Study On The Chlorophyll Meter Based On RGB Color Sensor

Precision agriculture is a kind of advanced farming method, which is based on the status of crop growth and the environment. The first step of precision agriculture is to obtain information on crop. Leaf chlorophyll measurements can guide the application of nitrogen and provide a scientific basis for the study of plant physiological characteristics, tap production potential and variety of resources. In this paper, the design of a chlorophyll meter is presented. This meter has a RGB color sensor as the core device. This meter is different from the existing chlorophyll meter in principle, mainly reflected in: the existing meter such as SPAD502 has a 652nm-wavelength LED as light source, while chlorophyll meter presented by this paper used a super-bright white LED as it light source. Spectrum of this white LED is across the entire visible light spectrum. This paper included several aspects below:1. Introduced the concept of precision agriculture, the importance of the measurement of chlorophyll in agricultural production and three methods to measure the content of leaf chlorophyll: spectrophotometer method, computer vision method, and chlorophyll measurement method. Proposed to use optoelectronic devices to design a small portable chlorophyll meter.2. As to the color-analysis, this paper, introduce the basic information of RGB color space, HSI color space, XYZ color space and L~*a~*b~* color space. RGB color space can converse to other color space; introduced the characteristics of RGB color sensors and color aberration sensor; choose RGB color sensors TCS230 as the instrument of light receiver. As the existing of color filter, the RGB components of incidence light were separated, the intensity of which is measured by the frequency of output square wave produced by TCS230. Named this kind of frequency as intensity-frequency signals. Modeled RGB space to HSI, XYZ, L~*a~*b~* color space conversion, we proposed equation used to process light-frequency signal;3. Introduce the design of the light modules, light intensity to frequency conversion and acquisition module, lithium-ion batteries and power modules, liquid crystal display module and a cartridges used to fix light source, the sensor and measured leaves and used to defeat light. Complete procedures for PIC microcontroller used to control a button, frequency acquisition module, liquid crystal display and other functions. An experimental prototype which can display the value of light-frequency signals on LCD;4. Analysis the dependency relation between light intensity and frequency of chlorophyll content, we got several results: For leaves with width less than 14 cm, a better linear regression equation existed; RGB, XYZ color space of monadic linear regression has a better performance; linear regression of L~*a~*b~* color space has a best overall performance.