An extremely compact and high-speed line-scan hyperspectral imager covering the SWIR range

SWIR (Short Wave Infrared) imaging can be of great use in precision agriculture, food processing and recycling industry, among other fields. However, hyperspectral SWIR cameras are costly and bulky, preventing their widespread deployment on the field. To answer the market need for compact and cost-efficient hyperspectral cameras covering the SWIR range, imec and SCD have joined efforts to develop a novel integration approach combining imec know-how in pixel level patterned thin film spectral filter technology, with SCD's InGaAs technology. The here presented line-scan SWIR hyperspectral camera covers the 1.1-1.65 μm range with 100+ bands and a spectral resolution better than 10 nm. This imager uses a set of patterned Fabry-Pérot interferometers processed using semiconductor grade thin-film technology. The optical filters are then integrated directly on top of the sensing side of the InGaAs detector with high accuracy and with a minimum gap between filters and Focal Plane Array to limit cross-talk. The resulting line-scan camera, measuring only 70x62x60 mm and with a weight below 0.5kg, is the lightest and most compact SWIR hyperspectral camera on the market. Full sensor readout can be performed at up to 350 fps. An imecpatented SnapScan system with internal scanning was also developed, capable of acquiring data cubes of 640x512x128 pixels in a second. Maximum cube size is 1200x640x128. By selecting a subset of contiguous spectral bands and a reduced spatial resolution the sensor could be operated @ +1000 fps, for example enabling cube acquisitions of 320x512x64 in less than 300 ms.