【作者】 雷湧；

【导师】 陈晓冬；

【作者基本信息】 天津大学 ， 光学工程， 2012， 硕士

【摘要】 OCT(Optical Coherence Tomography,光学相干层析技术)是一种基于白光干涉的光学成像技术,可以对生物组织内部微观结构进行横断面层析成像。OCT技术以其无损伤、非介入、分辨率高等优点,在科学研究和生物医学等领域具有广泛的应用前景。本文针对OCT中图像分辨率和清晰成像范围相互矛盾的缺点,深入分析光谱OCT系统的扫描模型和高斯光束自身的影响,借鉴合成孔径雷达(Synthetic Aperture Radar, SAR)的数据处理方法,在课题组近似波数域算法研究的基础上,利用合成孔径算法实现了图像重构,获得了分辨率一致的图像。论文主要完成了以下工作:1.详细分析了光谱OCT的基本成像原理和系统扫描模型,借鉴合成孔径雷达的数据处理方法,提出了用于横向扫描和旋转扫描的合成孔径算法来实现图像重构,提高了图像的分辨率。2.根据光谱OCT系统的横向扫描结构,研究了OCT的衍射物理模型,分析了高斯光束的宽度和波前对图像质量的影响,在此基础上推导出散射的前向模型和图像重构步骤,得到参考光、样品光以及干涉光谱数据的表达式。3.比较了SAR的距离多普勒(Range Doppler, RD)算法和波数域算法,提出了改进的RD算法,将光谱数据的二维处理分解成两个一维处理:利用波数域的变量替换进行横向距离徙动校正,利用匹配滤波器进行纵向压缩,分别提高了图像的横向和纵向分辨率。为了将OCT技术应用于内窥成像,提出了基于旋转扫描的合成孔径算法,改善了图像质量。4.针对影响图像质量的主要参数,利用MATLAB进行了横向扫描和旋转扫描的仿真模拟,并搭建光纤型光谱OCT系统,选取新鲜猪肝作为样品进行实验。实验结果与仿真结论相一致,由此验证了算法的正确性。更多还原

【Abstract】 Optical coherence tomography (OCT) is a latest optical imaging technology based on the white-light interferometry, which can acquire cross image for interior microscopic view of biological system. OCT has many advantages such as non-traumatic detection and high resolution, thus it possesses a wide prospect in scientific research and clinic application.In this paper, the scanning model of spectral domain optical coherence tomography (SDOCT) system and effects produced by Gaussian beam itself are discussed. Referring to the data processing methods of synthetic aperture radar (SAR) and the approximate wavenumber domain algorithm which our group has researched, we propose the synthetic aperture algorithm to abate the compromise between resolutions and depth of focus in SDOCT, and achieve image reconstruction with spatially invariant resolution.The researches mainly focus on the following aspects:1. The paper analyzes the fundamental principle and scanning model of SDOCT in detail. Referring to the data processing methods of SAR, the synthetic aperture algorithms for transverse scanning and rotary scanning respectively are proposed to implement image reconstruction with high resolution.2. According to the structure of transverse scanning, the physical model of diffraction is presented, along with the finite beam width and the shape of wavefronts produced by Gaussian beam taken into account. On the basis of scattering forward model, the equations of reference light, sample light and interference spectrum are deduced, as well as the procedure of image reconstruction.3. This paper compares the range Doppler (RD) algorithm and wavenumber domain algorithm. The improved RD algorithm is applied to improve the resolutions in the axial and lateral directions, where the two-dimensional processing of the spectrum data is decomposed into two one-dimensional processings of variable exchange and matched filter. The synthetic aperture algorithm is demonstrated to improve the image quality in the rotary scanning, which makes it possible that OCT can be used in the endoscopic system.4. The simulations are implemented in terms of the key parameters that influence the image quality. Properly selecting optical devices, the fibre-based interference system is built, and images of fresh pig liver are gained, which effectively shows that the algorithm will be competent for imaging.更多还原