Research On The Key Technologies Of Temperature Field Measurement Based On Thermal Infrared Imager

With the development of the Uncooled Infrared Focal Plane Array(UFPA)technology，Infrared Imager has been widely used in temperature measurementsystem.The technology of temperature measurement based on Infrared Imager isbecoming a new research hot issue. In this paper, we discuss the key technologies oftemperature measurement based on practical requirements. By analyzing theprinciple of infrared temperature measurement, this paper emphatically gives theprimary influential factors which affect the temperature precision. This paperproposes a series of solutions to eliminate and compensate these factors. The methodderived in this paper has been successfully applied to practice. The temperaturemeasurement system based on Infrared Imager has been developed and has achieveda good result.In view of the imaging system will be used to measure temperature, along-wave infrared uncooled imaging system which has adaptive correction functionwas designed. The system is based on FPGA, in which FPGA performs systemcontrol and image processing. The system has both analog and digital video output,in which analog video can be used to watch, while digital video with12bit precisioncan be used to measure. In order to correct non-uniform responses of the detector’sindividual elements, this paper proposed an adaptive non-uniformity correctionalgorithm based on dynamic reference temperature field, which can compensate theresponse drift according to ambient temperature. In order to eliminate the effects ofthe temperature change of the detector, a temperature control circuit based onADN8830was introduced, which can set temperature of the detector to a fixed point.Based on studies of calibration method，this paper studies the error introducedby data fitting. The data processing software adopted the curve segmented fittingmethod to build up a mathematic model of temperature and gray.IR sensor is receiving not only infrared radiation from surface of object whichtemperature is measured, but radiation from the drawtube, radiation from the shell of the camera, radiation from the environment. If nothing is done to compensate theradiation that not from the object, it is difficult to measure the real surfacetemperature. In this paper, a method that base on cooperation calibration wasintroduced. The experiment show the method has high precision.Since the emissivity of the object is an important factor influencing theaccuracy of measuring temperature, the factors that affect the emissivity werestudied. This paper presents an experimental study on the factors affect theemissivity. The factors include material，surface roughness and surface treatmenttechnology. The results of the experiment give basis to increase the temperaturemeasurement accuracy.How infrared image compression affects the temperature measurementaccuracy was studied. After analyzing the commonly used image or videocompression methods, the jpeg compression (12bit) is selected. The effects of imagecompression on the temperature measure accuracy are analyzed based on experiment.According to the analysis results, appropriate compression ratio is ascertained. Thestudy provides a good foundation for infrared image compression.