Cielecki Paweł Piotr, Hardenberg Michel, Amariei Georgiana, Henriksen Martin Lahn, Hinge Mogens, Klarskov Pernille
Terahertz Photonics, Department of Electrical and Computer Engineering, Aarhus University, Finlandsgade 22, 8200, Aarhus N, Denmark.
Plastic and Polymer Engineering, Department of Biological and Chemical Engineering, Aarhus University, Aabogade 40, 8200, Aarhus N, Denmark.
Sci Rep. 2023 Dec 16;13(1):22399. doi: 10.1038/s41598-023-49765-z.
Several optical spectroscopy and imaging techniques have already proven their ability to identify different plastic types found in household waste. However, most common optical techniques feasible for plastic sorting, struggle to measure black plastic objects due to the high absorption at visible and near-infrared wavelengths. In this study, 12 black samples of nine different materials have been characterized with Fourier-transform infrared spectroscopy (FTIR), hyperspectral imaging, and terahertz time-domain spectroscopy (THz-TDS). While FTIR validated the plastic types of the samples, the hyperspectral camera using visible and near-infrared wavelengths was challenged to measure the samples. The THz-TDS technique was successfully able to measure the samples without direct sample contact under ambient conditions. From the recorded terahertz waveforms the refractive index and absorption coefficient are extracted for all samples in the range from 0.4 to 1.0 THz. Subsequently, the obtained values were projected onto a two-dimensional map to discriminate the materials using the classifiers k-Nearest Neighbours, Bayes, and Support Vector Machines. A classification accuracy equal to unity was obtained, which proves the ability of THz-TDS to discriminate common black plastics.
几种光学光谱和成像技术已经证明了它们识别家庭垃圾中不同塑料类型的能力。然而，大多数适用于塑料分类的常见光学技术，由于在可见光和近红外波长下的高吸收率，难以测量黑色塑料制品。在本研究中，使用傅里叶变换红外光谱（FTIR）、高光谱成像和太赫兹时域光谱（THz-TDS）对九种不同材料的12个黑色样品进行了表征。虽然FTIR验证了样品的塑料类型，但使用可见光和近红外波长的高光谱相机在测量样品时遇到了挑战。THz-TDS技术成功地在环境条件下无需直接接触样品就能测量样品。从记录的太赫兹波形中提取了所有样品在0.4至1.0太赫兹范围内的折射率和吸收系数。随后，将获得的值投影到二维图上，使用k近邻、贝叶斯和支持向量机分类器来区分材料。获得了等于1的分类准确率，这证明了THz-TDS区分常见黑色塑料的能力。
