Study On Diffraction Tomography And Double Focusing And 3D Imaging System

The diffraction tomography system based on Fourier diffraction projection theorem has a prominent advantage in imaging and target recognition,and is widely used in various fields,especially medical detection,because of its noninvasive,high precision It is regarded as a new technology that can replace the traditional computer tomography(CT),which is a hot topic both at home and abroad.Compared with traditional radar imaging,diffraction tomography is a new technique to reconstruct the objective function.The imaging can be divided into two categories according to the target information carried after the reconstruction: one is the imaging of the information such as the size,location,shape,and internal structure of the target can be called geometric imaging or visual imaging;the other is to reflect the target Of the physical or electrical properties such as refractive index,dielectric constant,permeability and other information,such imaging can be called physical imaging.Conventional radar imaging is usually the visual imaging of the target,and based on the diffraction tomography of the radar is concerned about the target electrical characteristics of the changes.Nowadays,the industrial products with mature physical imaging have computer tomography.Because of the shortage of computer technology at that time,the imaging algorithm simplifies the problem of physical optical approximation.Therefore,the signal source can only use X high frequency ray High frequency signal,strong radiation on the human body,can not be applied to routine testing.When the target size 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 regarded as a straight line.Therefore,the Fourier diffraction projection theorem is proposed.Based on the wave equation,Diffraction information of the scattering field to restore the objective function,essentially belong to the inverse scattering problem.In this paper,we use the Huygens principle to introduce the concept of primitive source and dimension source.The relationship between source and field is deduced by formula,and the field and source energy are linearly expressed under the condition of ray theory or weak scattering.Then,the basic formula of the principle of diffraction tomography is deduced,and the theoretical and practical factors to limit the image quality are discussed.The main work of the paper innovation point as shown in the following two points.(1)The factors that limit the imaging are analyzed.The double focus imaging system is proposed for the first time,and the double focus mode of visual imaging and physical imaging is used to achieve high quality target reconstruction.The visual imaging compensates the defects of the diffractiontomography domain in the projection mode,restores the target contour information,and reconstructs the complete target image in combination with the change of the target electrical characteristic provided by the diffraction tomography.The feasibility of the dual focus imaging system is verified by theoretical analysis and data simulation.(2)A three-dimensional imaging system based on double focusing is established,and a complete system model is given.The relationship between image quality and rotation angle is analyzed by simulation modeling.The feasibility of the 3D imaging system is verified.In this paper,a dual focus imaging and a three-dimensional imaging system are proposed.The imaging performance of the system is explored,and the theory is verified by simulation.This study is of great importance and potential for the application of diffraction tomography.