基于叶片含水量的激光偏振成像模型研究

Laser polarization imaging models based on leaf moisture content

目标物体的偏振特性是一种固有特性,由目标的外部结构、内部结构以及入射角度等决定,因此利用偏振信息研究植物叶片含水量测量。主要研究过程分为以下五个部分:搭建激光偏振成像测量实验系统、计算目标偏振度、测量叶片实际含水量、建立偏振度与叶片含水量间映射模型、验证映射模型。根据目标与环境特性,选择和调整实验器件和实验步骤;基于图像灰度提取方法计算目标偏振度;采用水分梯度处理方法测量叶片实际含水量;基于统计方法建立叶片偏振度与含水量的一到三阶函数映射模型,比较一到三阶模型的稳定性与预测能力分析其适用情况,为利用偏振测定植物叶片含水量的方面提供理论基础。结果发现:在含水量所处15%~75%区间内,偏振度随着水分含量上升呈现一个递增趋势。含水量较高情况下,递增关系较明显;含水量较小情况下,映射关系不显著。

The polarization characteristic of objects is an inherent characteristic, depending on the external and internal structure of targets as well as the incident angle. Therefore, the measurement of leaf moisture content was researched with polarization information. The research process was divided into the following five parts： Establishing the laser polarization imaging measurement system, calculating the polarization degree of targets, measuring the actual moisture content of leaf, establishing a mapping model between polarization degree and leaf moisture content, and validating the mapping model. According to the target and environment characteristics, the devices and steps of experiment can be chosen and adjusted. The polarization degree can be measured by the method of extracting grey-scale value of the image. Moisture gradient processing was used to measure the actual moisture content of leaf. The mapping models between polarization degree and leaf moisture content were established in the first to third orders based on statistical method. Their stabilities and predictive abilities were compared to analyze their applicable conditions, which provide a theoretic foundation of leaf moisture content measurement with polarization information. The result shows that the polarization degree increases progressively with the moisturecontent rising from 15% to 75%. The mapping relationship was obvious in case of the high moisture content, while it was insignificant in case of the low moisture content.