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[Editor's Pick] Current Optics and Photonics Vol. 6 no. 6 (2022 December)

사무국 hit 674 date 2022-12-26

Terahertz Nondestructive Time-of-flight Imaging with a Large Depth Range

Hwan Sik Kim1, Jangsun Kim2, and Yeong Hwan Ahn1*

 

Current Optics and Photonics  Vol. 6 No. 6 (2022 December) pp. 619-626
DOI: https://doi.org/10.3807/COPP.2022.6.6.619

 

 

Experimental setup: A schematic illustration of the THz- time of flight (TOF) imaging setup based on the asynchronous optical sampling (ASOPS) method.

  Fig. 1  Experimental setup: A schematic illustration of the THz- time of flight (TOF) imaging setup based on the asynchronous optical sampling (ASOPS) method.

 

Keywords: Terahertz spectroscopy and imaging, Three-dimensional imaging
OCIS codes: (110.6795) Terahertz imaging; (110.6880) Three-dimensional image acquisition; (300.6495) Spectroscopy, terahertz


Abstract
In this study, we develop a three-dimensional (3D) terahertz time-of-flight (THz-TOF) imaging technique with a large depth range, based on asynchronous optical sampling (ASOPS) methods. THz-TOF imaging with the ASOPS technique enables rapid scanning with a time-delay span of 10 ns. This means that a depth range of 1.5 m is possible in principle, whereas in practice it is limited by the focus depth determined by the optical geometry, such as the focal length of the scan lens. We characterize the spatial resolution of objects at different vertical positions with a focal length of 5 cm. The lateral resolution varies from 0.8–1.8 mm within the vertical range of 50 mm. We obtain THz-TOF images for samples with multiple reflection layers; the horizontal and vertical locations of the objects are successfully determined from the 2D cross-sectional images, or from reconstructed 3D images. For instance, we can identify metallic objects embedded in insulating enclosures having a vertical depth range greater than 30 mm. For feasible practical use, we employ the proposed technique to locate a metallic object within a thick chocolate bar, which is not accessible via conventional transmission geometry.

 

첨부파일
COPP vol 6. no. 6 (December issue) pp. 619-626.pdf