温室作物长势的光谱学诊断方法研究与仪器开发

利用便携式光谱辐射仪测量了温室栽培黄瓜叶片的光谱反射率，相关分析结果表明：527 和762 nm是可用来预测叶片氮素含量的敏感波长。利用敏感波长处的反射率，生成了归一化颜色指数(NDCI)，并建立了基于NDCI的黄瓜叶片氮素含量预测模型，模型的相关系数达到了0.881。在上述研究的基础上，开发了一种基于光导纤维的便携式作物长势诊断仪。仪器主要包括四个部分：反射光采集系统、测光单元、信号调理电路和数据采集系统。从作物表面反射的自然光经过光纤传输至光电转换单元，经滤光后得到所需要的敏感波长，光电器件将光信号转变为电信号，然后根据预测模型判别作物的生长状态。标定试验结果表明，仪器所测的光谱数据与作物叶绿素含量之间存在显著的线性关系。

New Method and Instrument to Diagnose Crop Growth Status in Greenhouse Based on Spectroscopy

Spectral reflectance of cucumber leaves in greenhouse was measured using an ASD FieldSpec Pro VNIR spectrometer with natural illumination. Two sensitive wavelengths, 527nm and 762 nm, were selected to evaluate the nitrogen content of the cucumber leaves. A model was established and validated using normal difference color index(NDCI) with the correlation coefficient of 0.881. Based on the above efforts, a handheld spectral instrument was developed to diagnose the growth status of the crop in greenhouse using fiber optics. The instrument was mainly composed of four parts: reflected light acquisition system, light intensity measurement unit, signal conditioning unit, and data acquisition system. The sunlight reflected by the crop was transmitted by the fiber, and passed through the light filter to obtain light at the sensitive wavelengths. Finally it was transformed into electronic signal by the photoelectric transistor, and was used to diagnose the growth status of the crop according to the evaluation model. The result showed that the developed instrument was practical.