CAO Bing-hua1，LI Su-zhen1*，CAI En-ze1，FAN Meng-bao2，GAN Fang-xin1
1. School of Information and Control Engineering, China University of Mining and Technology, Xuzhou 221116, China
2. School of Mechatronic Engineering, China University of Mining and Technology, Xuzhou 221116, China
Abstract：In recent years, with the rapid development of photonics technology and microelectronic technology, the application fields of terahertz imaging has become more and more extensive, and have achieved some nice achievements in the fields of medicine and food monitoring, biomedical imaging, non-contact and non-destructive testing of devices, as well as the research on relics and work of arts,etc. This paper summarizes the superior performance of terahertz waves in imaging compared to microwaves and x-rays. Then, from the perspective of the light source, the terahertz continuous wave imaging and the terahertz pulse wave imaging are compared, including the system principle, imaging characteristics and their advantages and disadvantages. For the development of THz imaging technology in the past 20 years, this paper is aimed to introduce the four imaging methods including THz-TDS, focal plane array detection, near-field and compressed sensing. Their basic principles and development trends are also included.Among them, the terahertz time-domain spectroscopy technology takes the classical reflective spectral imaging system as an example, focusing on the basic principles of spectral imaging, the development trend of the technology and its practical cases in the pharmaceutical field. Moreover, on this basis, the terahertz source and the corresponding detector are introduced. In the part of focal plane array detection imaging technology, it consists of three kinds of current mature array cameras, which include CCD type, Microbolometer type and CMOS type. Near-field imaging technology is divided into two major imaging types. One is aperture imaging, and another is tip-scattering. The former summarizes typical near-field aperture illumination modes and collection mode. The latter includeslaser terahertz emission microscope and scanning tunneling microscope. The content covers the basic principles of system, the progress of current research, and the problems that remain in the development of the technology.The last part introduces an imaging method called compressed sensing, which can reduce the sampling rate of the system. It compares with the raster scanning sampling method used in terahertz spectral imaging technology. Furthermore, sincethe optical modulator is the key component of subsampling, its improved optimization process is analyzed. Improved algorithmsare also included.
Key words：Terahertz wave；THz-TDS；Focal plane array detection；Near field imaging；Compressed sensing
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