研究目的
To retrieve the absorption and reduced scattering coefficients of whole apples with complex shapes and investigate the effect of local boundary curvature on these optical properties, as well as establish a relationship between optical properties and apple firmness.
研究成果
The study confirms that boundary curvature affects the retrieval of optical properties, with absorption coefficients overestimated on high-curvature areas, while reduced scattering coefficients are less influenced. A negative correlation exists between reduced scattering coefficient and apple firmness, demonstrating the potential of spatially-resolved imaging for non-destructive quality assessment. Future work could involve multi-wavelength measurements to improve correlations.
研究不足
The method is sensitive to the flatness of the sensing boundary due to the use of a semi-infinite diffusion model, and local curvature can lead to overestimation of absorption coefficients. The technique may be influenced by skin thickness and pigment spots, and requires optimal sensing ranges to balance signal-to-noise ratio and curvature effects.
1：Experimental Design and Method Selection:
The study used Monte Carlo simulations for numerical analysis and an experimental setup with a steady-state imaging system for measurements. The diffusion theory model was applied for inverse algorithm fitting of optical properties.
2：Sample Selection and Data Sources:
207 'Royal Gala' apple cultivars were used, with seven for curvature effect analysis and 200 for firmness correlation. Apples were selected based on homogeneous coloring, mass, and size, stored at 4°C and stabilized at room temperature before experiments.
3：List of Experimental Equipment and Materials:
He-Ne laser (633 nm, 35 mW), CCD camera (Model C4880-21-24A, Hamamatsu Photonics), goniometer system, traction machine (MTS Synergie 200H) for firmness measurement, and apple samples.
4：Experimental Procedures and Operational Workflow:
For simulations, Monte Carlo code was used with 2x10^6 photons to model light propagation in a spheroid apple model. For experiments, apples were rotated manually at angles φ and θ, with laser beam normal to the surface, and backscattered images were captured. Optical properties were retrieved using an inverse algorithm in Matlab, fitting profiles in the range 2.8-10 mm. Firmness was measured destructively using a penetrometer.
5：8-10 mm. Firmness was measured destructively using a penetrometer.
Data Analysis Methods:
5. Data Analysis Methods: Nonlinear least squares curve fitting in Matlab 8.a for optical properties retrieval, and Partial Least Squares (PLS) regression for firmness prediction models, with cross-validation and statistical analysis of correlations.
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