Compact high-speed snapshot hyperspectral imager in the SWIR range (1.1-1.65 nm) and its potential in sorting/recycling industry

Abstract

This paper presents the latest Imec snapshot hyperspectral imager based on either 3x3 or 4x4 mosaic filter patterning on an industry-ready SWIR detector. The mosaic patterns are implemented by means of high-transmission Fabry-Perot interferometers processed using thin-film technology. Our snapshot hyperspectral imager offers a spatial resolution of 640x512 pixels down sampled according to the mosaic pattern to acquire data in 9 (3x3), or 16 spectral bands (4x4) in the 1100-1650nm range. To achieve imaging at the native spatial resolution of the sensor, super resolution methods are available post-acquisition. Moreover, this compact USB-3 camera of 65x65x130 cm and 260 gr (without lens) reaches an acquisition speed of up to 120 hyperspectral cubes/second, and it is therefore suitable for high-speed inspection such as a conveyor belt. Its potential on the sorting and recycling industry is showcased for three applications: plastic recycling application, textile sorting and discrimination of a mixed plastic and textile materials. The first application focuses on sorting of plastic (HDPE, PET, PP) and paper (cardboard, paper, newsprint, tetra Pak). The second application focuses on discrimination of textiles such as cotton, PET, wool, silk, polyamide, and blends of these ones. The last application aims at discriminating a new sample set of the previous categories of plastic and textiles. A pixel-accuracy over 90% is obtained for each sample set with close to 100% object-level discrimination. This shows the high potential of SWIR range snapshot hyperspectral imagers for sorting/recycling and, by extension, for many other applications.