Research On Active And Passive Hybrid Millimeter Wave Imaging Target Recognition Method Based On Information Fusion

Terrorism and violent crimes occur frequently on a global scale,posing a huge threat to people's lives.In order to prevent such violent and terrorist incidents,it is particularly important to improve the security capability of public places.Millimeter wave imaging technology has strong penetrating ability for clothing,high imaging resolution,and more advantages in radiation safety protection,which is suitable for human security.In this paper,the concept of information fusion is introduced into the MMW active and passive imaging system.In this paper,active millimeter wave imaging algorithms,image preprocessing and data fusion methods are studied.The main research contents include the following three aspects:Firstly,two dimensional holographic algorithms based on spherical wave expansion and two dimensional exact holographic reconstruction based on angular spectrum theory are derived.The azimuth resolution is verified by simulation and the best sampling plane range is determined.Based on the prior beam and imaging distance,diffraction holograms and inversion reconstruction images of target line pairs with complex reflectance of 1 in extremely narrow beam,ordinary beam and ultra-wide beam are observed.The antenna beam in the holographic simulation was optimized,and the main lobe width was changed from 8.8° in the narrow beam to 57.0° in the wide beam,effectively improving the reconstructed image quality.In addition,MATLAB and FEKO software are used to establish PEC metal bar through joint simulation.In the single sending and receiving mode,the reconstruction effect of transmitting antenna with wide-beam half-wave oscillator is better than that of narrow-beam horn antenna,and the minimum relative error of reconstructed data is as low as 6%.Secondly,the image preprocessing methods,including filtering,image enhancement and edge detection,are discussed.Morphological filtering is applied to image processing,and some methods such as gray scale change and histogram correction are discussed.Image gradient,Prewitt operator and Canny operator are used to preprocess millimeter wave images.Prewitt operator can effectively identify key targets and detect whether people are carrying hidden objects,with a success rate of 75%.Thirdly,the concept of information fusion is introduced into millimeter-wave imaging system.As multi-source sensors,visible camera,millimeter-wave radiometer and millimeter-wave active radar are proposed.The hardware fusion block diagram of millimeter-wave active and passive composite imaging system and the software fusion block diagram based on decision-level fusion are proposed.Focus on pixel level fusion.The fusion images were quantitatively analyzed by subjective evaluation and objective indexes such as information entropy and definition.Wavelet transform simulation USES two registered multi-focus grayscale images for fusion,IHS transform simulation to achieve the high resolution of the color image synthesis.Information entropy and clarity are effectively improved,with the maximum improvement rate reaching 31.9%.The conclusion is that the fused image is superior to the source image.The pixel-level fusion of images in multi-source MMW imaging system lays a foundation.In summary,the research on active millimeter wave accurate holographic reconstruction algorithm,image preprocessing and data fusion in this paper provides basic theoretical support for the application of millimeter wave imaging system in human security.