TERAHERTZ WAVE REFLECTION IMAGING SYSTEM BASED ON BACKWARD WAVE OSC ILLATOR AND ITS APPL ICATION

Transcription

1 J. Infrared M illim. W aves Vol. 29, No. 1 February, 2010 : (2010) ,,, (, ) :..,. 0. 7THz,.,,. : ; ; ; : O439 : A TERAHERTZ WAVE REFLECTION IMAGING SYSTEM BASED ON BACKWARD WAVE OSC ILLATOR AND ITS APPL ICATION GE Xin2Hao, LV Mo, ZHONG Hua, ZHANG Cun2L in (Beijing Key Laboratory for Terahertz Spectroscopy and Imaging, Key Laboratory of Terahertz Op toelectronics, M inistry of Education, Department of Physics, Cap ital Normal University, Beijing , China) Abstract: A terahertz ( THz) wave reflection imaging system based on backward wave oscillator (BWO) was p resented. It is a new app roach to non2destructive testing. The intensity information of the terahertz wave after being reflected from the samp le surface or substrate was collected by a pyroelectric detector, and then imaged by computer. A number of samp les which had potential imaging app lications were tested by using 0. 7 THz radiation, including coins, badges, a model air2 p lane and some industrial samp les that contained p re2built defects. The experimental results reveal that THz radiation is highly transparent to many industrial materials, especially the m icrowave2absorbing material which is widely used in aero and space technologies. Key words: nondestructive testing; terahertz imaging; backward2wave oscillator(bwo) ; reflection imaging ( THz, 1THz = Hz) THz.,, [ 1 ],. (, BWO, Backward W ave O scillator),, 0. 1THz [ 1 ].,. (BWO ),,,..,, [ 2 ]. : , : Rece ived da te: , rev ised da te: : 973 (2007CB310408) ; ( ) : (19832),,,,, E2mail: loringe@126. com.

2 16 29 [ 3 ],,., [ 4] BWO.,,,,.,.,., GHz, [ 5], :,,.,,.,.,, :,,,, ;,,.,,,,.,., 1 BWO Fig. 1 Schematic layout of the reflective BWO THz imaging setup, [ 1 ].,,,. 2 BWO [ 6 ] 1, GHz, 0. 2mW. [ 7 ] ( Pyroelectric Detector)., 700GHz., 10Hz,, 20cm 30cm.,.,,,.,. 2, ( a) ( b) ( c), (d).,,., TDS,., 10cm 10cm, 1mm, 30m in. [ 8 ],.,., 700GHz.

3 1 : mm, 700GHz 0. 19mm., [ 9 ], [ 10 ]. [ 4 ],, 4. 3mm , 6mm, 0. 5mm, 1mm,, 1mm.,. 3 ( a), ( b), 140mm 85mm , 5, 6.,, ; ( 5) ( 4 ),.,.,,. 7,., 7 ( a) 12 ( b),.,.

4 29,,, m,,.,. 9, 9 ( b),,..,, ,.,.,,.,.,.,,,,. 4 (BWO ),, ( Pyroelectric Detector), 1 mm..,,,,,. (973 ) (No. 2007CB310408) ( 31 )

5 1 : X , 12 (1) : [ 2 ] Starck J, Cand s E J, Donoho D L. The curvelet transform for image denoiseing[ J ]. IEEE Transactions on Im age Pro2 cessing, 11 (6), 2002: [ 3 ] Pennec E L, Mallat S. Sparse Geometric image rep resenta2 tion with bandelets[ J ]. IEEE Transactions on Im age Pro2 cessing, 2005, 14 (4) : [ 4 ]Do M N, Vetterli M. The contourlet transform: an efficient directional multiresolution image rep resentation [ J ]. IEEE Transactions Im age on Processing, 2005, 14 ( 2 ) : [ 5 ]LU W en, GAO Xin2Bo, ZENG Kai, et al. Image quality e2 valuation metrics based on HWD [ J ]. J. Infrared M illim. W aves(,,,. HWD. ), 2009, 28 (1) : [ 6 ] ZHANG L in, FAN Zhi2Jun, WANG Sheng2Q ian, et al. Multiwavelet adap tive denoising method based on genetic al2 gorithm [ J ]. J. Infrared M illim. W aves (,,,.. ), 2009, 28 (1) : [ 7 ]AN Zhi2Yong, CU I J iang2tao, ZENG Zhi2Yong, et al. Im2 age retrieval based on radon and wavelet transform [ J ]. J. Infrared M illim. W aves (,,,. Radon. ), 2008, 27 (2) : [ 8 ]Cunha A L, Zhou J, Do M N. The nonsubsamp led contour2 let transform: theory, design, and app lications[ J ]. IEEE Transactions on Im age P rocessing, 2006, 15 ( 10 ) : [ 9 ]Laine A, Fan J, Yang W. W avelets for contrast enhance2 ment of digital mammography [ J ]. IEEE Engineering in M edicine and B iology, 1995, 14 (5) : [ 10 ] Bovis K, Singh S. Enhancement technique evaluation u2 sing quantitative measures on digital mammogram s [ C ]. The 5 th International Workshop on D igital M ammography, Toronto, Canada, 2000: [ 11 ] Suckling J, Parker J, Dance D, et al. The mammographic images analysis society digital mammogram database [ C ]. Exerp ta Medica, International Congress Series, 1069: ( 18 ) (No. 2006CB302901) (No ) ;.,. REFERENCES [ 1 ] Zhang Cunlin, Zhang Yan, Zhao Guozhong, et al. Tera2 hertz Sensing and Im aging [M ]. Beijing: National defense industry p ress(,,,.. : ), [ 2 ] Hess L, Cheville R. Nondestructive evaluation of ceram ic bearings using THz impulse ranging, Conference on Lasers and Electro2Op tics (CLEO) [ C ], 1, 729, [ 3 ]W iltse J. H istory of m illimeter and subm illimeter waves, IEEE Trans. M icrowave Theory Tech[ C ]. MTT232: , [ 4 ] Adrian Dobroiu, Masatsugu Yamashita, Yuichi N Ohshi2 ma, et al. Terahertz imaging system based on a backward2 wave oscillator[ J ]. A pplied O ptics, 2004, 43 ( 30) : [ 5 ]ChangM, Chou P, Lee H. Tomographic m icrowave imaging for nondestructive evaluation and object recognition of civil structures and materials [ C ]. Conference Record of The Twenty2N inth A silomar Conference on Signals, System s and Computers. 1996, 2: [ 6 ] Sasaki A, Nagatsuma T. Reflection2type CW 2m illimeter2 wave imaging with a high2sensitivity waveguide2mounted e2 lectro2op tic sensor[ J ]. Jpn. J. A ppl. Phys., 2002, 41: 83. [ 7 ]Lash A, Yundev D. Subm illimeter imaging with a pyroelec2 tric TV camera [ J ]. International Journal of Infrared and M illim eterw aves, 1984, 5: 489. [ 8 ]Lgffler T, Kress M, Thom son M, et al. Comparative per2 formance of terahertz em itters in amp lifier2laser2based sys2 tem s[ J ]. Sem icond. Sci. Technol., 2005, 20: S134. [ 9 ]M ei Z, Dou W. Performances of hyperbolical and spherical lens imaging system s at m illimeter wavelengths [ J ]. J. of E lectrom agn. W aves and A ppl., 2002, 16: [ 10 ]W ang S, Zhang X. Terahertz tomographic imaging with a Fresnel lens[ J ]. O pt. Photon. N ew s, 2002, 13: 59.