Dual Imaging Approach Using Laser-Induced Fluorescence and Hyperspectral Reflectance for Automated Sorting of White...

Area of Science:

• Materials Science
• Spectroscopy
• Recycling Technology

Background:

• Automated recycling faces challenges in sorting visually similar materials like polymers, wood, and metals.
• White polyamide polymer is difficult to separate from waste due to its resemblance to wood and metals.

Purpose of the Study:

• To develop and validate a dual imaging approach for accurate discrimination of white polyamide polymer in mixed waste streams.
• To identify optimal spectral bands for distinguishing polymers from wood and metals using fluorescence and reflectance.

Main Methods:

• Combined laser-induced fluorescence (LIF) with ultraviolet excitation and hyperspectral imaging (HSI) of diffuse reflectance (400-1000 nm).
• Analyzed fluorescence emission spectra, particularly in the near-infrared (NIR) region.
• Utilized histogram techniques on HSI data to find optimal wavelengths for contrast enhancement.

Main Results:

• White polyamide showed distinct fluorescence peaks at ~740 nm (NIR) and a secondary peak at 443 nm.
• Significant overlap in fluorescence was observed between wood and polymer in the visible spectrum (480-630 nm).
• Optimal reflectance wavelengths at ~480 nm and 840 nm were identified for improved material contrast.

Conclusions:

• The dual-modality imaging strategy effectively discriminates white polyamide polymer from wood and metals.
• Targeting NIR fluorescence and specific reflectance wavelengths is crucial for accurate sorting.
• This approach supports the development of advanced automated recycling systems and environmental monitoring tools.