Opt Lett. 2021 Mar 1;46(5):1065-1068. doi: 10.1364/OL.419140.
Topographical abnormality in corneal tissue is a common diagnostic marker for many eye diseases and injuries. Using an asynchronous optical sampling terahertz time-domain spectroscopy setup, we developed a non-contact and normal-incidence imaging system to measure topographic changes along the surface of spherical samples. We obtained orthogonal 1D scans of calibration spheres to evaluate the minimum axial resolution of our system. We determined the axial and spatial resolution of the scanner using 3D-printed spherical cross and Boehler star targets. Furthermore, we characterized the asymmetrical performance of the scanner due to the use of an off-axis parabolic mirror. Finally, we developed an edge-detection filter to aid with improving the topographic scans. We showed that when imaging samples were comparable in size to the human cornea, the axial and spherical spatial resolutions were limited to about 15 µm (∼/67) and 1 mm, respectively.
角膜组织的地形异常是许多眼病和损伤的常见诊断标志物。我们使用异步光学采样太赫兹时域光谱装置，开发了一种非接触式和正入射成像系统，以测量球形样品表面的地形变化。我们对校准球进行了正交 1D 扫描，以评估我们系统的最小轴向分辨率。我们使用 3D 打印的球形十字和 Bohler 星目标确定了扫描仪的轴向和空间分辨率。此外，我们还由于使用了离轴抛物面镜，对扫描仪的不对称性能进行了特征描述。最后，我们开发了边缘检测滤波器，以帮助改善地形扫描。我们表明，当成像样品的尺寸与人类角膜相当时，轴向和球空间分辨率分别限制在约 15μm（∼/67）和 1mm 左右。
