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Terahertz Displacement and Thickness Sensor with Micrometer Resolution and Centimeter Dynamic Range

Authors
  • Han, Dae-Hyun
  • Kang, Lae-Hyong1
  • 1 Department of Mechatronics Engineering, Department of Flexible and Printable Electronics, and LANL-JBNU Engineering Institute-Korea, Jeonbuk National University, 567 Baekje-daero, Duckjin-gu, Jeonju-si, Jeonbuk 54896, Korea
Type
Published Article
Journal
Sensors
Publisher
MDPI AG
Publication Date
Nov 29, 2019
Volume
19
Issue
23
Identifiers
DOI: 10.3390/s19235249
PMID: 31795307
PMCID: PMC6928778
Source
PubMed Central
Keywords
License
Green

Abstract

Measuring distance and thickness simultaneously is important in biological, medical, electronic, and various industries. Herein, we propose a method for simultaneously measuring the displacement and thickness of transparent materials using a pulsed terahertz wave. For this technique, a beam splitter was used to design the optical path such that the terahertz wave would incident the specimen vertically to achieve centimeter measurement range and micrometer resolution. The measured terahertz waveform carries peak time information reflected from the upper and lower surfaces of the sample, and the thickness can be calculated using the time difference between the first and second reflected peaks. The displacement can also be calculated using peak time difference when the sample moves from the initial position to the changed position. For validation, an experimental test was performed using aluminum, acrylic, and glass plates. The results confirmed a measurement range of 1 cm with an error of less than 23 μm, and the thickness error was less than 8 μm.

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