A compact and rugged hyperspectral camera for remote sensing based on FT spectroscopy

Spectral imaging is a method to acquire the spectrum of the light for each point in the image of a scene. By combining classical imaging with Fourier-Transform spectrometry it is possible to acquire hyperspectral images with higher spectral accuracy and lower times compared to standard dispersive optical systems. The technique is based on interferometry, and is hence technically challenging as it requires to generate field replicas with delay controlled within a small fraction (1/100 or better) of the optical cycle. Standard FT spectrometers are heavy, cumbersome and too sensitive to mechanical and thermal perturbations for use in portable devices or for deployment in space applications. Here we propose and experimentally validate a compact FT-based hyperspectral camera, in which the FT module is an innovative ultra-stable birefringent common-path interferometer (the Translating-Wedge-Based Identical Pulses eNcoding System, TWINS). TWINS has intrinsic interferometric stability, it is lightweight and is ultracompact, making our FT-based hyperspectral camera an ideal device for portable on-field and spaceborne applications. Our prototype camera is able to measure absolute reflectance and fluorescence with very high spectral accuracy in the visible and nearinfrared spectral range and can be extended to the spectroscopically rich thermal infrared range (3-14 μm) using suitable birefringent materials and detectors. We present some examples of application in the visible and TIR ranges.