Freeform based hYperspectral imager for MOisture Sensing (FYMOS)

Area of Science:

• Optical Engineering
• Remote Sensing
• Spectroscopy

Background:

• Accurate remote moisture sensing is crucial for environmental monitoring and resource management.
• Existing hyperspectral imaging systems often face limitations in weight, size, and optical performance.

Purpose of the Study:

• To introduce FYMOS, a novel all-aluminum, freeform-based near-infrared hyperspectral imager designed for robust and lightweight moisture sensing.
• To evaluate the optical performance and demonstrate the moisture measurement capabilities of the FYMOS system.

Main Methods:

• Designed and constructed FYMOS, integrating an InGaAs sensor for spectral features from 0.7-1.7µm.
• Utilized a three-concentric-mirror (Offner) spectrograph configuration with a bespoke freeform blazed grating.
• Achieved improved RMS wavefront error through freeform optics and a monolithic mirror design.
• Measured water evaporation rates on a soil sample and processed data with the MARMIT radiative transfer model.

Main Results:

• FYMOS offers a spectral resolution of 8 nm, optimized for broad spectral coverage and water level assessment.
• A 30% improvement in RMS wavefront error was achieved compared to conventional designs.
• The system demonstrated effective remote measurement of moisture content, estimating mean water thickness from soil evaporation data.

Conclusions:

• FYMOS represents a significant advancement in hyperspectral imaging for moisture sensing, offering superior optical performance in a compact and lightweight package.
• The system's ability to accurately estimate water thickness using spectral data and radiative transfer models highlights its potential for various environmental applications.