On Algorithms Of Active Millimeter-Wave Imaging For Safety Check

In recent years,the problem of safety check has drawn more and more attention.The conventional safety check techniques can no longer meet the demands of the modern safety check due to its low efficiency and other limitations.However,the millimeter-wave(MMW)imaging is a novel and efficient safety check technique,which is able to detect not only metal targets concealed by common clothing but also modern threats such as plastic handguns or ceramic knives,liquid explosives and other dangerous items.Additionally,the MMW imaging systems for safety check pose no ionizing radiation injury to the human body.Therefore,it has become one of the main safety check technologies that people choose at present.The paper mainly studies the MMW imaging algorithms for safety check.The main work and contributions of this paper are as follows:(1)Based on the 2-D Back Projection(BP)algorithm and 2-D MMW holographic imaging algorithm,the quality of 2-D MMW near-field imaging is analyzed.And the results of the analysis show that the quality of 2-D MMW near-field imaging depends on the model approximation,the imaging distance,the array spacing and other factors.Therefore,a novel 2-D MMW near-field imaging algorithm is proposed.Monte Carlo simulation results show that the novel algorithm can achieve better image quality than conventional algorithms.(2)The 2-D MMW near-field imaging method based on the multi-frequency space de-aliasing is studied.To solve the image blurring problem caused by spatial spectrum aliasing,the problem of target image reconstruction is described as a nonlinear optimization problem,and then the Least Square Method(LSM)is used to solve the problem.Finally,MATLAB simulation results verify that the novel 2-D MMW near-field imaging multi-frequency space de-aliasing algorithm can achieve better image quality.(3)The wide-band 3-D MMW imaging methods are studied,which mainly include:(1)3-D MMW imaging approximation method based on the 2-D BP algorithm;(2)the novel Inverse Distance Weighted(IDW)interpolation 3-D MMW holographic imaging algorithmis proposed.Finally,MATLAB simulation results show that the IDW interpolation algorithm can achieve better image quality than the sinc interpolation algorithm and the stolt interpolation algorithm.