简介

傅立叶频域相干成像术（FD-OCT）通过分析麦克尔逊干涉仪中的干涉模式得到微米精度的表面横截面图象（如图1）。FD-OCT系统可以直接测量样品轴向的散射光强度，一次曝光就完全得出样品表面到内部的散射分布，这种测量通常被称为“A扫描”。一系列的A扫描组合得到横截面图象，该过程称为“B扫描”。相邻的横截面（B扫描）可重组成三维图象。高散射生物样品，典型的扫描深度是1mm到几个mm，这取决于样品的性质。

FD-OCT比早期的时域OCT系统（TD-OCT）敏感，这种敏感程度显著提高了数据采集速度和成像质量。目前，Thorlabs提供的频谱OCT系统，可达每秒8帧的速率，这样，可以实现临床、外科、工业和材料科学上的实时成像。更高的帧率，可以参见扫描光源OCT系统。

频谱OCT是一套完整的成像系统，无特殊要求，安装方便。这套系统包括手持探针、OCT主机、计算机、显示器和集成软件包，软件提供了控制硬件和图象处理的良好的图形界面。该系统由德国Lübeck医疗激光中心、Lübeck大学和Thorlabs美国及德国实验室工程师协作完成。

频谱OCT简单工作原理

图1（如下）描述了Thorlabs OCP930SR频谱OCT主机和探针的基本设计。宽带超发射二极管光源（SLD）的输出导入到手持式麦克尔逊干涉仪探针中，光束被分为两路，参考臂一端是反射镜，而另一路包括成像透镜将光聚焦到样品上，此成像透镜也被用来收集样品背向散射和反射光。两路光返回后再合成，直接进入光谱仪，其干涉模式经过分析得到频谱OCT图象。如果样品臂长度固定，干涉模式将是简单的波长的正弦函数形式，傅立叶变换后呈单一的峰。但是，由于样品中不同深度的背向散射和反射光影响，在正弦干涉模式上将存在幅度的调制。因为幅度调制于深度相关，经傅立叶变换可得到随深度变化的背向或反射光强度变化（即A扫描）。

Spectral Radar OCT Imaging System

Thorlabs Spectral Radar Optical Coherence Tomography (SROCT) Imaging System

Thorabls' Spectral Radar Optical Coherence Tomography (SROCT) systems are based on Fourier (frequency) domain technology which provides micron-level imaging of turbid media.  FD-OCT is a frequency-domain technique which offers several advantages over time-domain techniques due to the higher sensitivity that enables a significant increase in speed while maintaining high image quality. The resultant speed enhancement allows for rapid cross-sectional image collection, enabling facile imaging of larger sample volumes in real-time.  The Spectral Radar OCT is ideal for real-time imaging in clinical, surgical, industrial and material science applications.  Please visit our new Image Gallery for up-to-date application information including Human Cochlear Imaging and Ventilated Mouse Lung Imaging

This system was developed in collaboration with Thorlabs (USA), and three German-based organizations: Thorlabs Lübeck AG , Medical Laser Center Lübeck, and the University of Lübeck. This system combines a broadband light source with a high-speed spectrometer to perform Fourier domain detection of the OCT interference fringe signals.

System Description

Thorlabs’ Spectral Radar OCT Systems include a broadband super-luminescent diode (SLD) located in the base unit, which is fiber coupled to a Michelson interferometer. The interference signal, from the sample and reference arm reflections, is coupled back into the same fiber and is redirected by the fiber optic coupler to a high-speed spectrometer. The spectrometer uses a high-speed linear sensor array and supports a spectral resolution of 0.140nm. The analog and digital timing circuitry and all drive electronics are integrated in the base unit which is isolated both optically and electronically to ensure stable performance of the high-speed spectrometer. The analog interference fringe signal from the spectrometer is digitized by the data acquisition card installed in the computer, and the integrated software package provides complete control of measurement, data acquisition, and processing.  The system can be installed and operational within minutes.

The Spectral Radar OCT System is now available with two imaging options: a microscope design (upon request) or the standard handheld probe. Both systems have an integrated CCD camera and provide high resolution 2D imaging. In addition, the microscope version also provides 3D imaging capabilities

Standard Handheld Probe Version (OCP939SR)

• Integrated Michelson Interferometer in Probe Minimizes Mode Dispersion
• Telecentric Optics Provide Constant Illumination Spot Size Over a Broad Range of Working Distances
• 2D OCT Images up to 8 frames/second
• Real-time In-situ Imaging of Biological and Industrial Samples

Our OCP930SR imaging system includes:

• OCT Base Unit with Spectrometer
• PC, Monitor and Imaging Software
• Handheld Probe with Interferometer

Microscope Version (Available Upon Request)

 Thorlabs’ Spectral Radar OCT now offers a microscope version for 3D imaging capability. The microscope includes X- and Y- scanning mirrors for 2D scanning of sample surfaces. When combined with the depth profiling capability of OCT, 3D structures of the sample can be measured with high resolution in minutes. The microscope also has a built-in CCD camera to provide surface viewing of the sample which is convenient for real-time imaging of the samples.

• X- and Y- scanning mirrors
• 2D, depth profiling and 3D imaging
• Stage provides 2D sample translation (X, Y) and rotation

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