| 题名 | 频域光学相干层析成像系统的研制 |
| 作者 | 丁超 |
| 学位类别 | 硕士 |
| 答辩日期 | 2009 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 王向朝 |
| 关键词 | 光学相干层析成像 频域OCT 光谱校准 色散补偿 Lomb周期图 |
| 其他题名 | Research and Development of a Fourier Domain Optical Coherence Tomography System |
| 中文摘要 | 光学相干层析成像技术（Optical Coherence Tomography, OCT）是一种基于低相干光干涉术的非侵入高分辨层析成像技术，在活体生物组织成像、亚表面无损检测等领域具有广泛的应用前景。频域OCT相对于时域OCT技术在成像速度和灵敏度方面有较大优势，是OCT技术的发展方向。本论文针对频域OCT系统研制中的关键技术问题开展研究，建立了一套频域OCT实验系统，为频域OCT技术的深入研究和实用化奠定基础。本论文工作主要包括： 1. 介绍了频域OCT技术的原理，分析了频域OCT系统的分辨率、信噪比等性能参数。在此基础上，对系统光源、干涉仪以及光谱仪的设计进行了详细地阐述。 2. 针对光谱仪设计过程中遇到的光谱校准问题，提出了一种基于干涉谱迭代比较的光谱校准方法。该方法有效地提高了系统的信噪比和纵向分辨率，而且不需要使用额外的波长标定光源，降低了系统的复杂性。 3. 阐述了系统的软件控制和数据处理流程，着重分析了色散和插值方法对于系统纵向分辨率和信噪比等性能参数的影响。针对高分辨率OCT系统中的色散问题，提出了基于空间滤波的深度分辨色散补偿方法。计算机仿真模拟结果表明：该方法可以对样品不同深度的色散采用不同的色散系数进行优化补偿，从而达到最佳补偿效果。 4. 基于研制的频域OCT系统，对牛奶中的玻璃片、鱼眼眼前节等多组样品进行了成像实验，获得了清晰的样品断层图像。测试了纵向分辨率、横向分辨率和信噪比等系统参数。实验结果表明，系统在1.5 mm深度范围以内达到了20μm的纵向分辨率和70 dB的信噪比，横向分辨率约为20μm。 5. 针对现有频域OCT系统在数据处理过程中引入插值误差，导致系统信噪比下降的问题，提出了基于Lomb 周期图变换的频域OCT图像重建方法。基于该方法直接对 域非均匀采样的干涉谱变换得到空域的A-line信号，避免了插值过程，提高了系统的信噪比。 |
| 英文摘要 | Optical coherence tomography (OCT) is a promising optical imaging technique based on low coherence interferometry. OCT has the advantages of noninvasive detection, high imaging speed and high resolution. Fourier domain OCT (FDOCT) has attracted intensive researches recently because it has higher speed and higher sensitivity than time domain OCT (TDOCT). A FDOCT system is researched and developed. Key issues including dispersion compensation and spectral calibration are studied. The dissertation focuses on the following contents: i. The principle of FDOCT is introduced. System characteristics, including axial resolution, lateral resolution, imaging depth and SNR, are studied. The issues of light source selection, interferometer design and CCD grating spectrometer design for the development of the FDOCT system are discussed. ii. A new spectral calibration method based on iterated mapping of spectral interferograms is proposed to calibrate the home-made spectrometer. No extra calibration light source is required in this method as compared to traditional methods. Experimental results show that the spectrometer is calibrated accurately by using this method, which improves the SNR and axial resolution of the system. iii. The system control software is developed and data processing is analyzed. The influences of dispersion and interpolation on SNR and axial resolution are studied. To solve the problem of dispersion, a depth resolved dispersion compensation method is proposed. Simulation results show that the dispersion in different layers is compensated accurately with different dispersion coefficients by this method. iv. System parameters including axial resolution, lateral resolution and SNR are studied experimentally. The results show that in the depth range of 1.5 mm, the axial resolution and SNR are 20μm and 70 dB, respectively. The lateral resolution is about 20μm. Cross-sectional images of several kinds of samples, including glass plate in milk and anterior segment of fish eyes, are obtained by the FDOCT system. v. A new method based on Lomb periodogram (LP) transform to generate FD-OCT images is proposed. With this method, the signal in z domain is generated directly from the unevenly sampled spectra in k domain and no interpolation is necessary. As Lomb periodogram transform is insensitive to noises, it achieves higher SNR than traditional resampling and iFFT method. The proposed method is verified by simulations and experiments. |
| 语种 | 中文 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/16404]  |
| 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 | 丁超. 频域光学相干层析成像系统的研制[D]. 中国科学院上海光学精密机械研究所. 2009. |
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