Freeform based hYperspectral imager for MOisture Sensing (FYMOS)
Freeform based hYperspectral imager for MOisture Sensing (FYMOS)
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DOI：
10.1364/oe.425660
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发表时间：
2021-05-24
期刊：
影响因子：
3.8
通讯作者：
Bourgenot, Cyril
中科院分区：
文献类型：
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作者：
Graham, Christopher;Girkin, John M.;Bourgenot, Cyril
我们推出 FYMOS，这是一款全铝、坚固、重量轻、基于自由形状的近红外高光谱成像仪，用于湿度传感。 FYMOS 的设计和制造旨在利用 0.7-1.7 μm 的光谱特征，集成 InGaAs 传感器来远程测量水分含量。该成像系统以 F/2.8 运行，基于三同心镜 (Offner) 光谱仪配置，提供 8 nm 的光谱分辨率，针对宽光谱覆盖范围进行了优化，并具有足够的分辨率来评估水位。为了优化光学性能，同时最大限度地减少重量和尺寸，该设计采用了在商用 5 轴超精密金刚石机床上加工的定制自由形状闪耀光栅。与具有相似孔径的传统 Offner-Chrisp 设计相比，我们在空间和光谱场中的 RMS 波前误差提高了 30%，并且单片主/三级镜简化了制造组装，同时最大限度地减少了重量。我们通过测量土壤样本上水的蒸发率来展示 FYMOS 的性能，并使用物理多层辐射传输模型 (MARMIT) 处理结果以估计平均水厚度。由光学协会根据知识共享署名 4.0 许可条款发布。
We present FYMOS, an all-aluminum, robust, light weight, freeform based, near infrared hYperspectral imager for MOisture Sensing. FYMOS was designed and built to remotely measure moisture content using spectral features from 0.7-1.7 mu m integrating an InGaAs sensor. The imaging system, operating at F/2.8, is based on the three-concentric-mirror (Offner) spectrograph configuration providing a spectral resolution of 8 nm optimized for broad spectral coverage with sufficient resolution to make assessments of water levels. To optimize the optical performance, whilst minimizing weight and size, the design incorporates a bespoke freeform blazed grating machined on a commercial 5 axis ultra precision diamond machine. We achieve a 30% improvement on the RMS wavefront error in the spatial and spectral fields compared to a conventional Offner-Chrisp design with similar aperture and the monolithic Primary/Tertiary mirror eases the manufacturing assembly whilst minimizing weight. We demonstrate the performance of FYMOS by measuring the evaporation rate of water on a soil sample and results are processed with a physical multilayer radiative transfer model (MARMIT) to estimate the mean water thickness. Published by The Optical Society under the terms of the Creative Commons Attribution 4.0 License.