基于相位成像的番茄果实糖度检测

Detection of Tomato Fruit Sugar Content Based on Phase Imaging

果蔬品质检测在其生长、储存各环节都具有重要意义,同时也是栽培、保存方案制订的依据。针对果蔬种植过程中对样本全域生理信息定量实时获取的需求以及现有检测技术的不足,本文从宏观生长的微观物质基础和相位成像机理出发,以番茄果实糖度检测为例,提出了一种果蔬生理信息的相位检测方法,基于细胞相位图像提取两个相位参量并联合宏观糖度值构建数据立方体对番茄糖度分布进行了表征。该方法可根据需要对任意局部区域进行采样检测,无须对细胞样本进行预处理,只需要采集任意角度下的一幅相位图即可,具有数据量小、计算简便的优势,整个分析过程只需要0.5 s左右。与现有成熟检测方法的对照实验表明,细胞相位参量与糖度值表现出了明显的正相关性,且对局部糖度差异敏感。所提方法与高光谱成像检测结果具有良好的一致性。该相位检测表征方法操作简便,运算速度快,可为番茄糖度乃至其他果蔬的多种生理特性快速检测提供参考。

Objective Quality testing of tomatoes is critical in many aspects of their growth,storage,and transportation.Sugar content(Brix)is a necessary criterion for evaluating whether a fruit is tasty.The timely and accurate mastery of quality parameters,such as the Brix distribution during the ripening process,is crucial for the scientific and efficient cultivation of tomatoes.Among the widely used detection methods,the Brix meter detection,which is based on the principle of light refraction,is a mean value measurement method based on the fruit juice,which cannot satisfactorily assess the fine distribution of different parts of a sample.The hyperspectral imaging technology leads to a significant amount of redundancy in the amount of data and is easily affected by the depth of light penetration and the water content of the sample,which is insufficient to detect and characterize the full range of details of the sample.Mass spectrometry is complex and cumbersome for sample preparation and does not support rapid detection.This study proposes a method for detecting and characterizing the sugar content of tomato fruits from the perspective of cellular phase information based on phase imaging technology.Methods The physiological properties of the samples were analyzed and characterized in this study from a cellular perspective,starting from the microscopic material basis of plant growth.Based on the characteristics of the quantitative phase microscopy,which uses the inherent contrast source of different refractive indices between different components in the cell,we performed phase imaging experiments on tomato pulp cells and extracted the cellular phase parameters,called phase envelope volume and phase peak.The correlation between the phase parameters and Brix was analyzed by comparing them with the measurement results of the Brix meter.Based on the experimental data,a data cube of the two-phase parameters and Brix was constituted,and positive correlations between the phase parameters and Brix were obtained.This provides a basis for characterizing local Brix using phase parameters.Results and Discussions The proposed detection and characterization method can be applied to any part of a tomato plant and requires only a single frame of the phase map at any incidence angle.The extraction of phase parameters eliminates the tedious operation of decoupling the physical thickness and refractive index of the cells,and the entire analysis process only takes approximately 0.5 s.Based on the sensitivity of the phase information to the internal chemical composition of the cell,the phase parameter characterization method can also be applied to detect the physiological state of other fruits and vegetables in addition to sugar(Fig.10).This study provides a reference for the refinement and precision in detecting the quality of agricultural products.Conclusions This paper focuses on the demand for rapid and accurate quality inspection of fruits and vegetables in modern agriculture.A detection method based on phase imaging is proposed.The inspection of tomato fruit sugar is used as an example to explain the related principles and procedures.In this method,only a single frame of the phase map from any angle of incidence is required.Two phase parameters,that is,phase envelope volume and phase peak,are extracted from the phase map to quantitatively investigate the sugar content characteristic of a cell.The experimental results of the comparison with the detection based on the Brix meter indicate that the sugar content and the above phase parameters show a significant positive correlation.This provides a basis for characterizing the sugar content using the phase parameters.The local sugar content distribution of a tomato fruit was detected experimentally,and the results show good consistency with those of hyperspectral detection.The feasibility and effectiveness of this method have been demonstrated to a certain extent.This phase detection and characterization method requires only one frame of the phase image,and the related analysis process eliminates the cumbersome operation of decoupling the physical thickness and refractive index of the cell.This means that the hardware and time costs can be reduced.Based on the sensitivity of the phase information to the internal chemical composition of the cell,the phase parameter characterization method can also be applied to detect the physiological state of other fruits and vegetables,which may be used as a workable solution for the rapid and accurate detection of agricultural product quality.