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Foreign Object Detection by Sub-Terahertz Quasi-Bessel Beam Imaging
Food Safety Research Group, Korea Food Research Institute, Backhyun 516, Sungnam, Gyeonggi-do 463-746, Korea
THz Photonics Creative Research Center, ETRI, Daejeon 305-700, Korea
* Author to whom correspondence should be addressed.
Received: 23 October 2012; in revised form: 4 December 2012 / Accepted: 11 December 2012 / Published: 20 December 2012
Abstract: Food quality monitoring, particularly foreign object detection, has recently become a critical issue for the food industry. In contrast to X-ray imaging, terahertz imaging can provide a safe and ionizing-radiation-free nondestructive inspection method for foreign object sensing. In this work, a quasi-Bessel beam (QBB) known to be nondiffracting was generated by a conical dielectric lens to detect foreign objects in food samples. Using numerical evaluation via the finite-difference time-domain (FDTD) method, the beam profiles of a QBB were evaluated and compared with the results obtained via analytical calculation and experimental characterization (knife edge method, point scanning method). The FDTD method enables a more precise estimation of the beam profile. Foreign objects in food samples, namely crickets, were then detected with the QBB, which had a deep focus and a high spatial resolution at 210 GHz. Transmitted images using a Gaussian beam obtained with a conventional lens were compared in the sub-terahertz frequency experimentally with those using a QBB generated using an axicon.
Keywords: terahertz imaging; sub-terahertz imaging; quasi-Bessel beam; axicon; foreign object detection; FDTD
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MDPI and ACS Style
Ok, G.; Choi, S.-W.; Park, K.H.; Chun, H.S. Foreign Object Detection by Sub-Terahertz Quasi-Bessel Beam Imaging. Sensors 2013, 13, 71-85.
Ok G, Choi S-W, Park KH, Chun HS. Foreign Object Detection by Sub-Terahertz Quasi-Bessel Beam Imaging. Sensors. 2013; 13(1):71-85.
Ok, Gyeongsik; Choi, Sung-Wook; Park, Kyung H.; Chun, Hyang S. 2013. "Foreign Object Detection by Sub-Terahertz Quasi-Bessel Beam Imaging." Sensors 13, no. 1: 71-85.