基于近红外反射的柑橘重叠叶片叶面积指数测量系统

Measurement System for Citrus LAI Based on Near-infrared Reflection

摘要:

提出一种基于近红外反射的柑橘叶面积指数（LAI）测量方法。在平直近红外激光照射下，光电探测器接收重叠叶片的反射光能量，通过数据采集卡采集电压信号至上位机，利用LabVIEW软件编程，自动判断出重叠叶片层数。将叶片层数乘以直射光束的光斑面积即为该测试位置叶面积，而每次测试的叶面积累加即为该测试区域的总叶面积，最终求出LAI。根据光谱反射试验结果选用近红外作为光源进行系统标定，得到重叠叶片层数与测量电压的指数拟合模型，Ssig<0.05水平显著。试验结果表明，在手动扫描、定时采集方式下，以方格法计算的LAI作为真实值，系统对LAI的计算误差为11.01%。

Abstract:

In order to construct a fast measurement system for leaf area index (LAI) based on near-infrared reflection, an innovative way was explored to accurately detect the LAI of overlapping leaves. Research methods were concluded as follows: overlapping leaves were put under the direct parallel light generated by the near-infrared laser, and the photoelectric sensors were used to measure the reflected light energy. The output voltage signal of the sensors was sent into the computer through the data acquisition card. The amount of overlapping layers was determined by software programming. The amount of overlapping layers was multiplied by the area of direct beam’s light spot was the area of the leaves. The total area of the leaves was the cumulative leaf area in the whole testing process and LAI could be calculated. Based on the result of spectral reflection test, near-infrared was used as direct light source to demarcate the system to get the index fitting model between overlapping leaves’number and measuring voltage, which is notable in 0.05 statistic level. The result of data collection experiment shows that under the method in manual scanning and timing collection, the value of LAI was calculated by the system with 11.01% of the error compared with the true value of LAI calculated by square method.