光學同調斷層掃描攝影術之色散研究

The Investigation of Dispersion Effect in Optical Coherence Tomography

劉哲豪(Zhe-Hao Liu)

指導教授 ： 鄭旭志

國立虎尾科技大學/電機資訊學院/光電與材料科技研究所/碩士(2014年)

https://doi.org/10.6827/NFU.2014.00026

摘要

光學同調斷層掃描(OCT) 是一種高分辨率、非接觸、非破壞性的生物醫學成像新方法。通過高分辨率，探測樣品不同深度層面背向反射回來的光強度，可以得到樣品的深度資訊。此技術是以低同調干涉原理為基礎，麥克森干涉儀為架構。目前，提高分辨率的主要方法是使用頻寬更寬的低同調光源。然而在實際測量系統中，樣品的色散效應也會隨著光譜寬度的增加而變得嚴重，在色散介質中，由於色散相位因子的影響，使得干涉信號會隨著樣品深度拓寬，在包絡拓寬的情況下OCT信號幅度會降低、信噪比下降，影響OCT的最終成像。此外，在色散介質中對薄層結構進行成像，還會出現干涉信號分裂的情況。因此OCT 系統的色散補償研究，是必須且重要的主題。
本論文對OCT系統的色散問題作了比較全面的理論分析和實驗研究。在理論方面介紹了光源的同調性問題，和增加頻寬提高深度分辨率時有關的色散損失，以及研究包絡拓寬的主因與關係式。在實驗方面基於現有的光源，以玻璃為樣本量測不同深度所造成的包絡拓寬情形。並利用參考臂加入補償介質法進行色散補償的實驗，最後提出另一套色散補償架構使用啁啾光纖光柵對OCT系統的干涉訊號進行整波實驗。

關鍵字

光學同調斷層掃描 ； 低同調干涉技術 ； 色散 ； 色散係數 ； 色散補償

並列摘要

Optical coherence tomography (OCT) is an optical biomedical tissue-imaging technique with a high-resolution, non-contact, and non-destructive optical sensing technology. OCT uses back-reflected infrared light from different layers in depth through high-resolution to obtain the depth of the sample. OCT utilizes a low-coherence light and the Michelson interferometer. Currently, the way to improve high resolution is mainly to use an interferometer with a low coherence, broad bandwidth light source. However, in the actual measurement, dispersion of the sample becomes an essential issue with the increase of spectral bandwidth. In the dispersion medium, with a phase factor, the interference signal is influenced by the depth of the sample. In the case of signal envelope broadening, the signal amplitude of OCT decreases, signal-to-noise ratio (S/N) decreases; as a result, it may influence the final image. Therefore, the study of dispersion compensation in OCT is worth discussing.

In the study, the researcher explored both the theoretical and experimental studies on the issue of dispersion compensation in OCT. As for the theories, the researcher discussed optical coherence, dispersion and losses when increasing resolution in depth, and the causes and relationships toward envelope broadening. For the experimental design, based on the current light source, the researcher took glass as the sample to measure envelope broadening in different depths. Besides, the researcher also adopted the reference mirror to add the dispersion medium to conduct the experiment of dispersion compensation. Finally, the researcher proposed a dispersion compensator utilizing Chirped Fiber Bragg Grating (CFBG) to process wave shaping for the interference signal in OCT.

並列關鍵字

Optical coherence tomography ； low-coherence interferometry ； Dispersion ； Dispersion Compensation

參考文獻

[19] 周祐仲,2008,”利用光學同調斷層掃描儀測量液體中不同濃度以及溫度造成折射率的變化”,國立清華大學生醫工程與環境科學系碩士論文.

[20] 許明軒,2011,“使用正交極化光於全域式頻率域光學同調斷層掃描之研究與實驗驗證”,國立虎尾科技大學光電與材料科技研究所碩士論文.

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