Design and evaluation of a long-wave infrared snapshot imaging spectrometer

Long-wave infrared imaging spectrometers are capable of spectrally resolving and spatially imaging the infrared radiation from detected targets. However, achieving high sensitivity poses a significant challenge. This is due to the strong infrared background radiation generated by instruments themselves at ambient temperatures, coupled with the spectral subdivision of the target signal. To address this, we propose an approach that enhances detection sensitivity by increasing signal throughput and incorporating ambient-temperature background suppression. The proposed method replaces the traditional single slit with an aperture-encoding slit array. This increases the incidence flux of target radiation and spatially encodes it. The encoded information, after dispersion and background suppression, is acquired and subsequently decoded via a reconstruction algorithm, enabling snapshot spectral imaging. The prototype covers a spectral range of 7.6-11.35 µm, with a spectral resolution better than 50 nm and a temporal resolution of 10 Hz. This paper details the opto-mechanical design, alignment and testing, and system evaluation. Experimental results demonstrate that the approach achieves fine spectral images of detected targets under ambient opto-mechanical conditions, enabling the detection and identification of dynamic targets. Unlike conventional cooling solutions, the approach avoids the additional weight, volume, and power consumption associated with opto-mechanical cooling. This allows the system to adapt to more lightweight platforms, showing great potential for future applications on unmanned aerial vehicles, as well as airborne and spaceborne platforms.