超高解析度頻域光學同調斷層掃瞄術－使用混合有機溶液

Abstract

利用有機發光二極體材料的技術發展衍生出低成本及高量子效率的顯示器已經成為了未來的趨勢。在這個研究中，使用了有機發光二極體的螢光材料當作基底並展示了一個簡單的光源應用於超高解析度頻域光學同調斷層掃瞄儀，由445nm半導體雷射當激發源激發兩種不同頻段混合的有機材料。在空氣中軸向解析度最高可達到1.7μm。 光學同調斷層掃瞄術（Optical Coherence Tomography, OCT），它本質上是一種低同調干涉儀，使部分透明樣品作二維或三維的非侵入式掃瞄。在時域OCT（TD-OCT）系統，以獲取深度信息（A-Scan）中，參考臂的長度必須被機械式地改變，這限制了其成像速度。近年來，由於先進的傅立葉域OCT（FD-OCT），包括掃頻源OCT（SS-OCT）和頻域OCT（SD-OCT）的廣泛使用，對於成像速度有了很大的提升，因為在參考臂中除去機械掃瞄儀，故能以每秒數百幀的速度掃瞄。在SS-OCT系統中，基於MEMS的掃頻源或傅立葉域鎖模雷射可以提供更多的A-Scan速率(超過100千赫)，在OCT掃瞄中產生的運動偽影將大大降低。目前商用掃瞄的CCD可以達到線速100千赫，等於SD-OCT系統的A-Scan速度。因此，無論是SS-OCT或SD-OCT系統都能夠提供比TD-OCT更快的成像速度。 在OCT的解析度中，透過公式(於2-3介紹)可得知解析度(resolution)正比於1/∆λ，其中∆λ為光源的半高寬(Full width at half maximum, FWHM)，所以我們利用把不同波段的有機染料(Organic dyes)染料混合、激發出寬頻的光源提供給OCT當作光源。 將兩兩接近的低波段和高波段的有機溶液混合，激發出比原來更寬頻的光源是本研究主要的賣點，而有機溶液混合有以下優點：1. 低成本、2. 容易製作、3. ∆λ可藉由不同波段的溶液混合來增加。

Technological developments of organic-LED (OLED) materials have ushered in the new era in display with low costs and high quantum efficiencies. In this work, the potential use of LED phosphors has been evaluated and demonstrated as a simple light source for ultrahigh-resolution spectral-domain optical coherence tomography (SD-OCT). Excited by a 445 nm diode laser, broadband spontaneous emission from three LED phosphors were generated in the visible regime. The best axial resolution was 1.7μm in air and corresponding 3D ultrahigh resolution SD-OCT imaging was performed with the proposed simple and broadband light source. Optical coherence tomography (OCT), which is inherently a low-coherence interferometer, enables three-dimensional (3D) noninvasive biopsy of partially transparent samples. For future OCT applications, the imaging acquisition speed and resolution are two key issues. The imaging speed is determined by the scanning mechanism. In a time-domain OCT (TD-OCT) system, to acquire a depth profile (A-scan), the length of the reference arm has to be mechanically changed, which limits the imaging speed. Recently, advanced by Fourier-domain OCT (FD-OCT) including swept-source OCT (SS-OCT) and spectral-domain OCT (SD-OCT), the imaging speed has been greatly improved to hundreds of frames per second by the removal of mechanical scanners in the reference arm. Furthermore, FD-OCT shows superior imaging speed and system sensitivity than those of TD-OCT systems. In SSOCT systems, a MEMS-based swept source or a Fourier domain mode-locked laser can provide an A-scan rate of more than 100 kHz, enabling motion artifacts during OCT scanning to be greatly reduced. In contrast, the imaging speed of SD-OCT system is determined by a high-speed line-scan CCD, which is employed as a detection mechanism. Currently, commercial line-scan CCDs can achieve a line rate of ~100 kHz, equal to the A-scan rate of the SDOCT system.