A Kind Of Portable Leaf Area Index Instrument

In ecology,leaf area index is one of the important parameters to reflect the canopy structure of vegetation,which is often used to measure the growth state of vegetation.In modern scientific and technological agricultural production,by measuring and analyzing the changes of leaf area index,we can master the growth status of crops,and provide the basis for the formulation of scientific cultivation technology,so the measurement of leaf area index becomes more and more important.Because the traditional method of measuring leaf area index is destructive to vegetation and its measurement cost is expensive,it usually adopts indirect measurement method based on radiation or hemispherical image,and has been widely recognized and used in scientific research and investigation,among which hemispherical photography is favored by scholars and researchers because of its unique advantages.When the leaf area index is retrieved by hemispherical photography,the effective area of the image is often not in the center of the image.In order to extract canopy porosity from the image,gray and binary image processing are needed.In this paper,a variety of processing methods are compared and the algorithm suitable for this instrument is given.By studying the projection function of vegetation,it is found that different curves will converge near the same value,and the calculation formula of leaf area index is given by using the projection function.In this paper,a leaf area index instrument based on hemispherical photography is studied.It is composed of fish eye lens,optical sensor,microcontroller,memory module and communication module.In essence,it is an image acquisition,storage,transmission and processing system.The instrument obtains the leaf area index by analyzing the canopy image,so the quality of the collected image plays a decisive role in the measurement ability of the leaf area index instrument.This paper takes embedded microprocessor stm32f767 as the core,and completes the hardware circuit design of the instrument.The system is equipped with a 2-megapixel CMOS image sensor ov2640,which can collect hemispherical images that meet the requirements.The microprocessor provides enough computing power.With the software realized by the precision center,the calculation of leaf area index can be completed in real time.In order to work with computer and other host equipment,the system can Communication,USBcommunication interface is added to facilitate the host to control the working state of the instrument.In addition,the memory module of the system can not only store the calculation results,but also save the original image for further analysis.Firstly,this paper introduces the research of hemispherical photography,determines the algorithm flow of inversion of leaf area index of the instrument,then introduces the hardware circuit design,PCB design,software program design and shape structure design of the instrument in detail,and finally proves the basic performance of the instrument through a large number of tests.