發(fā)布時(shí)間：2018-01-05 01:23

  本文關(guān)鍵詞：合成孔徑超聲成像信號(hào)相位畸變自適應(yīng)校正技術(shù)研究　出處：《西南交通大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 合成孔徑 波達(dá)方向窗函數(shù) 相位畸變 互相關(guān)系數(shù) 圖像處理

【摘要】：合成孔徑聚焦技術(shù)(SAFT)是超聲無(wú)損檢測(cè)研究學(xué)者們將合成孔徑雷達(dá)應(yīng)用于超聲成像中的結(jié)果。超聲波優(yōu)點(diǎn)顯著,穿透力很強(qiáng),傳播方向良好,不存在明確的衍射,且具有快速且高效的特點(diǎn),因此受到青睞。但當(dāng)超聲波在非均勻介質(zhì)中傳播時(shí),各處速度產(chǎn)生的差異將引入波前誤差,材料內(nèi)部的精細(xì)結(jié)構(gòu)顆粒會(huì)產(chǎn)生反射雜波,使得接收信號(hào)中攜帶噪聲,且傳播過(guò)程中會(huì)發(fā)生聲波衰減,材料表面起伏(即不平整)及衍射這一系列因素會(huì)造成超聲圖像攜帶相位畸變,因而圖像分辨率低。為解決相位畸變問(wèn)題進(jìn)而提高圖像分辨率,本文將研究超聲信號(hào)中的相位畸變并校正。首先,本文介紹了四種超聲合成聚焦成像方式及其各自優(yōu)缺點(diǎn),從中選擇采用合成聚焦方法。同時(shí),利用波達(dá)方向窗函數(shù)消弱超聲波方向角對(duì)超聲信號(hào)的影響,從而達(dá)到優(yōu)化成像結(jié)果的目的。然后,詳細(xì)論述超聲合成聚焦信號(hào)中相位畸變的產(chǎn)生,分析其特性、建立數(shù)學(xué)模型并利用計(jì)算機(jī)模擬相位屏。常見(jiàn)的相位畸變校正方法是基于互相關(guān)系數(shù)的,根據(jù)傳統(tǒng)的鄰近互相關(guān)相位校正方法可衍生出自適應(yīng)的互相關(guān)相位校正方法,本文研究一種利用解決優(yōu)化問(wèn)題的函數(shù)argmax的改進(jìn)的自適應(yīng)互相關(guān)相位校正方法。最后,利用計(jì)算機(jī)仿真不同的缺陷點(diǎn)和醫(yī)學(xué)囊腫組織并加入相位屏,采用自適應(yīng)及改進(jìn)的自適應(yīng)鄰近互相關(guān)相位畸變校正方法處理含有相位差的仿真數(shù)據(jù),利用合成孔徑超聲成像方式成像。對(duì)于單點(diǎn)和兩點(diǎn)仿真結(jié)果,相位校正后的圖像分辨率比校正前的有在2.5%～10.9%范圍內(nèi)不同程度提高;對(duì)于多點(diǎn)仿真結(jié)果,改進(jìn)的自適應(yīng)校正圖像比自適應(yīng)相位校正圖像比校正前的圖像峰值信噪比提高了 11.1%;對(duì)于囊腫組織仿真結(jié)果,相位校正后的圖像對(duì)比度噪聲比值比加相差的有在23.9%～52.7%范圍內(nèi)不同程度提高,由此證明自適應(yīng)方法對(duì)于相位差校正的可行性和有效性。此外,利用Multi2000超聲實(shí)驗(yàn)平臺(tái)采集實(shí)際數(shù)據(jù),獲得攜帶相位畸變的信號(hào),同樣地,利用自適應(yīng)及改進(jìn)的自適應(yīng)鄰近互相關(guān)相位畸變校正方法對(duì)原始數(shù)據(jù)進(jìn)行處理,取得合成孔徑聚焦超聲圖像。對(duì)于單點(diǎn)和多點(diǎn)實(shí)驗(yàn)數(shù)據(jù),相位校正后的圖像分辨率比校正前的有在9.1%～17.1%范圍內(nèi)不同程度提高,再次驗(yàn)證了相位校正算法處理相差的可行性和有效性。
[Abstract]:Synthetic aperture focusing technique (SAFT) is ultrasonic nondestructive testing research of scholars of synthetic aperture radar used in ultrasonic imaging results. Ultrasound has many significant advantages, strong penetrating power, the propagation direction is good, there is no clear diffraction, and has the characteristics of fast and efficient, because this is favored. But when the ultrasonic wave propagation in an in a homogeneous medium, the difference throughout the speed generated will introduce the wavefront error, the fine structure of particles inside the material will have a reflection of clutter, which carry noise in the received signal, and the occurrence of acoustic attenuation in the transmission process, the material surface (i.e. not flat) and a series of factors will cause the diffraction of ultrasound image carrying phase the distortion of image resolution is low. In order to solve the problem of phase distortion and improve the image resolution, this paper will study the phase distortion in ultrasonic signal and correction. Firstly, this paper introduces four kinds of ultrasound Synthetic focusing imaging methods and their respective advantages and disadvantages, the synthetic focusing method from it. At the same time, the influence of the direction of arrival angle of window function weaken the ultrasonic ultrasonic signal, so as to achieve the purpose of optimizing the imaging result. Then, discussed in detail the ultrasonic synthesis phase distortion of focal signal in production, analyzes its characteristics, mathematical model and Simulation of phase screen by computer. The phase distortion correction method is common cross correlation coefficient based, according to the traditional adjacent cross-correlation phase correction method can be derived according to the cross-correlation phase correction method, correction method in this paper using an improved argmax function to solve the optimization problem of the adaptive cross-correlation phase. At last by computer simulation, the defect of different medical and cyst tissue and join the phase screen, using adaptive and improved adaptive neighborhood correlation phase A distortion correction method with the simulation data of the phase difference, using synthetic aperture ultrasound imaging mode imaging. For single point and two simulation results, the image resolution is improved after phase correction in 2.5% ~ 10.9% range in different degrees than before correction; for the simulation results, the improved adaptive image correction than adaptive phase correction image than before correction image peak signal-to-noise ratio is increased by 11.1%; the cyst tissue simulation results, phase corrected image contrast noise ratio and phase difference increased from 23.9% to 52.7% in the range of different degrees, which proves that the adaptive method for phase difference correction is feasible and effective. In addition, the use of Multi2000 ultrasonic experimental platform the actual data collection, obtain the signal carrying phase distortion similarly, adjacent cross-correlation phase distortion correction based on adaptive and improved The method used for processing the raw data, to obtain synthetic aperture ultrasonic image. For the single point and multiple point experimental data, image resolution phase correction after the increase in the 9.1% to 17.1% range different than before correction, again to verify the feasibility and effectiveness of the algorithm is the correction phase.

【學(xué)位授予單位】：西南交通大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TB559

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本文編號(hào)：1380977