Millimeter Wave Radiation Imaging And Image Processing Techniques

Because of strong penetration, providing more specific information of objects and all-time, all-weather ability to work, passive millimeter-wave imaging has been widely applied in fields of remote sensing, military affairs, public security and environmental monitoring. Passive millimeter-wave imaging is to receive the radiation emitted by target and its background using millimeter-wave radiometer, and display the signal obtained with a pseudo-color image in proportion. Owing to the restrictions of antenna, equipment and environment, the resolution of images is low. To improve the resolution, two key-techniques are studied:synthetic aperture radiation imaging and image processing. The whole study mainly includes three parts:(1) Introduce the advantages of passive millimeter imaging technology, sketching the current research status of synthetic aperture radiometer at homeland and abroad. And the common theory and principles of passive millimeter wave imaging are introduced, which consist of the measuring principle of MMW radiometer, the relationship between antenna temperature and the radiometer power and the advantages and disadvantages of the full power radiometer and comparative radiometer. The millimeter wave radiation characteristic model of the relationship between the bright temperature and object’s thickness and complex permittivity is established, using coherent method.(2) Millimeter wave synthetic aperture radiation imaging is based on the Van Cittert-Zernike theorem, improving the resolution of millimeter wave radiometric image in the circuit. Several related technical problems like sparse array antenna, inversion methods, the spatial resolution and the image sensitivity are studied. Some results under certain simulation environments are presented.(3) Applying methods of image processing to millimeter wave radiometric image can improve the resolution. Some simulation results of noise reduction, image restoration, image reconstruction, and image segmentation are given, such as mathematical morphology in grayscale image processing, blind deconvolution image restoration algorithm, the Bicubic interpolation method and the watershed algorithm.In this thesis, the relationship between objects’millimeter wave radiometric image and its radiation characteristic and the methods of improving the resolution of millimeter wave radiometric image are both studied. It is believed that these results have important significations and practical values for this kind of engineering design and applications.