The design, simulation, and characterization of a quasioptical system for submillimeter-wave quantification of corneal thickness and water content are presented. The optics operate in the 220–330 GHz band and are comprised of two, custom aspheric, biconvex lenses in a Gaussian beam telescope configuration. The design produces broadband wavefront curvature matching to 7.5 mm radius of curvature target surfaces thus emulating a plane-wave-on-planar-media condition and enabling application of stratified medium theory to data analysis. Aspheric lens coefficients were optimized with geometric ray tracing subject to optical path length penalties and physical-optics simulations showed aspheric designs achieved wavefront coupling to spherical surfaces, superior to equivalent, canonical hyperbolic lenses. The fabricated lens system was characterized in a planar near-field scanner system and demonstrated good agreement to physical-optics simulations. An average central corneal thickness of 652 μ m and free water content volume of 47% were extracted from ex vivo sheep corneas via complex s -parameters and agree with literature values. Extracted contact lens thickness and water content agreed with independently validated values. Moreover, the quasioptical system enabled observation of dynamic changes in artificial tear-film, thickness, and water content. This work elucidates two major findings related to submillimeter-wave wavefront matching on spherical surfaces, with wavelength order radii of curvature: 1) An asphere whose sag coefficients are optimized via field phase variation on a spherical surface produces coupling superior to a plano-hyperbolic lens. 2) For most feasible apertures, the Gaussian beam waist is located in the aperture near field, suggesting consideration for operating in the beam near field.

中文翻译：

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用于220-330 GHz角膜传感的准光学系统：设计，评估和 离体 角膜参数提取

介绍了准毫米波系统用于角膜厚度和水含量亚毫米波量化的设计，仿真和表征。光学器件工作在220–330 GHz频段，由两个高斯光束望远镜配置的定制非球面双凸透镜组成。该设计可产生与7.5 mm曲率半径目标表面匹配的宽带波前曲率，从而模拟平面介质上的平面波条件，并使分层介质理论能够应用于数据分析。非球面透镜系数通过几何光线跟踪进行了优化，受到光程长度的影响，物理光学仿真显示，非球面设计实现了波前耦合到球面的波前耦合，优于等效的经典双曲透镜。所制造的透镜系统在平面近场扫描仪系统中得到了表征，并证明与物理光学仿真具有良好的一致性。角膜中央平均厚度为652μ 从中提取m和47％的自由水含量 离体 通过复杂的羊角膜 s -参数并与文献数据一致。提取的隐形眼镜厚度和水含量与独立验证的值一致。此外，准光学系统能够观察人造泪膜，厚度和水含量的动态变化。这项工作阐明了与球面亚毫米波波阵面匹配有关的两个主要发现，其波长阶曲半径为：1）通过在球面上通过场相位变化优化了垂度系数的非球面产生的耦合优于平面双曲透镜。2）对于大多数可行的光圈，高斯光束束腰位于近场光圈中，建议考虑在近场光束中进行操作。