全范围测量复谱频域OCT系统

为了提高复杂多层样品的测量范围,构建了复谱频域光学相干层析成像系统．通过重建图像的振幅和相位可以减小图像的噪声,提高图像的质量,并对样品进行了实验．实验结果表明,该系统可以消除谱频域OCT图像中的寄生项和镜像,改善和提高层析图像质量,有效测量范围提高了2倍,实现了全量程的有效探测．     

采用频域快速延迟线的光学相干层析系统的研制

建立了一套单模光纤型光学相干层析(OCT)成像系统。系统采用了不同于国内其他组的新型频域快速扫描延迟线(FD-ODL)和外差平衡接受技术,采取了一系列提高系统信噪比的方法,成功地实现高信噪比(113dB)、高分辨率、大成像深度的层析图像的提取,获得了纵向分辨率9μm、横向分辨率10μm、深度2.88μm的清晰的皮肤OCT图像。该系统比传统的采用时域延迟线的OCT在信噪比上高出了一个量级。     

快速高分辨率的频谱光学相干层析成像系统研究

光学相干层析成像（OCT）是一种用于生物组织成像的新型技术.该技术在非接触及无创成像方面的分辨率可达到微米量级.目前,大多数的OCT系统主要为时域OCT,为获取深度图像,需要对参考臂的光程进行长度扫描,采集速度受到了限制.为此研制了一套频谱OCT系统,由于该系统避免了参考扫描,故可实现极高的采集速度（1 000线/s）,使实时成像成为可能;分析了频谱OCT的理论探测深度（6.26 mm）和分辨率（13μm）;应用该系统对50μm厚的塑料薄膜进行了成像,实验证明实际分辨率高于50 μm.     

基于成像光谱仪的频域OCT的实验研究

针对传统点扫描OCT系统的成像速度对OCT在实际研究和应用中的影响,本文提出并搭建了一种高速无扫描频域OCT系统,对该系统的成像分辨率、探测深度与各种噪声进行分析,并提出一种新的消除背景噪声的方法.该系统根据频域OCT和成像光谱仪的基本原理和工作特性,采用一种新的干涉光路以线聚焦方式对样品进行高速数据采集.实验结果表明,这种系统无需任何扫描装置就可得到二维层析图像,在对载玻片8 mm宽度范围成像时,其速度比传统点扫描方式快两个数量级;利用文中提出的数据处理方法成功将背景噪声消除.     

线聚焦光学相干层析术的研究

提出了一种高速光学相干层析(OCT)成像技术方案。利用柱面镜的成像特性将传统OCT的点聚焦成像模式改变为线聚焦成像模式,从而降低二维OCT图像的扫描维数,达到提高成像速度的目的。利用ZEMAX光学软件对系统进行光线追迹获得光束经过柱面镜后的聚焦情况。随后采用635nm的激光光源和柱面镜构建了实验系统,实验结果很好地验证了光线追迹仿真结果。     

光学相干层析技术在眼科手术导航方面的研究进展

在眼科显微手术中,传统的术中成像方式由于缺少深度信息,限制了内部结构和手术器械的可视化。光学相干层析成像技术(OCT)是一种非接触式断层成像技术,由于其能提供深度信息、非侵入、成像快、分辨率高等优点,被广泛应用于眼科手术的术中导航。典型的OCT设备可分为手持OCT和显微镜集成OCT。本文简要介绍了时域OCT和频域OCT的原理和发展,回顾了OCT眼科手术导航设备的发展历程,并对各个类别中有代表性的OCT系统进行了介绍,对其成像原理、性能、优缺点等进行了描述和对比,最后对该技术在眼科手术中的应用做出了总结和展望。     

光学相干层析术系统性能分析——时域和频域OCT

对时域和频域光学相干层析术(Optical coherence tomography,OCT)系统的性能通过理论计算,进行分析和比较,对时域和频域OCT系统的特性进行深入的研究,为OCT系统的性能分析和提升提供理论依据。     

眼科光学相干层析成像设备分辨率关键参数的小型化检测装置研制

通过分析眼科光学相干层析设备的成像分辨率理论计算模型,设计并研制了一套用于测量其光源光谱和系统数值孔径的小型化检测装置。针对一台商业化的临床在用眼科光学相干层析设备,通过对其关键参数的测量,得到该设备的纵向分辨率为6.9μm,横向分辨率为42.3μm。该检测装置未来可作为眼科光学相干层析设备的质控与计量器具。     

组织精细结构的光学高分辨数据获取与图像重建

光学弱相干层析成像(OCT)技术可以对生物组织高分辨率无损成像。依据获得的样品光学截面数据,再通过三维重建,可以得到生物组织精细结构的再现。在生物组织结构再现的研究中,对于目前常用的生物组织切削照相、X-ray、超声这些方法,OCT作为一种无损高分辨率的3D光学显微技术是一种很好的补充。     

基于数字希尔伯特变换的OCT信号处理与系统实现

信号处理方法的选择是光学相干层析(OpticalCoherenceTomography,OCT)系统研制的重要环节,直接决定着OCT系统的硬件构建和实现。应用硬件实现OCT信号处理的方法虽然速度快,但存在硬件开销大,系统配置可调节性差等缺点。进而采用了基于数字希尔伯特变换的软件方法来处理OCT信号。该数字处理方法对探测得到的离散干涉实信号进行解析拓展,得到同时具有振幅信息和相位信息的复信号,其中的振幅信息被用于OCT的图像重建。介绍了研制的光纤OCT系统和各驱动单元的同步时序控制,最后给出了人体皮肤和洋葱的OCT高清晰层析图。     

Resolution improvement with dispersion manipulation and a retrieval algorithm in optical coherence tomography

We propose and demonstrate what is to our knowledge a novel technique of improving the spatial resolution of an optical coherence tomography (OCT) system given a non-Gaussian light source spectrum. By using dispersive materials in the reference arm of the OCT system, the resultant dispersion variation led to a full-width at half maximum (FWHM) of the interference fringe envelope smaller than the Fourier transform-limited value of a Gaussian spectral shape with the same spectral FWHM, at the expense of significant tails. The effects of the tails, which would blur the OCT images, were tremendously reduced with a retrieval algorithm. Simulation results and processed OCT scanning images have shown the capability of the proposed technique.     

Image enhancement for multilayer information retrieval by using full-field optical coherence tomography

When a full-field optical coherence tomography (OCT) system is used to extract tomographic images from a multilayer information carrier, the resulting images may suffer from interlayer modulations and parasitic patterns derived from interference fringes. We describe and analyze these negative influences that degrade the quality of extracted tomographic images and propose practical algorithms and methods to minimize them. The emphasis of the discussion will be the removal of the parasitic fringes produced by the imperfection of a CCD camera. The simulative and experimental results of image enhancement for multilayer tomography extraction using full-field OCT are provided.     

Digital algorithm for dispersion correction in optical coherence tomography for homogeneous and stratified media

The resolution of optical coherence tomography (OCT) often suffers from blurring caused by material dispersion. We present a numerical algorithm for computationally correcting the effect of material dispersion on OCT reflectance data for homogeneous and stratified media. This is experimentally demonstrated by correcting the image of a polydimethyl siloxane microfludic structure and of glass slides. The algorithm can be implemented using the fast Fourier transform. With broad spectral bandwidths and highly dispersive media or thick objects, dispersion correction becomes increasingly important.     

Dispersion compensation in high-speed optical coherence tomography by acousto-optic modulation

We report studies of the analyses of and compensation for group dispersion to improve the axial resolution of high-speed optical coherence tomography (OCT) by acousto-optic modulation (AOM). Theoretical modeling and experiments reveal that the high-order group dispersion induced by acousto-optic crystals broadens the measured coherence length (Lc) and thus degrades the axial resolution of OCT imaging. Based on our experimental studies, we can compensate for the dispersion to less than 50% broadening of the source Lc by adjusting the grating-lens-based optical delay in the reference arm and can further eliminate it by inserting like acousto-optic crystals in the sample arm of the OCT system. The results demonstrate that this AOM-mediated OCT system permits high-performance OCT imaging at A-scan rates of as much as 4 kHz by use of a resonant scanner. Because of its ultrastable direct frequency modulation, this AOM-mediated OCT system can potentially improve the performance of high-speed Doppler OCT techniques.     

Noise analysis of a combined optical coherence tomograph and a confocal scanning ophthalmoscope

A fiberized optical coherence tomographic (OCT) system is modified to produce a confocal image similar to that produced by a scanning laser ophthalmoscope. Two possible configurations are presented, one that can deliver either an OCT or a confocal image and another that is capable of producing both the OCT and the confocal images simultaneously. Using the later configuration, we demonstrate such images from the retina in the living eye. The penalty in terms of performance reduction introduced into the optical coherence tomograph when integrated with a confocal receiver and the signal-to-noise ratio analysis for the different confocal receiver configurations are presented.     

Fundamental characteristics of a synthesized light source for optical coherence tomography

We describe the fundamental characteristics of a synthesized light source (SLS) consisting of two low-coherence light sources to enhance the spatial resolution for optical coherence tomography (OCT). The axial resolution of OCT is given by half the coherence length of the light source. We fabricated a SLS with a coherence length of 2.3 microm and a side-lobe intensity of 45% with an intensity ratio of LED1:LED2 = 1:0.5 by combining two light sources, LED1, with a central wavelength of 691 nm and a spectral bandwidth of 99 nm, and LED2, with a central wavelength of 882 nm and a spectral bandwidth of 76 nm. The coherence length of 2.3 microm was 56% of the shorter coherence length in the two LEDs, which indicates that the axial resolution is 1.2 microm. The lateral resolution was measured at less than 4.4 microm by use of the phase-shift method and with a test pattern as a sample. The measured rough surfaces of a coin are illustrated and discussed.     

Enhancement of intrinsic optical signal recording with split spectrum optical coherence tomography

Functional optical coherence tomography (OCT) of stimulus-evoked intrinsic optical signal (IOS) promises to be a new methodology for high-resolution mapping of retinal neural dysfunctions. However, its practical applications for non-invasive examination of retinal function have been hindered by the low signal-to-noise ratio (SNR) and small magnitude of IOSs. Split spectrum amplitude-decorrelation has been demonstrated to improve the image quality of OCT angiography. In this study, we exploited split spectrum strategy to improve the sensitivity of IOS recording. The full OCT spectrum was split into multiple spectral bands and IOSs from each sub-band were calculated separately and then combined to generate a single IOS image sequence. The algorithm was tested on in vivo images of frog retinas. It significantly improved both IOS magnitude and SNR, which are essential for practical applications of functional IOS imaging.     

Lensed fiber probes designed as an alternative to bulk probes in optical coherence tomography

We demonstrate a compact all-fiber sampling probe for an optical coherence tomography (OCT) system. By forming a focusing lens directly on the tip of an optical fiber, a compact sampling probe could be implemented. To simultaneously achieve a sufficiently long working distance and a good lateral resolution, we employed a large-mode area photonic crystal fiber (PCF) and a coreless silica fiber (CSF) of the same diameters. A working distance of up to 1270 microm, a 3 dB distance range of 2210 microm, and a transverse resolution of 14.2 microm were achieved with the implemented PCF lensed fiber; these values are comparable to those obtainable with a conventional objective lens having an NA of 0.25 (10 x). The performance of the OCT system equipped with the proposed PCF lensed fiber is presented by showing the OCT images of a rat finger as a biological sample and a pearl as an in-depth sample.