With the in-depth development of the infrared physics and infrared technology

the measurement of target radiation characteristics is widely appreciated. And the infrared detector radiometric calibration is a fundamental work. This paper establish a radiometric calibration system

the absolute radiometric calibration of the 3~5 m infrared focal plane arrays. Firstly

give the radiometric calibration mathematical model

developed a calibration process and the radiometric calibration experiment. As infrared standard source and the impact of environmental volatility

a weighted least squares radiation calibration optimization is proposed. The radiation characteristic measurement experiment was carried out outside the field. Results show that the inversion error of optimization method is better than 4%. The accuracy of radiometric calibration was improved. And the results meet the actual needs of the project.