Research On Some Problems Of Terahertz Imaging Technology

Terahertz wave occupies the portion of the electromagnetic spectrum between infrared band and the electrical wave,which is high frequency, broadband,narrow antenna beam,penetrating and safe to the human body. Compared with the microwave imaging,it can be more easy to high resolution imaging.As to the infrared band and X-ray radio, the terahertz imaging would penetrate but non-destructive to the living body.Furthermore,it has quite good capacity to resist disturbance. So the terahertz imaging technology will be widely used in high resolution and micro target detection,which have a potential applied on military and civilian.Based on the varies of the terahertz sources,the recent terahertz imaging system can be divided into pulsed terahertz imaging system and continuous terahertz imaging system.The detecting signal of typical pulsed terahertz imaging system contains the amplitude and phase information,however, the terahertz wave, stimulated by Fs-laser, is broadband wave, which the bandwidth is around some THz.So it can not realize long distance transmission as the effected by the water vapor in the air.Moreover, the system is complex and high expensive. On the other side,continuous terahertz imaging system,using the single frequency THz source,works in the atmospheric window,which can transmit for a long distance.In order to detect the intensity of terahertz wave by directly using pyroelectric,Golay and photoconductive antennas(PDA),it only contains the amplitude without phase information.In this paper,we use the hybrid principle of the terahertz detection to image the object to overcome the weakness of the pulsed and continuous terahertz imaging system,which can transmit to long distance and extract the phase of object.This research consists of six parts as follows:1.Introduce the background,significance and status to the terahertz imaging technology.2.Introduce the basic principle of pulsed and continuous terahertz imaging technology.By the launch and detection mode of the puled and continuous terahertz imaging system, the designed of the hybrid terahertz imaging system is discussed.3.Deeply study the principle of the hybrid terahertz imaging system and calculate the modele parameters.Besides, simulate the imaging system by Matlab.4. Setup the optical instruments and design the acquisition module circuit of the hybrid terahertz imaging system. Measure the hybrid terahertz imaging system and analysis the experiment data.5.A continuous THz coherent imaging system is built, and the system is used to test the imaging results of the coins.6.Dry a conclusion and put forward the improvement scheme.