Near-field Millimeter Wave Imaging Calibration Method

In the system of passive millimeter wave imaging, the mechanism is the use ofelectromagnetic energy radiated by the target scene itself,the process by thereceiving terminal receives and further processed. The imaging system because ofits advantages, can be widely used with the actual situation of airport security,environmental testing, and so on. However, due to its low millimeter wave energyradiated from the target scene, in the process of propagation of electromagneticwave, because of the diffraction limited and uneven antenna beam.This causes thereceiver receives the image resolution is generally low, and we need to correct thisimaging system, which can be used to get a clearer picture.The main contents of thispaper is based on a focal plane of the linear array scanning system of passivemillimeter wave imaging systems theory, based on the following main contents tointroduce this system in the near-field imaging calibration method:Passive millimeter wave imaging system compared to infrared imaging, X-rayimaging,has many advantages.For example, although it also belongs to the infraredradiation, but due to different wavelengths of energy has led to their enormousdifference.Various types of material, the emission rate in the millimeter wave band,with a difference greater than infrared. In this article, summed up the advantages ofpassive millimeter wave imaging systems and conventional imaging methods.According to the millimeter-wave imaging process, we take the initiativeimaging system, semi-active and passive imaging system imaging systems docomparison. By study difference, and acceptance of different social structuresbetween research systems, and ultimately come to draw passive imaging systems aresummarized in the practical application of superiority.Combined with the basicprinciples of millimeter wave imaging, to take the focal plane imaging line scanimaging methods.This imaging method at compared to the other imaging methodshave advantages, also because of diffraction limited, uneven antenna beam causes itto produce spatial variation of the imaging process.Then we need an effectivecalibration method for passive imaging system calibration. Article, a mathematicalmodel of the spatial variation of the imaging process,used to influence the types ofspatially variable factors on the expression generated imaging during Imagingprocess.Based on the above mathematical model of the imaging process, in passivemillimeter wave imaging system, I will introduce of two near-field imagingcalibration methods, namely the calibration and external calibration,which is thecore of this thesis.Where the school is the use of a linear relationship between theinput criteria temperature and output voltage.By the two-point method in the system 70radiometer arrays is calibrated.Eventually in the input array radiometer sametemperature conditions, it is possible to output the same voltage.Using the externalcalibration standards for the point spread function of the image is estimated.Here Iuse wiener filtering algorithm, the image formed by further calibration,whichEffectively improve the passive millimeter wave imaging resolution of the image.In summary, the study of passive millimeter wave imaging system calibrationof the near-field image, which can effectively enhance the spatial resolution of theimage, while passive millimeter wave imaging system designed for high qualitywith a wide range of practical applications, it has very important significance.