Design Of Imaging Servo Scanning Mechanism And Research On Channel Equalization Algorithms For Passive Terahertz Imaging

Terahertz passive imaging is a passive detection method for security inspection.Terahertz has a better imaging spatial resolution than millimeter wave because of its shorter wavelength.At the same time,it does not emit electromagnetic wave,so it will not cause damage to human body.It has a good application prospect in the field of security inspection.The use of terahertz passive imaging technology for security inspection has become a new trend in the development of human security technology at China and abroad.Servo scanning structure is an important part of terahertz passive imaging system,which drives the antenna to move,and achieves scanning imaging of human body area.This thesis completes the design of servo scanning mechanism based on the performance requirements of the actual project.Due to the limitation of system manufacturing cost and process,there is a problem of inconsistent response between different channels in terahertz linear array scanning imaging system,which leads to band noise in imaging and makes it difficult to detect hidden targets.In this paper,two channel equalization methods are proposed for channel imbalance,which can reduce the adverse effects of channel imbalance.This thesis relies on the actual scientific research projects to carry out research.The main research contents include:(1)Based on the basic theory of terahertz passive imaging technology,the mathematical models of radiation characteristics and brightness temperature of objects in terahertz band are studied,and the technical advantages of terahertz passive imaging are analyzed.(2)According to the task goal of the project,the scheme analysis and comparison of the scanning servo mechanism are completed,and the mechanical structure,scanning mode and working flow of the system are determined.(3)The key parameters of the servo system and the relationship between the system interface are analyzed and demonstrated.The main components are selected,the scanning characteristic curve is studied,and the realization scheme of the servo mechanism is designed.(4)The channel equalization algorithm based on scenario assumption is studied.The traditional two-point calibration method is improved.The calibration source is changed from the external "hot and cold calibration source" to two regions in the image.The new method can reduce the hardware cost and the repeated debugging process in the system operation.(5)The channel equalization algorithm based on Kalman filter is studied.Aiming at the problem of time-consuming and memory-occupying of traditional Kalman filter algorithm,the frame-dividing algorithm of Kalman filter is improved,which reduces the space and time complexity and improves the real-time performance.