Infrared signature: Theory and example of practical measurement methods

A practical method for the calibration of infrared cameras, for application from 0°C to over 600°C, is presented. The calibration of image in Digital Level to Radiance is achieved by measuring the camera output while imaging an extended area blackbody at different temperatures. The linear relationship between the camera output (Digital Level) and the blackbody emitted radiance is derived. When acquiring new scenes, the a priori calculated linear relation is applied to the scene image to calculate, pixel by pixel, the related Apparent Radiance. Non Uniformity Correction algorithm and Atmospheric Transmission simulating tools (e.g. LOWTRAN) are presented to improve the detector responsiveness and to estimate the absolute radiance emitted by the source respectively. A method to virtually increase the dynamic range of temperature for the acquired scene is described. An example of infrared signature measurement is also presented.