Physical Model Building And Demonstration Of Infrared Thermometry

IR(infrared) thermometer has been widely used in industry, national defense fields because of its many merits. With the development of science and the progress of our society as well as the improving of people's living level, the demanding of non-contacting IR thermometer is more and more big. For example, during SARS in 2003, the demanding reaches a high level. Non-contacting IR thermometer can measure the object's temperature without contacting the object, which makes it the best choice in some more dangerous vocation. So, this demands a higher standard for the measuring accuracy of IR thermometer system. In the research of IR thermometer system, the foundation of the model for IR thermometer system and the research on precision of the model are main difficulties and the key technologies. Also they are the very interest subject of IR researchers all over the world. This article by the numbers expatiates on the effect of each factor in the model of IR thermometer system in theory and does some systemic research on the model based on a series of experiment.In the chapter 1: the development of radiation thermometry and IR thermometer has been reviewed and the problems were analyzed from technique degree. And it introduced the main objects and study situation. It analyzes the development status in this area inside and outside the country. And it introduces the main objects and directions.In the chapter 2: Introduces some basic conception based on infrared theory including the conception of blackbody, emissivity, reflectivity, transmissivity, spectral irradiance, integralirradiance. Also includes some basic law of infrared physics including Planck's Law, Wien's Displacement Law, Stefan-Boltzmann'Law, Lambert's Cosine Law and Kirchhoff's Law. And then we get the conception of effective radiation. We talk about the means of infrared temperature measurement and the analyze of their model of thermometry. All Radiation Temperature Measurement Method: It uses blackbody calibrated instrument to determine the object's temperature based on measuring the object's total radiant power whose wavelength is from 0 to∞and covers the all range of spectrum. Luminance Temperature Measurement Method: The luminance temperature of the object is in a narrowband range of spectrum. And we can use the temperature of the blackbody which has the same radiant power with the object to denote the object's temperature. Double Wavelength Temperature Measurement Method: It is based on the measurement of the power ratio of tow certain wavelengthλ1 andλ2 .We use the blackbody calibrating instrument to fix on the object's temperature.In the chapter 3: It is the synthetical analysis of the factors which affect the accuracy of infrared temperature measurement. First, there is the model of IR imaging and the transmitting effect of atmosphere, including the composing and the optical characteristic of atmosphere, the atmosphere effect model of infrared image, experience calculation of the attenuation of atmosphere. And then there is the emissivity of the object and its effect on the accuracy of IR thermometer system including the factors which affect the value of the emissivity of the object ,the enactment of the emissivity and proceeding to which has to be paid attention when we measure the emissivity. Finally there is the background's effect on the accuracy of IR temperature measurement. They are the effect from the contrast between the object and the background, the effect from the temperature of the circumstance and the step which can reduce theerror from the effect of the background.In the chapter 4: The establishment of the model of IR temperature measurement. First we introduce the physical principle of IR thermometer and the working process table of IR thermometer system. In former chapters we have known that because the IR temperature measurement system belongs to the instrument of narrowband-spectrum radiation imaging measurement, the accuracy of the measurement is affected by the surface characteristic (such as the emissivity and the reflectivity), the transmissivity of atmosphere, the emissivity of atmosphere, the temperature of the background, the temperature of atmosphere and so on when IR thermometer works. When there are errors in these factors measurement, the accuracy of the temperature measurement of the object will be affected. But as we known, the model is greatly determined by the experiential coefficient not by the theory or math calculation. On account of this behalf, a certain model is not always fit for different types of object or different circumstance condition. So we must measure many data in the area to get an exact result for the model. In another hand, some factors in the model need to be approximated to get the model which is better for the project calculating and more useful. In this chapter first we make a experiment of the demarcating for gray images based on the radiation theory and the working principle of IR temperature measurement system. And then analyze the effect on IR thermometer from the every factor. Gain the IR temperature measurement model including the object surface temperature, emissivity and reflectivity,transmissivity of atmosphere, the temperature of circumstance and the temperature of atmosphere. This has a very important practical sense for improving the accuracy of the IR thermometer and decrease unnecessary measurement error. Finally we apply the model. We can see from the pictures that after apply the model it can display the temperature of different gray areas.Although this will not be fit for the too much of the accuracy, it can achieve the temperature measurement function in common accuracy request if we emendate and improve it.Finally there is a sum-up. Because of the limiting in condition and time, there are still some unfixed physical parameters in our model, but we believe these questions can be resolved in the future research.Infrared detection technology is to be surely enhanced largely with the development of our society and the progress of the science. In the market, there already has been non-contacting infrared thermometer which detection accuracy is perfect. People are more and more interesting in the research on the model accuracy of IR temperature measurement, so we believe in the future the shortages are surely to be resolved and more and more products with good quality but low price will be produced to meet the society's need.