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Study of coherence tomography based on optical frequency comb

基于光学频率梳的相干层析成像研究

基本信息

批准号：
16360027
负责人：
KUROKAWA Takashi
金额：
$ 9.79万
依托单位：
Tokyo University of Agriculture and Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2005
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-16360027/
关键词：
OCT octical freauencv comb interferometer FRM 段差計測ファラデー回転鏡

项目摘要

A range of techniques, including coherence scanning microscopy, three-dimensional sensing by coherence radar, and scanning white-light interferometry, have been developed for simultaneous measurement of the three-dimensional step height of discontinuous objects and tomographic imaging. These techniques, however, require mechanical scanning with a piezoelectric transducer or a precision translator. Spectral interferometry, on the other hand, potentially offers a powerful means for high-speed absolute threedimensional shape measurement of objects without moving mechanical parts. The practical applicability of such methods, however, remains limited due to the high cost of tunable lasers with sufficiently wide range (e.g., external cavity laser diodes and dye lasers) and the slow speed of data acquisition because of the large number of calculations in the Fourier transform. As an alternative interferometry-based approach, synthesis of the coherence functions has been reported to be suitable for distance measurements. This method involves pseudo-frequency comb generation by frequency modulation of a laser diode. Yet this method is not suitable for surface profilometry because the frequency-comb interval is limited to the order of megahertz.In this Letter, a novel frequency comb-based interferometry technique for profilometry and tomography is proposed. The optical frequency comb employed by this method can be adjusted simply, allowing interferometry to be performed at frequency intervals of up to gigahertz order. The method is therefore suitable for measurement of absolute distances of several micrometers to several meters without the need for mechanical movement.Step-height measurement with 9 μm accuracy was successfully performed by sweeping the comb interval frequency. Thickness measurement of a glass plate was also demonstrated. This profilometry method is expected to be useful for both surface profilometry and tomography.

一系列的技术，包括相干扫描显微镜，三维感测相干雷达，扫描白光干涉，已被开发用于同时测量的三维台阶高度的不连续的物体和断层成像。然而，这些技术需要用压电换能器或精密转换器进行机械扫描。另一方面，光谱干涉法可能提供了一个强大的手段，高速绝对三维形状测量的对象没有移动的机械部件。然而，由于具有足够宽范围的可调谐激光器的高成本（例如，外腔激光二极管和染料激光器）以及由于傅立叶变换中的大量计算而导致的数据采集速度慢。作为一种替代的基于干涉的方法，相干函数的合成已被报道适合于距离测量。该方法涉及通过激光二极管的频率调制产生伪频率梳。然而，这种方法是不适合的表面轮廓术，因为频率梳间隔被限制在兆赫的顺序。在这封信中，提出了一种新的基于频率梳干涉轮廓术和层析成像技术。这种方法所采用的光频梳可以简单地调整，允许在高达千兆赫量级的频率间隔上进行干涉测量。该方法适用于测量几微米到几米的绝对距离，不需要机械运动，通过扫描梳齿间隔频率成功地实现了9 μm精度的步高测量。还演示了玻璃板的厚度测量。这种轮廓术方法预计是有用的表面轮廓术和层析成像。