光学相干层析成像技术的研究及应用
文献类型：学位论文
| 作者 | 宋桂菊 |
| 学位类别 | 博士 |
| 答辩日期 | 2001 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 方祖捷 |
| 关键词 | Monte Carlo模拟方法 光学相干层析成像 白光干涉仪 波长扫描干涉仪 |
| 中文摘要 | 光在散射介质中传输受到介质的吸收和散射，改变了光的初始信息，如偏振、方向性、相干性等。因而对散射介质成像的关键问题在于提取掩埋在散射或吸收介质中与物体有关的信息，并获得高对比度、高分辨率及尽可能多的信息。光学相干层析成像(OCT)是对散射介质成像的有效技术之一。本文对光在多层介质中传输的Monte Carlo模拟方法进行了阐述。并且用它模拟了有限厚度双层混浊介质的反射光流量密度和反射光流量。研究了介质散射系数、吸收系数、单次散射各项异性因子和折射率对OCT成像对比度所起的作用。本文介绍了我们研制的一套OCT系统，并给出它对牛奶溶液中的物体、藕切片及鸡小肠的OCT成像的结果。对藕样品的一维纵深方向扫描的实验数据，进行Wiener滤波解卷积运算，消除光源的平滑作用。为了提高OCT技术在成像位置确定时的分辨率，本文采用了三种方法：对干涉信号进行曲线拟合。由于对干涉信号数据采样的不连续，干涉信号峰值位置，也就是相应散射位置的确定将存在一定的误差，将曲线拟合方法应用在峰值位置的确定上，可以有效地提高系统分辨率和测量重复率；采用信号处理方法使干涉信号强度重新分布。由于系统噪声的存在，干涉信号中心零级条纹的强度与相邻一级条纹的强度差很小以至于很难分辨，本文对干涉信号的数学处理可以提高分辨率；另外由两个或多个低相干光源构成的组合光源的使用也可以有效地提高一级和次级干涉条纹的强度差，从而提高系统在位置测量时的分辨率。采用白光光源替代宽带超辐射激光二极管作为OCT系统的光源，可以有效地提高成像的空间分辨率，同时获得样品光学参数的波长特性。本文模拟了分别以相对窄带光源和白光作光源时的OCT系统的干涉信号，并以具有彩色层状结构的散射介质为样品，模拟散射系数及吸收系数的波长特性。折射率分布对理解光在介质中的传输和医学诊断非常重要，本文描述了用OCT系统同时测量折射率和厚度的方法。并提出了使用波长扫描干涉仪无需任何扫描实现高分辨率三维成像并同时测量折射率和厚度的技术。它具有结构简单，信号处理方便的特点。组织光学这一领域还有许多理论和实用技术有待于进一步深入研究，随着这些技术的发展，混浊介质光学必将在人们的生产生活中得到广泛的应用。 |
| 英文摘要 | Photons are scattered and absorbed when they propagate in the scattering medium, which alter their initial characteristics such as polarization, direction, coherence and so on. Thus the key problem in imaging of scattering medium is how to extract the information regarding a certain object that is embedded in scattering and absorbing medium with high resolution, high visibility and more information. Optical coherence tomography (OCT) is one of the valid techniques for image of scattering medium. Monte Carlo method that simulated light propagation in multi-layered media was described in the dissertation. The photon flux and the density of reflected light propagating in finite two-layered media was modeled. The effects of scattering coefficient, absorbing coefficient, anisotropy and refractive index on OCT imaging contrast were studied. OCT system designed by us was described. The OCT images of object embedded in milk resolution, lotus root and cork intestine were obtained. For one-dimensional longitudinal scanning data of lotus sample the smoothing effect was eliminated through Wiener filter. For enhancing the resolution of OCT system in file determination of scattering position, three methods were adjusted. One is curve fitting. There are deviations in the determination of the peak position of interference signal or scattering position due to the non-continuity in signal sampled. During the process of determination of the peak position the curve fitting made the system resolution and measurement repeatability be increased greatly. Another one is signal processing to redistribute the interference signal intensity. Due to the existence of system noise, the difference between zero-order and the first-order peak of the interference signal is so small that their differentiation is difficult. A signal processing method that can increase the system resolution was proposed in this dissertation. Additionally, the use of combination source including two- or multi- wavelengths also increased the intensity difference between zero-order and the first-order peak of the interference signal, and then enhanced the system resolution in position determination. The variation of optical parameters with wavelength was measured by using white light source instead of SLD as the source of OCT system, and the resolution was enhanced temporarily. Taking a color layered scattering media as sample, we simulated white light OCT technique. The interference signal was obtained with narrow spectrum source and white light source, and the variation of scattering and absorbency coefficients with wavelength were also obtained through simulation. The detailed knowledge of the refractive index distribution is important to understand light propagation in medium and medical diagnosis. In this dissertation a method using OCT system to realize simultaneous measurement of the refractive index and thickness was proposed. And the method using wavelength-scanning interferometer (WSI) to realize three-dimensional image and simultaneous measurement of the refractive index and thickness without any scanning was presented. It had the feature of simple structure and easy signal processing. In tissue optics, further theoretical and experimental study is needed in this area. With the development of this technique, the scattering medium optics will be used widely. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15345]  |
| 专题 | 上海光学精密机械研究所_学位论文 |
| 推荐引用方式 GB/T 7714 | 宋桂菊. 光学相干层析成像技术的研究及应用[D]. 中国科学院上海光学精密机械研究所. 2001. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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