650 GHz imaging as alignment verification for millimeter wave corneal reflectometry

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Journal Title
Journal ISSN
Volume Title
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Date
2022-03-01
Major/Subject
Mcode
Degree programme
Language
en
Pages
Series
IEEE Transactions on Terahertz Science and Technology
Abstract
A system concept for online alignment verification of millimeter-wave, corneal reflectometry is presented. The system utilizes beam scanning to generate magnitude-only reflectivity maps of the cornea at 650 GHz and compares these images to a precomputed/measured template map to confirm/reject sufficient alignment. A system utilizing five off-axis parabolic mirrors, a thin film beam splitter, and two-axis galvanometric mirror was designed, simulated, and evaluated with geometric and physical optics. Simulation results informed the construction of a demonstrator system which was tested with a reference reflector. Similarity metrics computed with the aligned template and 26 misaligned positions, distributed on a 0.5 mm x 0.5 mm x 0.5 mm mesh, demonstrated sufficient misalignment detection sensitivity in 23 out of 26 positions. The results show that positional accuracy on the order of 0.5 mm is possible using 0.462 mm wavelength radiation due to the perturbation of coupling efficiency via beam distortion and beamwalk-off.
Description
Publisher Copyright: IEEE
Keywords
Biological and medical imaging, clinical instruments, Cornea, Couplings, Imaging, medical diagnostics, Optical imaging, Optical polarization, Optical sensors, Physical optics, THz imaging of cornea
Other note
Citation
Hu , Y , Baggio , M , Dabironezare , S , Tamminen , A , Toy , B , Ala-Laurinaho , J , Brown , E , Llombart , N , Deng , S , Wallace , V & Taylor , Z 2022 , ' 650 GHz imaging as alignment verification for millimeter wave corneal reflectometry ' , IEEE Transactions on Terahertz Science and Technology , vol. 12 , no. 2 , pp. 151-164 . https://doi.org/10.1109/TTHZ.2021.3140199