光學同調斷層掃描（Optical Coherence Tomography）是相當具有潛力的光學造影技術。其應用低同調干涉儀的原理並以麥克森干涉儀作為系統的基本架構，此系統可對未知樣品進行非侵入的內部結構成像。由於其具有非侵入性與高解析度的優點，因此其廣泛用於生醫領域與工業領域上。
頻域光學同調斷層掃描技術（FD-OCT）相對於時域光學同調斷層掃描技術，具有較高的採樣速率跟解析度的優點。但在傳統的頻域光學同調斷層掃中，光譜儀所接收到的頻譜訊號需要經過反傅立葉轉換，然而在轉換過程中，自相干涉項的產生導致樣品的干涉訊號不易被區分，而鏡像的產生導致量測範圍受限制。因此消除不必要的訊號成了當前的主要工作。
在本論文中，我們提出了一個改良的頻域光學同調斷層掃描系統架構，可以同時獲得兩組相位移的正交極化光，利用相位移演算法消除不必要的訊號達到兩倍的量測範圍，並且改良光路上的設計，使我們可以同時量測出未知樣品的厚度及折射率。換句話說，這提出的改良頻域頻域光學同調斷層掃描可以一次性且全域的同時量測光學樣品的厚度與折射率。

Optical coherence tomography (OCT) is a potential technique of optical imaging. It utilized the principle of low coherence interferometry (LCI) and based on the structure of Michelson interferometer. The OCT system can provide internal structure of unknown sample with non-invasive imaging. Because optical coherence tomography has the advantages of non-invasive and high-resolution, it is applied in biomedical and industrial fields.
Compare to the TD-OCT, the FD-OCT has the advantage of higher sampling speed and resolution. The OSA detect the spectrum of interference signal, the spectrum of interference signal need to be transform by the inverse Fourier transformation (IFFT). In the conversion process, the generated autocorrelation terms and symmetry mirror image result in the interference signals of the sample no easy to be distinguished and the measurement range is restricted. Thus eliminating the noise term became present main job.
In this study, we propose an improved FD-OCT structure that can simultaneously obtain the two phase-shifting signals from two orthogonally polarized lights. By phase-shifting algorithms over orthogonally polarized light, eliminating those unnecessary noise terms and doubling the measurement range. By designing the optical path, we can simultaneously measure the refractive index and the thickness of unknown sample by FD-OCT. In other words, this improve structure of FD-OCT achieve simultaneous measurement of thickness and refractive index of optical samples based on full-range and one-shot measure.

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