Development Of A Chlorophyll Fluorescence Imaging System Based On A Micro CMOS Camera

Chlorophyll fluorescence is closely coupled with the photochemical reaction process.Chlorophyll fluorescence imaging,which is frequently utilized in various fields including plant physiology research and smart agricultural information perception,has developed into an effective method of getting information about plant photosynthesis and physiological state.The application of chlorophyll fluorescence imager is challenging due to its high cost and complex structure.In order to address the aforementioned issues,this paper investigates and constructs a low-cost chlorophyll fluorescence imager based on a micro CMOS camera and a smartphone,and carries out experimental verifications and applications on it.The main research results are as follows:(1)Study on the light path of the chlorophyll fluorescence imager.The excitation light group adopts a PWM control scheme and an LED surface light source with a bowl-shaped structure.The distribution characteristics of the light field are analyzed by simulation analysis.After the calibration,the theoretical light intensity can reach 6250?mol/m~2/s,and the uniformity deviation of the light field is about 2%.Finally,the feasibility of the excitation light and photosensitive imaging is demonstrated through the calculation and analysis of the fluorescence imaging intensity of the CMOS camera.(2)System design and development of chlorophyll fluorescence imager.The overall design and development of the fluorescence instrument is completed from the mechanical structure,hardware circuit and system software of the fluorescence instrument.Through the design of the cabinet with the lifting platform,the maximum volume is 30cm×30cm×25cm;the smartphone is used as the upper computer to complete the excitation light control,and the data is sent back to the smartphone or server for analysis,processing,storage and display.The fluorescence instrument can realize image acquisition of 5 million pixels,spectral range 400-1000nm,90fps,and has continuous light excitation and modulated pulse excitation functions.(3)Basic experimental testing of the chlorophyll fluorescence imager.The measured excitation light intensity of the chlorophyll fluorescence imager is 5956?mol/m~2/s,and the uniformity deviation is about 2.3%.The measured data is consistent with the theoretical analysis and simulation,which can meet the requirements of fluorescence detection.The instrument is capable of collecting images of chlorophyll fluorescence under continuous light excitation or the protocol of modulated pulsed light.The acquired chlorophyll fluorescence image can reflect the two-dimensional heterogeneity of leaves and can effectively distinguish the photosynthetic characteristics of different leaves.Typical The chlorophyll fluorescence parameter images of F_v/F_m,Rfd,etc.are in line with expectations.(4)Research on the influence of leaf angle and leaf age on chlorophyll fluorescence imaging based on chlorophyll fluorescence imager.Aiming at the mechanism of large-scale sunlight-induced chlorophyll fluorescence detachment from microscopic chlorophyll imaging,a total of 60 leaves of plants representing vines,trees and shrubs,namely,epipremnum aureum,camphor tree and Euonymus chinensis,were used as samples to explore the chlorophyll fluorescence imaging and imaging angles.Links exist between leaf age.The experimental results show that the imaging angle has a significant impact on the chlorophyll fluorescence imaging,and the increase of the imaging angle will lead to the decrease of the fluorescence parameter value,and the influence on different plants species varies.Chlorophyll fluorescence imaging is influenced by leaf age as well,with growing leaves having greater imaging parameters than mature leaves.This result is of great significance for the mechanism research of chlorophyll fluorescence remote sensing imaging.The research and development results of this paper have effectively realized the low-cost design of the chlorophyll fluorescence imager,which is conducive to the rapid qualitative analysis of chlorophyll fluorescence images and lays the foundation for accurately playing the role of chlorophyll fluorescence in the evaluation and decision-making of smart agriculture.