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Journal Article
Investigations on Practical Issues in Solid Immersion Lens Based Sub-Wavelength Terahertz Imaging Technique: System Stability Verification and Interference Pattern Removal
- Authors
- Da-Hye Choi, Jun-Hwan Shin, Il-Min Lee, Kyung Hyun Park
- Issue Date
- 2021-11
- Citation
- Sensors, v.21, no.21, pp.1-12
- ISSN
- 1424-8220
- Publisher
- MDPI
- Language
- English
- Type
- Journal Article
- Abstract
- Terahertz (THz) imaging techniques are attractive for a wide range of applications, such as non-destructive testing, biological sensing, and security imaging. We investigate practical issues in THz imaging systems based on a solid immersion lens (SIL). The system stability in terms of longitudinal misalignment of the SIL is experimentally verified by showing that the diffractionlimited sub-wavelength beam size (0.7 {\\lambda}) is maintained as long as the SIL is axially located within the depth-of-focus (~13 {\\lambda}) of the objective lens. The origin of the fringe patterns, which are undesirable but inevitable in THz imaging systems that use continuous waves, is analytically studied, and a method for minimizing the interference patterns is proposed. By combining two THz images obtained at different axial positions of the object and separated by {\\lambda}/4, the interference patterns are significantly reduced, and the information hidden under the interference patterns is unveiled. The broad applicability of the proposed method is demonstrated by imaging objects with different surface profiles. Our work proves that the resolution of conventional THz imaging systems can easily be enhanced by simply inserting a SIL in front of the object with high tolerance in the longitudinal misalignment and provides a method enabling THz imaging for objects with different surface profiles.
- KSP Keywords
- Beam size, Biological sensing, Depth of focus, High tolerance, Imaging techniques, Non-Destructive Testing(NDT), Objective lens, Practical issues, Security imaging, Surface profile, System stability
This work is distributed under the term of Creative Commons License (CCL)
(CC BY)
(CC BY)
