本文關鍵詞：合成孔徑超聲成像信號相位畸變自適應校正技術研究　出處：《西南交通大學》2017年碩士論文　論文類型：學位論文

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

【摘要】：合成孔徑聚焦技術(SAFT)是超聲無損檢測研究學者們將合成孔徑雷達應用于超聲成像中的結果。超聲波優(yōu)點顯著,穿透力很強,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,因此受到青睞。但當超聲波在非均勻介質(zhì)中傳播時,各處速度產(chǎn)生的差異將引入波前誤差,材料內(nèi)部的精細結構顆粒會產(chǎn)生反射雜波,使得接收信號中攜帶噪聲,且傳播過程中會發(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。為解決相位畸變問題進而提高圖像分辨率,本文將研究超聲信號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,從中選擇采用合成聚焦方法。同時,利用波達方向窗函數(shù)消弱超聲波方向角對超聲信號的影響,從而達到優(yōu)化成像結果的目的。然后,詳細論述超聲合成聚焦信號中相位畸變的產(chǎn)生,分析其特性、建立數(shù)學模型并利用計算機模擬相位屏。常見的相位畸變校正方法是基于互相關系數(shù)的,根據(jù)傳統(tǒng)的鄰近互相關相位校正方法可衍生出自適應的互相關相位校正方法,本文研究一種利用解決優(yōu)化問題的函數(shù)argmax的改進的自適應互相關相位校正方法。最后,利用計算機仿真不同的缺陷點和醫(yī)學囊腫組織并加入相位屏,采用自適應及改進的自適應鄰近互相關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。對于單點和兩點仿真結果,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;對于多點仿真結果,改進的自適應校正圖像比自適應相位校正圖像比校正前的圖像峰值信噪比提高了 11.1%;對于囊腫組織仿真結果,相位校正后的圖像對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,由此證明自適應方法對于相位差校正的可行性和有效性。此外,利用Multi2000超聲實驗平臺采集實際數(shù)據(jù),獲得攜帶相位畸變的信號,同樣地,利用自適應及改進的自適應鄰近互相關相位畸變校正方法對原始數(shù)據(jù)進行處理,取得合成孔徑聚焦超聲圖像。對于單點和多點實驗數(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.

【學位授予單位】：西南交通大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TB559

【參考文獻】

相關期刊論文 前10條

1 李運才;王澤勇;;一種超聲合成孔徑成像優(yōu)化方法研究[J];信息技術;2016年02期

2 許澤帥;羊毅;蘭衛(wèi)華;董濤;劉玉;;基于H-V模型和Zernike法的激光大氣傳輸模擬[J];電光與控制;2014年07期

3 呂q，

本文編號：1380977