A 94 GHz Passive Millimeter Wave Imaging System For Public Security

Millimeter waves are electromagnetic waves,whose frequencies are in the range of 30~300GHz,that is,the wavelength of 1~10 mm which is between the microwave and infrared light wave.So in addition to their characteristics common with microwaves a nd infrared waves,they also have many unique features.Compared with the microwave,in the case of the same antenna diameter,it is found that the millimeter waves have the advantages of narrow beam width,good directivity,excellent anti-jamming,high resolution and good penetrating property into the plasma.Comparing with infrared wave,millimeter waves have better penetration and strong diffraction performance and the attenuation degree of millimeter waves,in the atmospheric window by with the gas,smoke,fog and other material attenuation effect,is very small.So in severe weather conditions or military applications such as heavy smoke situation,the millimeter wave imaging technology is more advantageous than traditional photoelectric imaging technology.It has 24-hour uninterrupted mode of operation,and high resolution to be effectively identified the surrounding environment within the various target.Therefore,passive millimeter wave imaging technology is practically valuable in remote sensing,blind drop,navigation,security and other fields.Based on the millimeter wave theory,this paper develops a set of passive millimeter wave imaging system for the detection of prohibited items in the human body.The main contents of this paper are as follows:This paper briefly introduces the current situation of passive millimeter wave security system at ho me and abroad,and mainly discusses questions of passive millimeter wave imaging technology and concepts and methods of related radiation measurement.This paper summaries the current situation and future prospects of this field,at the same time,goes a deeper discussion about the nature of the related work,composition and core technology.Secondly,based on the theory of two-dimensional single-beam conical mechanical helical scanning and combining with passive millimeter wave imaging technology,we develop a set of passive millimeter wave imaging system.From the theoretical point of view to system performance,working principle and composition form,making the appropriate analysis and judgment,and we successfully operate the theoretical test on the 3 mm band detection imaging.Then,based on the data acquisition theory,we realize visual programming and the radiometer output signal acquisition and processing functions through the Lab VIEW platform.We conduct a comprehensive test on system performance to complete restoration function in the form of millimeter wave image in the target scene,at the same time,we give a comprehensive evaluation for system performance to provide a theoretical standard for good application in public safety testing of system.Finally,we go a further discussion about the super resolution processing method of the continuous multi-frame image according to the characteristics of the prospective passive millimeter wave imaging system.We use the POCS algorithm to improve the spatial resolution of low resolution(LR)images,and enhance the visual effect of the whole image.This is a good foundation for applying the POCS algorithm to the prospective passive millimeter wave imaging system to get a further improvement on the spatial resolution of the system.