Fig. 1. The handheld multispectral imaging system (a), the layout of LEDs (b), the central wavelength of each LED (c), the software (d) and the in-house hyperspectral imaging system (e)

Fig. 2. The mean spectral reflectance measured by the indoor hyperspectral imaging system (a) and the handheld multispectral imaging system (b), the original hyperspectral reflectance and reconstructed hyperspectral reflectance (c), the correlation coefficient between the original hyperspectral reflectance and reconstructed hyperspectral reflectance (d)

Fig. 3. The performance of PLSR model based on spectral reflectance at 225 wavelengths in visible range measured by the indoor hyperspectral imaging system (a) and the spectral reflectance at four wavelengths in visible range measured by the handheld multispectral imaging system (b)

Fig. 4. The impact of different numbers of standard samples on the predicting ability of PLSR model (a) and the performance of PLSR model based on the reconstructed hyperspectra using 5 standard samples (b)