基于等离子体三维成像技术的柑橘中黄龙病斑纹识别方法研究

A Study on A Recognition Method for Huanglongbing in Citrus Based on Plasma Three-Dimensional Imaging Technology

【目的】黄龙病是柑橘植被生长过程中由细菌引起的一种病变,严重影响着柑橘的食用品质,且传染性较大。激光诱导击穿光谱技术是一种多元素检测和分析的有效手段。基于等离子体反演的三维图像中富含大量的元素信息,可以为柑橘中黄龙病斑纹的识别提供依据。【方法】以等离子体光学检测技术为背景,着重研究了局部热平衡条件下的等离子体三维成像及平均贡献率物理模型,构建了柑橘果皮表面黄龙病斑纹的识别系统。在被激发的等离子体复合系统中,结合光谱线强度信息,以K元素为内标元素分析了其余元素在测量区域内的含量。借助激光诱导击穿光谱技术,采集了不同延迟时间的等离子体三维图像。根据量子力学理论中微观粒子运动形式的不连续性提取了平均贡献率。将Ca元素作为分析参量,计算了在等离子体三维空间中的平均贡献率值,对识别方法进行了验证和分析。【结果】在各延迟时间点处,根据内标法和采集三维图像可知果皮表面等离子体信号存在明显的不同。与原始光谱数据相比,等离子体三维成像的差异更加鲜明,信号对比也更加突出。在各采集点处,黄龙病果皮中Ca元素的平均贡献率都明显大于健康果皮,并且在等离子体能量最大时差异最大。【结论】黄龙病等离子体在前期发射强度大于健康果皮等离子体发射强度,同时等离子体寿命更长,相比于健康柑橘更晚开始坍缩消失。利用等离子体三维成像技术可以精确地对感染黄龙病的柑橘进行识别,并且在等离子体能量最强时效果最佳,这一特征可以为最佳等离子体信号的采集提供依据。

[Objective]Huanglongbing is a disease caused by bacteria during the growth of citrus vegetation,which seriously affects the eating quality of citrus and is highly infectious.Laser induced breakdown spectroscopy(LIBS)is an effective method for multi-element detection and analysis.The three-dimensional image based on plasma inversion is rich in element information,which can provide a basis for the identification of Huanglongbing in citrus.[Method]Based on the plasma optical detection technology,the three-dimensional imaging of plasma and the physical model of average contribution rate under the condition of local heat balance were studied,and a recognition system of Huanglongbing spot on the surface of citrus peel was constructed.In the excited plasma recombination system,combined with the spectral line intensity information,the contents of other elements in the measurement area were analyzed with K element as the internal standard element.With the help of laser-induced breakdown spectroscopy,three-dimensional images of plasma with different delay times were collected.According to the discontinuity of micro particle motion in the quantum mechanics theory,the average contribution rate was extracted.Taking Ca element as the analysis parameter,the average contribution rate of plasma in the three-dimensional space was calculated,and the identification method was verified and analyzed.[Result]At each delay time point,according to the internal standard method and the acquisition of three-dimensional images,the plasma signals on the peel surface were obviously different.Compared with the original spectral data,the difference in the plasma three-dimensional imaging is more distinct,and the signal contrast was more prominent.The average contribution rate of Ca in Huanglongbing pericarp was significantly higher than that in healthy pericarp,and the difference was the largest when the plasma energy was the largest.[Conclusion]The results showed that the plasma emission intensity of Huanglongbing was higher than that of healthy peel in the early stage,and the plasma lifetime was longer.Compared with healthy citrus,Huanglongbing began to collapse later.The three-dimensional imaging technology of plasma can accurately identify the citrus infected with Huanglongbing,and the effect is the best when the plasma energy is the strongest.This feature can provide the basis for the collection of the best plasma signal.