Fig. 1. Laser Raman microplastic measuring system
1: Excitation light source; 2: Incident optical fiber; 3: Probe; 4: Simple; 5: Receiving optical fiber; 6: Spectral collection module; 7: Spectral processing module; 8: Photoelectric conversion module; 9: Data processing module

Fig. 2. Original Raman spectra of polypropylene (a) and Raman spectra after pretreatment (b)

Fig. 3. Flow chart of data processing module

Fig. 4. CV accuracy of decision tree (DT) and random forest (RF) with different spectral points number

Fig. 5. CV accuracy of decision tree (DT) and random forest (RF) with different k values

Fig. 6. Operation results of decision tree (DT) and random forest (RF)