結合超寬頻光源以提供光譜解析度的共軛焦雷射掃描眼底鏡

Abstract

視網膜是一個由掌管視覺影像的神經所組成之脆弱的層狀組織。現代科學家藉由非侵入式顯微術如共軛焦雷射掃描眼底鏡，即可得到視網膜的資訊，同時藉由此唯一的窗口進行不傷害身體的血管健康觀測。共軛焦雷射掃描眼底鏡能提供視網膜的三維結構，對於視網膜病變的診斷有很大的用處。由於疾病往往伴隨化學成分的改變，具光譜解析度的雷射掃描眼底鏡可以藉由樣品的光譜變化而早期發現疾病。此外因為視網膜上的神經細胞對於光線的波長極為敏感，具光譜解析度的眼底鏡能藉由不同波長的光激發視神經，讓神經科學有更大的想像空間。 過去曾經有人嘗試將光譜影像能力與雷射掃描眼底鏡結合以在活體中進行視覺的色彩研究。然而這些研究都受到了雷射光源以及系統的像差影響。我們提出一套結合超寬頻光源的雷射掃描眼底鏡。藉由光子晶體光纖內的非線性效應，我們可以將單一波長的紅外光雷射換成頻寬由可見光到紅外光的光源。此外我們也以面鏡架設了一套具有繞射極限性能的雷射掃描眼底鏡，以克服一般透鏡系統的色像差。這套系統讓我們能以非侵入式的方法取得活體視網膜的光譜影像，同時簡化以往同類型實驗的步驟。另外這樣的系統也讓我們可以自由選擇光的波長以用來激發視神經，並且觀察神經的訊號傳遞。

Retina is a fragile layered tissue composed of neurons responsible for color vision. It is not only part of central nervous system (CNS) which can be investigate noninvasively, but also the only window that microscopic inspection of circulation system can be taken without invasion. A confocal scanning laser ophthalmoscope (cSLO) provides three-dimensional structure of retina, which is important to retinopathy diagnosis. As diseases usually occur with biomedical change of tissue, a spectrally resolved cSLO can diagnose the illness in the early stages by analyzing absorption spectrum of the tissue. Furthermore, because the neurons on retina are sensitive to the wavelength of the light exposed to, a spectrally resolved cSLO facilitates the studies of the neuroscience about retina. There have been several attempts of spectrally resolved cSLO, but the performances of those systems were all limited by the bandwidth of the lasers and the chromatic/geometric aberration of optics. Here a spectrally resolved cSLO with bandwidth from visible to infrared is demonstrated. The broadband light source is a supercontinuum laser, which is generated from the nonlinear effects in a photonic crystal fiber. We also construct a mirror-based scanning system with diffraction-limited performance, overcoming the aberration problems in previous multispectral systems. With this system, spectral images of living retina from visible to infrared are acquired in a noninvasive manner. Resolution is around 3µm in living zebrafish, which is adequate for cone cell recognition and researches about retina, vision and neuroscience.