275–305 GHz FM-CW Radar 3D Imaging for Walk-Through Security Body Scanner
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Published:2023-03-22
Issue:3
Volume:10
Page:343
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ISSN:2304-6732
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Container-title:Photonics
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language:en
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Short-container-title:Photonics
Author:
Ikari Tomofumi12, Sasaki Yoshiaki1, Otani Chiko13
Affiliation:
1. RIKEN Center for Advanced Photonics, RIKEN, Sendai 980-0845, Miyagi, Japan 2. Spectra Design Ltd., Otawara 324-0403, Tochigi, Japan 3. Department of Physics, Tohoku University, Sendai 980-8578, Miyagi, Japan
Abstract
Imaging using millimeter waves (MMW) and terahertz (THz) waves can help inspect hazardous materials hidden beneath clothing in a non-contact and non-invasive manner. A 3D terahertz imaging system for security gate applications in the 275–305 GHz range was developed and experimentally demonstrated to detect concealed objects carried by pedestrians. This system performs 3D measurements by combining depth detection using frequency-modulated continuous wave (FM-CW) radar, vertical scanning of the detection spot using a 1D high-speed mechanical beam scanner, and horizontal movement of the irradiated area and detection spot as the pedestrian walks. The high-speed beam scanner comprises an F-Theta telecentric lens and a polygon mirror. It has a vertical line scan rate of 142 lines/s and spatial resolution of ~10 mm, consistent with the design value, and a depth resolution of ~7 mm, which is 40% larger than the theoretical value estimated from the FM-CW radar principle. The depth-dependent lateral distortion in 3D images, known as telecentricity, measured using the body scanner imaging system, was also evaluated. Consequently, images with the same magnification were obtained at a range of more than 500 mm of focus depth. Finally, the detection of concealed objects carried by pedestrians was demonstrated, showing that the system can work for a pedestrian walking at speeds from 4 km/h to 7 km/h.
Funder
Terahertz optical science and technology in semiconductors
Subject
Radiology, Nuclear Medicine and imaging,Instrumentation,Atomic and Molecular Physics, and Optics
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