The Generation of Bessel Beam and Its Application in Millimeter Wave Imaging
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The Generation of Bessel Beam and Its Application in Millimeter Wave Imaging Hongfu Meng & Bo Xiang & Jinglei Zhang & Wenbin Dou & Yanzhong Yu
Received: 20 May 2013 / Accepted: 11 November 2013 / Published online: 26 November 2013 # Springer Science+Business Media New York 2013
Abstract In this paper, the zero-order Bessel beam at W band is generated by using a diagonal horn, a convex lens, and an axicon. The generated Bessel beam has a beam spot size of 5.5mm and can propagate with a distance longer than 100mm. Several imaging experiments with the generated zero-order Bessel beam are done. The results show that the millimeter wave imaging system with the generated Bessel beam can be used to detect object as small as 1mm. Keywords Axicon . Bessel Beams . Diagonal horn . Gaussian beam . Imaging . Millimeter wave
1 INTRODUCTION Under ideal conditions, the nondiffracting beams can propagate a long distance without suffering from diffraction. They have attracted many researchers’ interests in the past decades [1]. Their potential applications in wireless power transmission, optical interconnections, nondestructive testing (NDT), and imaging make them very popular.
H. Meng (*) : B. Xiang : J. Zhang : W. Dou : Y. Yu State Key Laboratory of Millimeter Waves, Southeast University, Nanjing 210096, People’s Republic of China e-mail: [email protected] B. Xiang e-mail: [email protected] J. Zhang e-mail: [email protected] W. Dou e-mail: [email protected] Y. Yu e-mail: [email protected] Y. Yu College of Physics & Information Engineering, Quanzhou Normal University, Quanzhou, Fujian 362000, People’s Republic of China
J Infrared Milli Terahz Waves (2014) 35:208–217
209
The first class of nondiffracting beams was introduced by Durnin in 1987 [2]. By solving the Helmholtz equation in the circular cylindrical coordinate system, the fields are described in terms of nonsingular Bessel functions as: E ðr; φ; zÞ ¼ E 0 J l ðk r rÞexpð− jk z zÞexpð−jlφÞ
ð1Þ
where Jl is the lth-order Bessel function, so they are named Bessel beams. The intensity distribution of the zero-order Bessel beam has a maximum in the central and all the higherorder Bessel beams have zero on axis surrounded by concentric rings. Since Durnin’s work on Bessel beams, many studies about the nondiffracting beams in optical domain have been done. Various approaches for the generation of the Bessel beams in the optical region are put forward, such as the axicon [3–6], the computer generated holograms (CGH) [7], and the diffractive phase elements [8]. The generations and applications of Bessel beams have also been widely investigated in many other fields, such as acoustics [9]. However, there are few studies on the Bessel beams in millimeter and sub-millimeter wavebands. The axicon and CGH have been used to generate Bessel beams at millimeter wave frequencies experimentally [10–12] and the simulation studies of the binary optical elements have also been proposed [13, 14]. The applications of the Bessel beam in THz imaging are investigated in [15, 16]
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