650 GHz Imaging as Alignment Verification for Millimeter Wave Corneal Reflectometry

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 5 off-axis parabolic mirrors, a thin film beam splitter, and 2-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 beam walk-off.

Design and characterization of a hyperbolic-elliptical lens pair in a rapid beam steering system for THz spectral imaging of the cornea

“…Classification of burn severity is possible by detecting changes in the THz reflectivity, and using machine learning algorithms [7] such as neural networks [8] and support vector machines [9], the wound-healing outcome can be predicted with high accuracy levels. Additionally, THz imaging has been used for diagnosis of brain cancer tumors [10][11][12][13], breast cancer biopsies [14,15], skin cancer delineation [16][17][18] and in several ophthalmological applications [19][20][21][22][23][24][25][26][27][28]. In most of these applications, the only viable imaging modality for clinical applications is spectroscopic imaging in the reflection mode.…”

Accurate and early prediction of the wound healing outcome of burn injuries using the wavelet Shannon entropy of terahertz time-domain waveforms

“…THz-TDS has been effective in the delineation of breast or skin cancer margins, 30 – 36 diagnosis of brain, 37 colon, 38 and gastric tumors, 39 screening diabetic foot syndrome, 40 , 41 and monitoring corneal hydration for diagnosing glaucoma 42 – 49 In skin assessment applications, THz-TDS has been used for quantifying hydration changes in the skin 50 – 55 In addition, the efficacy of theoretical models at describing the interaction of THz radiation with living skin has been explored 56 …”

Accurate and early prediction of the wound healing outcome of burn injuries using the wavelet Shannon entropy of THz time-domain waveforms

“…28,29 THz-TDS has been effective in the delineation of breast or skin cancer margins, [30][31][32][33][34][35][36] diagnosis of brain, 37 colon, 38 and gastric 39 tumors, screening the diabetic foot syndrome 40,41 and monitoring the corneal hydration for diagnosing glaucoma. [42][43][44][45][46][47][48][49] In skin assessment applications, THz-TDS has been used for quantifying the hydration changes in the skin. [50][51][52][53][54][55] In addition, the efficacy of theoretical models at describing the interaction of THz radiation with living skin has been explored.…”