Optimizing illumination for mid-wave infrared hyperspectral imaging in black plastic recycling

Sorting black plastics is challenging due to their strongnabsorption in the visible and short-wave infrared ranges inducednby added carbon black particles as colorant. Conventional sortingnmethods struggle due to too low reflectivities. Mid-wave Infraredn(MWIR) hyperspectral imaging offers a possible solution,nproviding sufficient signal level for classification. In this work,nthe illumination of the Specim FX50 MWIR hyperspectral cameranwas optimized by the developmentof a line-focused illuminationnsystem using quartz tube heaters and elliptical reflectors.nThe new setup improved signal-to-noise ratios, eliminated temporalndrifts, and allowed successful classification of black plasticsn(HDPE, ABS and PP). However, sensitivity to ambient temperaturenvariations highlights the need for a temperature stabilizednenvironment to achieve reproducible results and enable reliablenoperation in industry.