Design And Research Of Transmission System For QCL THZ Holographic Imager

This thesis presents the part the author takes upon in the project "Mobile QCL-THz Holographic Imager".Terahertz wave is the band between microwave and infrared ray. Thanks to the unique advantage, it has become a research focus in recent years, and it has also made significant progress in the imaging field. Many scholars at home and abroad have done a lot of research about terahertz imaging and they made great achievements. However, it is not easy to achieve high spatial resolution in terahertz under the premise of meeting the coherence length limited circumstances, because it will not only increase the difficulty of processing, but also increase the cost of the processing significantly.How to improve the spatial resolution of the entire transmission system on the condition that the coherence length is satisfied is the most important and difficult part in the project. In order to solve these problems, the author adopted the digital holographic technology, and introduced the principles and design methods of the digital holography seriously. After comparing different holographic imaging system, the author finally chose the pre-amplified coaxial digital holographic system which satisfies the system requirements well as the design.In order to verify whether the transmission system meets the requirements or not, the author calculate the position and the parameters of the mirror in the system under the principle that geometric optics and Gaussian beam propagation in space. After finishing the design of the object path and reference path based on the principle of holography, the author take out the simulation procedure with physical optics propagation method. After separate the incident wave of the system, the author gives out the distribution of the energy and the size of the spot in each mirror. As the shape of the output beam from the source is elliptical, in order to obtain a circular spot to improve the utilization of the beam, the author put forward a beam shaping system with the simulation results.