本文選題：微納光纖　切入點(diǎn)：微納光纖光柵　出處：《暨南大學(xué)》2014年博士論文

【摘要】：生物醫(yī)學(xué)工程是一門運(yùn)用自然科學(xué)和工程技術(shù)的原理與方法,研究各種生物體特別是人體的結(jié)構(gòu)、功能以及其它生命現(xiàn)象的科學(xué)。生物醫(yī)學(xué)成像技術(shù)是生物醫(yī)學(xué)工程領(lǐng)域最重要的組成部分之一,通過采用光學(xué)顯微、磁共振等物理手段,獲取人體組織內(nèi)部的空間光學(xué)吸收分布函數(shù),提取人眼無法獲取的有用信息,為疾病的早期診斷提供重要依據(jù),對人類健康具有重要意義。其中,光聲成像方法是基于光聲效應(yīng)、以超聲信號檢測為物理手段的新型成像方法,它結(jié)合了光學(xué)成像的高對比度優(yōu)勢和超聲成像的高穿透深度特性,成為當(dāng)今生物醫(yī)學(xué)工程研究領(lǐng)域的熱點(diǎn)。如何實(shí)現(xiàn)具有高探測精度、高對比度、高空間分辨率的光聲成像手段成為該領(lǐng)域研究人員的共同目標(biāo)。超聲信號檢測是光聲成像技術(shù)中的關(guān)鍵技術(shù)環(huán)節(jié),傳統(tǒng)采用壓電式傳感器進(jìn)行超聲信號探測,其靈敏度相對較低,響應(yīng)帶寬窄,不利于實(shí)現(xiàn)高性能成像。與之相比,光纖超聲傳感器具有較高的探測靈敏度,以及抗電磁干擾的特性。為了實(shí)現(xiàn)高靈敏度、高對比度和高空間分辨率的光聲成像方法,我們提出采用微納光纖光柵Fabry-Perot干涉儀進(jìn)行超聲信號探測。與傳統(tǒng)光纖超聲傳感器相比,這一器件是在直徑僅為幾個(gè)微米的光纖上制作的,具有更高的空間分辨率和更好的成像對比度特性。同時(shí),借助微納光纖的強(qiáng)瞬逝場作用和高反射率的光纖光柵刻寫技術(shù),對超聲信號的響應(yīng)靈敏度也顯著提升。本文的主要內(nèi)容包括:微納光纖光柵Fabry-Perot干涉儀是進(jìn)行光聲成像的物理基礎(chǔ),本文首先對其制備工藝、光譜特性和傳感特性進(jìn)行了研究。該器件是采用193nm準(zhǔn)分子激光器在微納光纖上依次刻寫兩根光柵而制成的。采用多模光纖進(jìn)行微納光纖的拉制,以提升模場與光柵的空間交疊區(qū)域,從而解決了成柵效率低下的問題。采用數(shù)值模擬方法獲得了微納光纖光柵Fabry-Perot干涉儀的光譜特性,對光纖幾何尺寸、光柵反射率等參數(shù)對其透射光譜的影響機(jī)理進(jìn)行了分析。通過研究該器件對溫度和折射率的響應(yīng)特性發(fā)現(xiàn),基模和高階模干涉峰對折射率和溫度的靈敏度不同,基于這一特性可以有效去除溫度的交叉敏感性問題。利用微納光纖光柵Fabry-Perot干涉儀進(jìn)行超聲探測是實(shí)現(xiàn)光聲成像的基礎(chǔ),我們對這種超聲傳感器的響應(yīng)機(jī)理和增敏方法進(jìn)行了深入研究。首先,理論分析了這種超聲傳感器的響應(yīng)機(jī)理,揭示了倏逝場對于這種聲傳感器靈敏度所起的關(guān)鍵性作用。實(shí)驗(yàn)上采用直徑為5.2μm的聲傳感器,實(shí)現(xiàn)了超聲靈敏度為1.845mV/kPa。在傳統(tǒng)單模光纖中采用相同方法制成的聲傳感器靈敏度僅為0.184mV/kPa,這說明微納光纖的倏逝場作用使靈敏度提升了10倍。進(jìn)一步研究了這種聲傳感器的輸出電壓功率譜和頻率響應(yīng)譜,測量了超聲檢測的方向依賴性。提出增強(qiáng)超聲靈敏度的兩個(gè)方法:一是通過增加光纖光柵的反射率,從而提高干涉條紋銳度,另一種是通過減小微納光纖直徑從而增強(qiáng)倏逝場作用。微納光纖光柵Fabry-Perot干涉型聲傳感器的研究是實(shí)現(xiàn)生物醫(yī)學(xué)光聲成像的基礎(chǔ),我們對這種聲傳感器的響應(yīng)原理、提高靈敏度的方法以及傳感特性進(jìn)行了深入研究。首先,理論分析推導(dǎo)了這種聲傳感器的響應(yīng)機(jī)理,揭示了倏逝場對于這種聲傳感器靈敏度所起的關(guān)鍵性作用。找出了進(jìn)一步提高靈敏度性能的兩個(gè)因素:一種是通過增加光纖光柵的反射率從而提高干涉條紋斜率的方法,另一種是通過減少微納光纖直徑從而增加模式折射率變化的方法。其次,實(shí)現(xiàn)了采用這種聲傳感器測量聲壓的方法,直徑為5.2μm的聲傳感器的靈敏度為1.845mV/kPa。而同樣條件下,普通光纖制成的聲傳感器的靈敏度為0.184mV/kPa,其靈敏度比普通單模光纖的高出10倍。最后,進(jìn)一步研究了這種聲傳感器的輸出電壓功率譜和頻率響應(yīng)譜,驗(yàn)證了微納光纖光柵Fabry-Perot干涉型聲傳感器的檢測方向特性�；谝陨涎芯�,本文采用微納光纖光柵Fabry-Perot干涉型超聲傳感器,實(shí)現(xiàn)了高靈敏度、高空間分辨率的生物醫(yī)學(xué)光聲成像。我們分析了生物組織的基本特性,研究了光聲信號的產(chǎn)生條件。然后根據(jù)光聲信號的聲壓波動方程對光聲信號的機(jī)理進(jìn)行了闡述,同時(shí)給出了采用的圖像重建方法及其數(shù)學(xué)推導(dǎo)過程。對成年人體的頭發(fā)進(jìn)行了光聲成像實(shí)驗(yàn),采用所研制的超聲傳感器,對由激光誘導(dǎo)的超聲信號進(jìn)行掃描探測,并對測得的信號在掃描柱面上的空間分布重構(gòu)空間光學(xué)吸收的二維分布圖像,光聲成像的空間分辨率達(dá)到了95μm。最后研究了測量位置數(shù)對光聲成像質(zhì)量的影響,發(fā)現(xiàn)提高測量位置數(shù)目能夠提高重建圖像的質(zhì)量和空間分辨率,但是二者的關(guān)系并不是一個(gè)線性的關(guān)系。在實(shí)際研究中,需要綜合考慮成像質(zhì)量、空間分辨率、掃描速度等因素,提出優(yōu)化的測量方案。
[Abstract]:Biomedical engineering is an application of the principle and method of natural science and engineering technology, the research of various organisms especially the structure of the human body, and other life science. Biomedical imaging technology is one of the most important parts in the field of Biomedical Engineering, by using optical microscopy, magnetic resonance and other physical means, access to space optical human organization the absorption distribution function, useful information extraction of eyes can not get, provide an important basis for early diagnosis of the disease, is of great significance to human health. Among them, photoacoustic imaging method is based on the photoacoustic effect, a new imaging method in ultrasonic signal detection for physical means, it combines the high penetration characteristics of high contrast the advantages of optical imaging and ultrasound imaging, becoming a hot research topic in the field of biomedical engineering. How to achieve high accuracy, High contrast, high spatial resolution photoacoustic imaging method has become the common goal of researchers in this field. Ultrasonic signal detection is key technology of photoacoustic imaging technology in the traditional piezoelectric sensor for ultrasonic signal detection, the sensitivity is relatively low, the response bandwidth, is not conducive to the realization of high performance imaging. In comparison, the detection sensitivity of ultrasonic sensor is high, and the characteristics of anti electromagnetic interference. In order to achieve high sensitivity photoacoustic imaging method with high contrast and high spatial resolution, we propose the use of micro nano optical fiber grating Fabry-Perot interferometer for ultrasound detection. Compared with the traditional ultrasonic sensor, this device is in the production of fiber diameter of only a few microns on, with higher spatial resolution and better image contrast characteristics. At the same time, with the strong transient micro nano optical fiber evanescent field And the high reflectivity of fiber grating writing technology, the response sensitivity of the ultrasonic signal is significantly improved. The main contents of this paper include: micro nano fiber grating Fabry-Perot interferometer is the physical basis of photoacoustic imaging, firstly the preparation process of the system, spectral properties and sensing properties were studied. The device is used 193nm excimer laser in micro nano optical fiber grating in writing and made two. Using multimode fiber draw micro fiber, overlapping regions to enhance the mode field and grating space, so as to solve the problem of low efficiency into grid. Numerical simulation method is used to obtain the spectral characteristics of micro nano fiber grating Fabry-Perot interferometer. The mechanism of fiber geometry, grating reflectivity parameters influence on the transmission spectra is analyzed. Through the research of the device in response to the temperature and refractive index. Now, the fundamental mode and higher-order mode interference peaks of refractive index and temperature sensitivity, cross sensitivity and it can be effectively removed based on temperature. Using micro nano fiber grating Fabry-Perot interferometer for ultrasound detection is based on photoacoustic imaging, we on the response mechanism of ultrasonic sensor and sensitization method the in-depth study. Firstly, the theoretical analysis of the response mechanism of the ultrasonic sensor, reveals the key role for the evanescent field sensitivity of the acoustic sensor. The experiment using acoustic sensor with diameter of 5.2 m, the sensitivity of ultrasonic acoustic sensor sensitivity 1.845mV/kPa. using the same method in the traditional single-mode fiber made the only 0.184mV/kPa, indicating that the micro nano optical fiber evanescent field sensitivity up to 10 times. Further study of the output voltage power spectrum of the acoustic sensor And the frequency response spectrum, ultrasonic detection direction measurement dependent. Two methods are proposed to enhance the sensitivity of ultrasound: one is by increasing the reflectivity of fiber grating, thereby improving the fringe sharpness, the other is by reducing the diameter of micro nano fiber enhanced evanescent field. Research on micro nano fiber grating interferometric acoustic Fabry-Perot the sensor is based on biomedical photoacoustic imaging principle, our response to the acoustic sensor and method of improving the sensitivity and sensing characteristics were studied. Firstly, the theoretical analysis of the response mechanism of the acoustic sensor, reveals the key role of evanescent field for the sensitivity of the acoustic sensor. Find out two factors to further improve the sensitivity of performance: one is the method of interference fringes by slope increasing reflectivity of fiber grating to improve, the other is through Reducing microfiber diameter increasing method the refractive index change. Secondly, the method of using the measurement of the pressure sensor, a diameter of 5.2 m acoustic sensor sensitivity is 1.845mV/kPa. and under the same conditions, the acoustic sensor sensitivity to 0.184mV/kPa ordinary optical fiber, its sensitivity is 10 times than the ordinary single-mode fiber. Finally, further research on the acoustic sensor output voltage power spectrum and frequency response spectrum, and validate the directional characteristics of micro nano fiber grating Fabry-Perot interferometric acoustic sensor. Based on the above research, this paper adopts the micro nano fiber grating Fabry-Perot interferometric ultrasonic sensor, to achieve high sensitivity, biomedical photoacoustic imaging with high spatial resolution. We analyzed the basic characteristics of biological tissues, on the condition of producing the photoacoustic signal. Then based on photoacoustic signal pressure The mechanism of wave equation on photoacoustic signal are described, and gives the image reconstruction methods and mathematical derivation. The adult body hair of photoacoustic imaging experiment, ultrasonic sensor was developed by the ultrasonic signal by laser induced by scanning probe, and the distribution of two-dimensional image signal measured in the spatial distribution of cylindrical scanning reconstruction of space optical absorption, spatial resolution photoacoustic imaging at 95 M. was also studied to measure the position of the number of photoacoustic imaging quality, improve the measuring position number can be found to improve the quality and spatial resolution of the reconstructed image, but the relationship between the two and the relationship is not a a linear. In the actual research, need to consider the imaging quality, spatial resolution, scanning speed and other factors, the measurement scheme optimization.

【學(xué)位授予單位】：暨南大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2014
【分類號】：R318;TH744.3

【參考文獻(xiàn)】

相關(guān)期刊論文 前1條

1 徐曉輝;李暉;;基于長焦區(qū)聚焦換能器的掃描光聲乳腺成像技術(shù)[J];物理學(xué)報(bào);2008年07期

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本文編號：1685306