本文選題：衍射層析成像 + 雷達成像��； 參考：《太原理工大學》2017年碩士論文

【摘要】：基于傅里葉的衍射投影定理的衍射層析成像系統(tǒng)在成像與目標識別方面具有突出的優(yōu)勢,因此被廣泛的應用于各種不同領域,尤其是醫(yī)學檢測,因其無創(chuàng)傷性,高精度的優(yōu)點,被人視為是能夠替代傳統(tǒng)的計算機斷層掃描(Computed Tomography,CT)的一個新技術,是國內(nèi)外研究熱點。與傳統(tǒng)雷達成像相比,衍射層析成像是一種重建目標函數(shù)的新技術。成像依照重建后所攜帶的目標信息可分為兩類:一類是獲取目標的大小、位置、形狀以及內(nèi)部結構等信息的成像可被稱為幾何成像或視覺成像;另一類旨在反映目標的物理或電學性質(zhì)變化,如折射率、介電常數(shù)、磁導率等信息,這類成像可被稱為物理成像。傳統(tǒng)雷達成像通常是對目標進行視覺成像,而基于衍射層析成像的雷達則是關注于目標電特性的變化�，F(xiàn)今已被成熟運用的物理成像的工業(yè)成品有計算機斷層掃描,因當時計算機技術的不足,成像算法都是以物理光學近似為前提將問題簡單化,因此,信號源只能采用X高頻射線等高頻信號,對人體輻射性強,無法適用于常規(guī)檢測。當目標尺寸與電磁波波長為同一量級時,此時衍射現(xiàn)象明顯,電磁波傳播路徑不能簡單的看作直線傳播,因此傅里葉衍射投影定理被提出,該定理以波動方程為基礎,通過計算包含衍射信息的散射場還原目標函數(shù),本質(zhì)上屬于逆散射問題。本文利用惠更斯原理,引入了原生源和次生源概念,通過公式推導,研究了源和場的關系,以及在射線理論或弱散射的條件下,場和源能互相線性表示。接著本文推導衍射層析成像原理的基本公式,討論了限制成像質(zhì)量的理論因素和實際因素。論文的主要工作即創(chuàng)新點如下述兩點所示。(1)分析了限制成像的因素,首次提出了雙聚焦成像系統(tǒng),同時采用視覺成像和物理成像的雙聚焦模式,達到高質(zhì)量的目標重建。視覺成像彌補了投影模式下衍射層析成像頻譜域的缺陷,還原目標輪廓信息,結合衍射層析成像提供的目標電特性變化,重建完備的目標圖像。論文通過理論分析與數(shù)據(jù)仿真,驗證該雙聚焦成像系統(tǒng)的可行性。(2)建立了基于雙聚焦的三維成像系統(tǒng),給出了完整的系統(tǒng)模型,論文通過仿真建模,分析了成像質(zhì)量與旋轉(zhuǎn)角度的關系。驗證了三維成像系統(tǒng)的可行性。本文提出了雙聚焦成像及三維成像系統(tǒng),論文對系統(tǒng)的成像性能進行了初步的探索,通過仿真對理論進行驗證。該研究對衍射層析成像的應用有重要意義和潛在價值。
[Abstract]:The diffraction tomography system based on Fourier diffraction projection theorem has outstanding advantages in imaging and target recognition, so it has been widely used in various fields, especially in medical detection, because of its advantages of non-traumatic and high accuracy. It is regarded as a new technology which can replace the traditional computed tomography (CTT), and it is a research hotspot at home and abroad. Compared with traditional radar imaging, diffraction tomography is a new technique to reconstruct objective function. Imaging can be divided into two categories according to the target information carried after reconstruction: one is the imaging of the size, position, shape and internal structure of the target, which can be called geometric imaging or visual imaging; The other is to reflect the changes of physical or electrical properties of the target, such as refractive index, permittivity, permeability and so on. This kind of imaging can be called physical imaging. Traditional radar imaging is usually used to visualize the target, while the radar based on diffraction tomography focuses on the change of the target's electrical characteristics. The industrial products of physical imaging that have been used now are computer tomography. Because of the insufficiency of computer technology at that time, imaging algorithms simplify the problem on the premise of physical and optical approximation. The signal source can only use X-ray and other high-frequency signals, which can not be used for routine detection because of its strong radiance to human body. When the size of the target is the same as the wavelength of the electromagnetic wave, the diffraction phenomenon is obvious, and the propagation path of the electromagnetic wave can not be simply regarded as the straight line propagation. Therefore, the Fourier diffraction projection theorem is proposed, which is based on the wave equation. By calculating the objective function of scattering field which contains diffraction information, it is essentially an inverse scattering problem. In this paper, the concepts of primary and secondary source are introduced by using Huygens principle. The relationship between source and field is studied by formula derivation, and the field and source energy are expressed linearly under the condition of ray theory or weak scattering. Then the basic formula of diffraction tomography principle is deduced, and the theoretical and practical factors that limit the imaging quality are discussed. The main work of this paper is innovation as shown in the following two points. (1) the factors limiting imaging are analyzed and a double focus imaging system is proposed for the first time. The dual focusing mode of visual imaging and physical imaging is used to achieve high quality target reconstruction. Visual imaging makes up for the defects in the spectral domain of diffraction tomography in projection mode, and restores the contour information of the target, and reconstructs the complete target image by combining the changes of the electrical characteristics of the target provided by the diffraction tomography. Through theoretical analysis and data simulation, the feasibility of the double focus imaging system is verified. (2) the 3D imaging system based on double focus is established, and the complete system model is given. The relationship between imaging quality and rotation angle is analyzed. The feasibility of 3D imaging system is verified. In this paper, double focus imaging and three dimensional imaging system are proposed. The imaging performance of the system is preliminarily explored, and the theory is verified by simulation. This study is of great significance and potential value for the application of diffraction tomography.
【學位授予單位】：太原理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TP391.41

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