Multispectral imaging has been studied in recent years as a means of assessing fruit firmness. Here we report on the development of a static multispectral imaging system (MSI) that was used to validate the potential of the technique for high-speed commercial grading. The system consists of a high-performance CMOS camera, four lasers, electronically controlled shutters and a location control system. It captures four spectral scattering images on the fruit. In this study 100 ‘Royal Gala’ apples have been measured using the static MSI. The MSI measurements were applied on the intact apple and also on a flat surface of internal flesh exposed by removing a thick skin slice. The scattering profiles were fitted with a standard light diffusion model and a heuristic modified Lorentzian model. The results showed that the correlations between penetrometer firmness and model parameters were poor, with the correlation coefficient, R, ranging from 0.4 to 0.8 in the best circumstance of the flat surface measurements. Although multivariate models can improve the correlations, this work suggests that laser scattering information on its own is not sufficient to predict the firmness.
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机译：近年来，已经对多光谱成像进行了研究，以评估水果的硬度。在这里，我们报告静态多光谱成像系统（MSI）的开发，该系统用于验证该技术在高速商业分级中的潜力。该系统由高性能CMOS相机，四个激光器，电子控制的百叶窗和位置控制系统组成。它捕获水果上的四个光谱散射图像。在这项研究中，使用静态MSI测量了100个“ Royal Gala”苹果。 MSI测量适用于完整的苹果以及通过去除厚皮片而暴露的内部果肉的平坦表面。散射轮廓符合标准的光扩散模型和启发式修改的洛伦兹模型。结果表明，在最佳的平面测量情况下，针入度计的硬度与模型参数之间的相关性较差，相关系数R在0.4至0.8的范围内。尽管多元模型可以改善相关性，但这项工作表明，仅靠激光散射信息不足以预测硬度。
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