Fig. 1. Near-infrared diffuse reflection on-line detecting device
1: Light source; 2: Light source receiving port; 3: Light source transmitting and receiving port; 4: QE PRO spectrometer; 5: Computer; 6: Navel orange sample; 7: Fruit cup

Fig. 2. Near-infrared diffuse transmission on-line detecting device
1: Light source; 2: Sample; 3: Shading ring; 4: Optical path; 5: Fiber optic probe; 6: Bouncing claw

Fig. 3. Schematic diagrams of light paths of diffuse transmission (a) and diffuse reflection (b) for large and small navel oranges

Fig. 4. Spectral comparison of fruit with different sizes using three detection methods

Fig. 5. Scatter plot of dimensional model prediction results under different detection modes
(a): Diffuse transmission detection method size prediction scatter plot; (b): Multi-point transmit and receive diffuse reflection detection method size prediction scattered points; (c): Circular emission and reception diffuse reflection detection method size prediction scatter plot

Fig. 6. Diffuse transmission MSC-PLS modeling scatter plot

Fig. 7. Comparison of regression coefficient and diffuse transmission size

Table 1. Statistical results of physical and chemical indicators of navel orange

Table 2. PLS modeling prediction results for different size sample sets by using different detection methods