Quality Improvement and Noise Reduction of Terahertz Continuous Wave Imaging
SUN Jian-zhong1,2, ZHANG Le2*, GAO Fei1, LI Jiu-sheng1
1. College of Computer Science & Technology, Zhejiang University of Technology, Hangzhou 310014, China
2. Centre for THz Research, China Jiliang University, Hangzhou 310018, China
Abstract：Terahertz wave imaging has many advantages such as small ionizing radiation and high discrimination of organic matter, so it is very suitable for non-contact, non-destructive imaging detection. However, this imaging method is susceptible to unavoidableproblems such as disturbance of electromagnetic environment and fluctuation ofequipment power, which makes it difficult to obtain high resolution terahertzimages. In this paper, terahertz imaging is realized by using the terahertz continuous-wave source imaging system. The terahertz images of four samples of cards, leaves, coins and keys are denoised by ourimproved threshold gray-scale transformation algorithm. Then, the images are sharpened and enhanced by the Laplacian operator. The results are evaluated bymean square error and peak signal to noise ratio estimation. After the denoising, the estimated peak signal to noise ratio of some samples increased by 4～5 dB, so the image quality was improved obviously. This research proves that the built-up terahertz imaging system has a pomosing application prospect.
Key words：Terahertz; Image resolution; Imaging; Peak signal to noise ratio
[1] Jonathan O, Jerome M, Jeremy L. Optics Express, 2013, 21(4): 4817.
[2] Paul D, Alex V, James K. Applied Physics Letters, 2013, 103(18): 181112.
[3] Alvydas L, Maris B, Sebastian B. J. Infrared Millimeter and Terahertz Waves, 2014, 35(1): 63.
[4] GUO Lan-tao, MU Kai-jun, DENG Chao, et al(郭澜涛, 牧凯军, 邓 朝, 等). Infrared and Laser Engineering(红外与激光工程), 2013, 1: 51.
[5] CHEN Su-guo, HOU Lei, LOU Xiao, et al(陈素果, 侯 磊, 楼 骁, 等). Xi’an University of Technology(西安理工大学学报), 2013, 2: 127.
[6] Tan Z, Zhou T, Cao J. IEEE Photonics Technology Letters, 2013, 25(14): 1344.
[7] Zhao J, Chu W, Guo L. Scientific Reports, 2014, 4: 3880.
[8] LI Qi, XIA Zhi-wei, DING Sheng-hui, et al(李 琦, 夏志伟, 丁胜晖, 等). Industrial Control Computer(红外与激光工程), 2012, 41(2): 517.
[9] FANG Li, ZHANG Ping(方 莉, 张 萍). Journal of Chinese Computer Systems(工业控制计算机)，2010, 23(11).
[10] TAN Ru, LI Ting-ting, LI Wei-wei, et al(谭 茹, 李婷婷, 李伟伟, 等). Journal of Chinese Computer Systems(小型微型计算机系统)，2014, 35(1): 137.
