Research On Absolute Calibration Technology Of Infrared Radiometer

With the wide application of infrared radiation measuring instruments in deep space exploration,earth observation,low-light night vision,infrared guidance,radiation measurement and other fields.Related fields put forward high-precision measurement requirements for infrared radiation measuring instruments such as bandpass,dispersion,and interferometric infrared radiometers.The premise of high-precision measurement is the high-precision absolute calibration of various infrared radiometers.However,the traditional method has the phenomenon of low calibration accuracy.In view of this situation,this paper starts from analyzing the working principle of three typical infrared radiometers,and studies the absolute calibration method of infrared radiometers.Taking the bandpass infrared radiometer as the calibration object,the absolute calibration of the bandpass infrared radiometer is divided into two parts,the relative radiometric calibration and the absolute radiometric calibration,which are carried out successively by combining the standard detector and the standard radiation source.Aiming at the shortcomings of the traditional two-point calibration method,a multi-temperature and multi-level method is used to establish an absolute calibration database to realize the absolute calibration of the infrared radiometer and improve the measurement accuracy of the infrared radiometer.Firstly,according to the working principle of three types of infrared radiometers,the absolute calibration principle of various types of infrared radiometers is theoretically analyzed.For the most complex bandpass infrared radiometer with absolute calibration,this paper designs and builds a relative radiation calibration device based on cavity blackbody,reflection optical system,infrared monochromator,lock-in amplifier and cavity pyroelectric detector.The absolute radiation calibration device is designed and built with cavity blackbody,water-cooled diaphragm,and off-axis reflection collimator.Realize the absolute calibration of infrared radiometer in the temperature range of 100??1000? in the near infrared to far infrared band.Secondly,based on the built calibration device,the infrared radiometer was calibrated relative to radiation,and the relative spectral power responsivity of the infrared radiometer in the 1?m-3?m,3?m-5?m and 8?m-14?m bands was obtained.According to the relative spectral power responsivity of each band,the standard radiance of the corresponding band is calculated,and then the infrared radiometer is calibrated with absolute radiation to obtain the response signal and absolute radiance responsivity of the infrared radiometer at each standard blackbody temperature point.To establish the absolute calibration standard database of infrared radiometer.Based on the standard database,the blackbody surface brightness temperature measurement experiment was carried out.Compared with the measurement results of the traditional two-point method,the establishment of the absolute calibration standard database reduces the maximum relative error of radiation temperature measurement to 2.5%.Finally,the influencing factors of absolute calibration of infrared radiometer are analyzed and the uncertainty evaluation of absolute calibration is completed.Among them,the maximum relative error of absolute radiance responsivity is only 0.23% when the standard black body temperature is stable to the working state,and the maximum relative error is 1.2% when the standard black body temperature is not stable to the working state.When the modulation frequency of the chopper of the infrared radiometer works at the center frequency of the acquisition amplifying circuit,the absolute radiance responsivity obtains the optimum value with good repeatability and large amplitude.The maximum combined standard uncertainty of relative radiometric calibration and absolute radiometric calibration are 2.86% and 3.22%,respectively.To sum up,the method used in this paper can better realize the unified system-level absolute calibration of the infrared radiation measurement value in the wide spectral band,and combined with the established absolute calibration database,it can effectively improve the measurement accuracy of the infrared radiometer.It has important practical significance for the accurate and objective high-precision absolute calibration of infrared radiometers.