MEMS for multispectral imaging

The anticipated feature of future generation remote infrared (IR) sensing and imaging technologies includes adding so-called multi-colour capabilities. Such enhancement of the current state-of-the-art IR detector and imaging focal plane array (FPA) technologies allows real-time spectral information to be gathered from multiple wavelength bands. Multi/hyper-spectral imaging results in improved target recognition and is applicable to numerous remote sensing spectroscopy/imaging applications. In order to provide a reduced size, weight and power (SWaP) solution, a microelectromechanical systems (MEMS) based electrically tuneable adaptive filter technology has been developed for important IR bands of the electromagnetic spectrum. The adopted approach is capable of delivering on-chip remote hyper/multi-spectral sensing by obtaining narrow-band spectral sensitivity utilising a tuneable MEMS optical filter fabricated directly on a detector. This paper summarizes the performance demonstrated within the most technologically relevant bands of short-wave IR (SWIR, 1.4-2.5 µm), mid-wave IR (MWIR, 3-5 µm), and long-wave IR (LWIR, 8-12 µm). In SWIR, the demonstrated nanometer-scale uniformity in the flatness of suspended MEMS allows for spatial uniformity of the filtered peak centre wavelength and the achieved 30-35 nm spectral width to remain within single nanometers over 500µm x 500µm optical apertures. In LWIR, the spatial peak wavelength selectivity variation is achieved to be less than 1.2% across 200μm × 200μm optical imaging areas, exceeding the requirements for passive multispectral thermal imaging and validating the suitability for mechanically robust multi/hyper-spectral remote sensing and imaging applications deployable on low-SWaP field-portable platforms.