The Research Of Lens Used In Terahertz Imaging System

Terahertz imaging technology has a wide application prospect in the security, medicaland other fields, which has become the current research hotspot. In this paper, the technologyof the integrated lens antenna, which is composed of on-chip antennas and a dielectric lenses,is mainly studied as the front-end of THz imaging system, making full use of the advantagesof monolithic integrated systems, such as low cost, small size, light weight, strongadaptability, and so on. The research thought is from a single-pixel lens antenna to the multi-pixel lens antenna array. The extended hemispherical lens and fly-eye microlens are twomajor solutions applied to a multi-pixel system. Several terahertz on-chip antennas arecompared with the combination of theory and electromagnetic simulations in340GHzfrequency point, and the log periodic antenna is select as the radiation unit. The principles ofthe extended hemispherical lens are analyzed, and the design rules of silicon, quartz andpolyester material lens are given. Combined with the log periodic antenna, the optimizedsimulation results of the single pixel lens antenna system are given, and the test of radiationpattern is also completed. The results of simulation and test are in good agreement. The2×2lens antenna array is designed respectively based on the extended hemispherical lens andthe fly-eye microlens. The simulation results show that the beam separation characteristicsand the gain are all good. For the extended hemispherical lens antenna array, if the Strehlratio is not less than0.63and the manufacturing technique has not changed, a silicon lenswith30mm diameter has the maximum capacity of2×2antenna array, and a quartz lens with30mm diameter has the maximum capacity of4×4antenna array. For the fly-eye microlensantenna array, the manufacturing technique is the major difficulty. The crystal materials aredifficulty to machine with high cost, and the non-crystal materials, such as polyester, can bemachined by3D printing technology. Therefore, the fly-eye microlens scheme with non-crystal materials is a more reasonable choice. In summary, the antenna array based on theextended hemispherical lens is relatively easy to machine and has a better directivity, whilethe machine of the microlens is relatively difficult and has a better beam separation andexpansion.