工程， 2006， 硕士

【摘要】 光学相干层析成像术(Optical Coherence Tomography,OCT)是一种将低相干迈克尔逊干涉仪和共焦扫描显微术相结合的极具潜力的新型光学成像方法。其轴向分辨率由光源带宽和探测光束的聚焦条件共同决定。目前用来提高OCT轴向分辨率的方法主要基于带宽光源技术。本文提出一种将光学超分辨术与OCT相干门有机结合的方法来提高OCT的轴向分辨率。通过适当形式的光瞳滤波器,使OCT系统轴向响应的主瓣宽度缩小到相干门之内,而其旁瓣则处于相干门之外,不对相干成像产生有效贡献。这样能够在光源带宽不变的条件下,有效提高OCT的轴向分辨率,避免了采用宽带光源所带来的费用昂贵和系统复杂等缺陷。 本文从三维点扩散函数理论出发,针对OCT的结构特点,结合OCT轴向超分辨要求对几种典型的振幅型光瞳滤波器和位相型光瞳滤波器做了详细的数值分析和讨论。最后在OCT系统平台上进行了轴向超分辨初步实验研究。 本文正文部分共分为五章。第一章概述了光学超分辨研究技术的发展趋势。介绍了OCT相关原理,总结了当前提高OCT轴向分辨率的各种方法,阐述了利用超分辨术改善OCT轴向分辨率的种种优势。第二章是光学超分辨理论基础,对焦点附近点扩散函数的性质进行了详尽分析。结合不同光瞳滤波器的特点讨论了评价光学超分辨效果的影响因子。第三章仔细考察了OCT的轴向超分辨要求,按照这个标准对振幅光瞳滤波器和位相型光瞳滤波器作了详细的理论推导,得出了两种适用于OCT轴向超分辨的理论方案。第四章将理论方案与实际的OCT系统相结合,采用三区位相型光瞳滤波器进行了OCT轴向超分辨实验研究,并分析了影响超分辨效果的各种因素。第五章对课题作出总结并提出了今后需要努力的方向。更多还原

【Abstract】 Optical coherence tomography (OCT) is an emerging modality which combines confocal scanning microscopy and low coherence interference technology. Axial resolution in optical coherence tomography (OCT) imaging is determined by the coherence length of light source and the beam-focusing condition. Currently, the most adopted approach for achieving high axial resolution in OCT is using a light source with a broaden bandwidth. In this thesis we propose an alternative method to increase the axial resolution of OCT by combining coherence gating with superresolution through an appropriate phase filter. In the proposed OCT system, the width of the central lobe of the axial point spread function is narrowed within the coherence gate of the light source, while its side-lobes are lying outside without contributing to coherence imaging. It is in this way that we can obtain improved resolution in OCT system without recurring to broadening the bandwidth of light source, which is nevertheless costing and inconvenient in implementation.We start off with the theory of three dimensional point spread function, analyze superresolution characteristics of amplitude filters and phase filters based on the requirement of axial superresolution in OCT system, and carry out the experiment using an assigned filter on OCT system in laboratory.Four chapters are included in this thesis. In chapter 1, the development of superresolution and the principle of OCT are introduced. The most adopted approach to increase axial resolution of OCT system is summarized and several advantages of the application of axial superresolution in OCT are presented. In chapter 2, the characteristics of point spread function near the focus are analyzed in detail based on the theory of superresolution. Different kinds of optical filters are enumerated and three factors used to evaluate the effect of superresolution are discussed. In chapter 3, the axial gains of several classical optical filters are calculated according to the requirement of enhancement of axial resolution in OCT by superresolution. Two theoretic schemes are put forward in order to actualize the axial superresolution of OCT. In chapter 4, theoretical results and laboratorial OCT system are combinedthrough a three-zone phase filter in experiment. Various factors that influence the effects of superresolution are analyzed concretely. In chapter 5, the project is summed up and further assignments about the improvement of our scheme are suggested.更多还原