基于光学相干层析术的组织光学性质测量

通过在光学相干层析成像(Optical Coherence Tomography,OCT)模型中考虑多重散射的影响,提出了一种提取出不同深度处的组织光学性质,包括散射系数和各向异性因子的算法.当把吸收系数作为算法中的第三个拟合参量时,能减少算法拟合过程中由于吸收作用的影响而带来的误差.基于包含吸收因子的OCT扩展模型,改进的算法也能够提取出吸收系数.这些算法的有效性通过对聚苯乙烯微球溶液样品的测量实验得到验证.     

透明剂对生物组织光学相干层析成像的影响研究

生物组织光透明技术针对生物组织具有的高散射及浑浊特性,严重影响生物组织成像的对比度及分辨率等问题,提供了较好的解决办法。把离体猪皮表面涂抹不同浓度的聚乙二醇、甘油、丙二醇这些光学透明剂(Optical Clearing Agents, OCA),利用光学相干断层析(Optical Coherence Tomography, OCT)技术对其进行动态监测,有效地提取测量信号在渗透过程中随测量深度的变化。结果表明,利用光透明技术均可增加OCT的成像深度,但对于不同OCA不同深度的作用效果不同。该研究为了解OCA浓度及作用时间对于不同深度最优选择,提供有价值的数据参考,进一步理解了OCA的作用机制,对于OCA在医学方面的应用有一定的指导作用。     

光学相干层析图像的处理研究

提出一种基于各向异性扩散算法Catté模型的图像处理改进方法,通过对阈值k的修改以控制扩散强度,可实现在平滑光学相干层析图像的同时保护图像的边缘特征.对不同样品的光学相干层析图像处理.实验结果表明,改进后的算法更有利于噪音的滤除和边缘特征信息的保护.     

Optical Coherence Tomography System based on Synthesis of Optica Coherence Function with a Wavelength-Scanning Laser Source

A new optical coherence tomography system using a wavelength-scanning laser source is presented. The system has the advantage that the depth resolution can be controlled by the scanning range. In general, rapid scanning of the wavelength varies the output power of the laser source, and it is difficult to detect a weak signal of reflected light from the scattering object. By synchronizing the intensity-integrated detector with the variation, the dynamic range of the detection has been improved. To confirm the performance, tomographic imaging of biological tissues is demonstrated.     

共路径光相干成像系统光纤探头的研究

本文提出了基于楔形光纤以及端面成角度光纤的共路径光相干成像系统探头,实现背向散射信号在其端部的共路径相位干涉,从而获得待测件断面成像信息.首先,建立了共路径光相干成像系统光路及探头相位干涉的理论模型,分析了各光纤探头尺寸与干涉信号强度、系统性能的关系.其次,分别设计出楔形光纤、端面成角光纤探头,开展了共路径光路干涉实验,搭建了工作波长为1 550 nm的共路径光路测试系统.然后,根据不同待测样品的散射率,设计并研制了不同角度的楔形光纤探头,分析了不同尺寸的光纤探头对系统性能的影响,针对不同样品开展了固定探头探测实验.实验结果表明,楔形光纤端部可直接对输出光聚焦,照射在被测样品上,且其端面成一定角度时,可调节输出分光比,实现对参考信号的调节,提高了系统信噪比.为进一步开展共路径光相干成像系统的研究奠定了基础.     

光学相干层析成像系统的实验研究

介绍了作者研究建立的光学相干层析（ＯＣＴ）成像系统,给出了利用该系统得以的实际生物样品光学相干层析图像,并对系统性能和结果作了分析,讨论了影响系统性能的一些因素及改进方法。     

光学相干层析成像色散补偿研究

针对通过增加光源谱宽度来提高光学相干层析成像系统分辨率时样品色散特性的限制作用,分析了色散与光学相干层析成像系统纵向光程分辨率的约束关系.根据物质色散特性,采用数值变换方法对光学相干层析成像相干成像信号进行了色散补偿.实验使用了中心波长1 550 nm 自激发辐射光源和光纤迈克尓逊干涉结构,对水和光学快速扫描延迟线引入的二阶和三阶色散进行了数值补偿并通过相位修正因子来改善补偿效果.确定了一种普适的、快速的数值色散补偿方法.在对水中盖玻片和生物组织和的光学相干层析成像图像的色散补偿实验中取得了良好的效果,证明了方法的可行性.     

Optical Coherence Tomography Premiere in Korea

Optical Coherence Tomography (OCT) is considered as fundamentally new image modality having advantages such as high-speed, real-time cross sectional imaging with non-invasive in vivo investigation of biological tissue and its potential for clinical application is highly evaluated. In spite of these merits, the research activity in OCT has not taken much attention until recently. However the situation in Korea is gradually changing due to understanding of its versatile applications. Active research and commercialization are underway. Bulk optics-based OCT system is changed into alignfree fiber-optics system. With our expertise in the fabrication of fiber grating devices and strong background in control of fiber based system, we hope to contribute in developing simplified all-fiber OCT system with better performance. As a leading research group, working on OCT, we have firstly implemented fiber-based OCT system in Korea and demonstrated the imaging performance with glass plate and onion.     

光学相干层析成像的实验研究

用光纤迈克耳孙干涉仪方法,建立了一种相干门层析成像实验装置,在此系统中,采用相干长度仅为２５ｕｍ的超辐射管作光源,测量了样品浸泡在牛奶乳浊液情况下的干涉信号。     

光学相干层析成像轴向超分辨研究

为了提高光学相干层析成像(OCT)的轴向分辨率,采用OCT与光学超分辨术相结合的方法,设计了三区相位型和振幅型两种光瞳滤波器,并将制作的光瞳滤波器应用于系统的样品臂中,分别测量不同条件下对应的轴向响应曲线,结果与理论分析基本吻合,实现了轴向分辨率10％以上的提高,从而验证了利用合适光瞳滤波器实现OCT轴向超分辨的可行性.     

光学相干层析成像色散补偿研究

针对通过增加光源谱宽度来提高光学相干层析成像系统分辨率时样品色散特性的限制作用,分析了色散与光学相干层析成像系统纵向光程分辨率的约束关系.根据物质色散特性,采用数值变换方法对光学相干层析成像相干成像信号进行了色散补偿.实验使用了中心波长1550nm自激发辐射光源和光纤迈克尓逊干涉结构,对水和光学快速扫描延迟线引入的二阶和三阶色散进行了数值补偿并通过相位修正因子来改善补偿效果.确定了一种普适的、快速的数值色散补偿方法.在对水中盖玻片和生物组织和的光学相干层析成像图像的色散补偿实验中取得了良好的效果,证明了方法的可行性.     

Monitoring of the Process of Immersion Optical Clearing of Collagen Bundles Using Optical Coherence Tomography

Optics and Spectroscopy - Future development of the method of immersion optical clearing of biological tissues—this method is widely used in the study of the morphology and pathologies of...     

光学相干层析成像的图像重建

层析成像技术－光学相干层析术是基于光学低相干反射测量发展而来的。介绍了用图像恢复的基本原理在光学相干层析术图像增强方面的工作。通过实验测量行到了解卷积所必需的点扩展函数。重建后的膜层结构图像的深度分辨率提高了一个数量级,图像也取得了了的锐化、去噪的效果。     

Novel Optical Delay Line for Optical Coherence Tomography System

A novel all-fiber optical delay line for an advanced optical coherence tomography (OCT) system is proposed. Using the distributed reflectance characteristic of a chirped fiber Bragg grating (CFBG), the optical delay can be obtained without leaving the fiber that forms the system. The proposed delay line consists of a pair of identical CFBGs. The gratings are cascaded in reverse order to cancel the inherent wavelength dependency of CFBGs. Tunable optical delay is obtained by applying small strain on one of the CFBGs through an attached piezo actuator. The small displacement induced by the piezo actuator is amplified by a factor of up to 100 due to the distributed reflectance characteristic of the CFBGs. This principle and characteristics of the proposed optical delay line are analyzed in detail.     

Range Technique in Scattering Medium Using a Needle-Fiber Optical Coherence Tomography System

A needle-fiber optical coherence tomography (OCT) system designed for guiding epidural anesthesia to a target is presented. In the preliminary experiment, a desired target in tofu as a strong scattering medium can be monitored over a sufficient range of several millimeters within a short measuring time. The axial resolution is 21 μm. In order to investigate the ranging performance, the relation between background noise levels and focus-scattering properties in a confocal optical system is numerically studied by use of Monte Carlo technique. Numerical results indicate that an appropriate focal length of the lens attached to the fiber should be used to separate the OCT signal from strong noise in strongly scattered medium.     

Non-Scanning Optical Coherence Tomography Using Off-Axis Interferometry with an Angular-Dispersion Imaging Scheme

We present a non-scanning approach for real-time optical coherence tomography (OCT). Our approach is based on an off-axis interferometer that laterally projects the time-of-flight or depth information of the sample onto an image sensor. To facilitate the use of an off-axis interferometer in OCT, an angular-dispersion imaging method has been developed. Theoretical analysis and experimental results are presented to demonstrate that this method is capable of demodulating the interferogram and thus permits a direct inspection of the depth-resolved image. Depth resolution and detection range of the present method are also studied.     

基于FPGA的快速全场光学相干层析方法

针对全场光学相干层析术实用化时成像速度不高的问题,提出一种基于FPGA控制的相位调制快速全场光学相干层析系统成像方法.首先用FPGA搭建电路以产生频率可调的高准确度正弦信号与脉冲信号,然后利用所产生的信号作为调制频率,采用四步移相法获取光学断层图像.采用该方法对洋葱表皮细胞进行光学断层成像,并与传统相移法及采用单片机调制方式获取的图像进行对比,结果表明该方法不仅能提高成像质量,且对高分辨率光学断层图像的采集时间从目前的4s(0.25 Hz)减少到0.03~0.05s(20Hz~35Hz),提高了系统的成像速度.     

光学相干层析系统相干传递函数研究

在弱物体近似下从成像系统角度对光学相干层析测量技术进行了理论研究。分析了该技术测量样品纵深结构时图像的形成机理。结果表明它相当于一复振幅线性平移不变系统，从而可用相干传递函数描述系统性能，所得相干传递函数表明系统具有低通特性，半峰值带宽△ｋ＝２△λ／λ＾２。由于物体频谱整体平移了１／λ，测量的是纵向结构的高频信息。本文的工作为定量分析光学相干层析对未知结构的测量结果及进一步提高空间分辨率提供了理论     

激光相干层析成像的光散射模拟计算

利用低相干光作为光源的光学相干层析技术是一种新型成像技术。本文利用蒙特－卡罗（Ｍｏｎｔｅ－Ｃａｒｌｏ）模拟计算方法研究了该技术在不同的散射条件下,相干调制信号随散射系数的变化关系,得出了单次散射和多次散射的差别以及它对成像质量的影响,并进一步讨论了利用单次散射和多次散射信号,提高光学相干层析术图像清晰度和信号强度的方法。还研究了光束半径大小对成像分辨率的影响及变化过程,得出了对实验有指导意义的结果     

视网膜光学相干层析图像的预处理方法

光相干层析技术(OCT)是近来发展起来的成像技术,利用光相干层析技术可以得到清晰的视网膜以及黄斑区的层析图。主要论述了在开发视网膜光相干层析图像识别和临床诊断系统中采用的图像预处理方法。利用图像分割、图像增强等处理技术,实现了图像的自动边缘检测与轮廓提取。通过对视网膜光相干层析图像进行预处理,为进一步的图像识别与分析打下了良好的基础。对黄斑囊样水肿、黄斑裂孔以及正常的视网膜光相干层析图像进行了实验,均取得了较好的效果。