Operational Measurements for Infrared Camera Characterization

ABSTRACT: The detection, location, identification and recognition are very important activities for the air forces. Imaging systems are tools used for those functions, so it is mandatory to characterize those systems to really know their actual operational limits. This paper presents a set of measurements for spectral, radiometric and spatial camera characterization to be applied to imaging systems operating in the thermal infrared. A SC5600 camera manufactured by FLIR® Systems was used and assembled with lenses of 27 or 54 mm equivalent focal length. The camera spectral characterization was done by comparison to a calibrated system composed by thermal source, monochromator and a broadband reference detector. The radiometric characterization was performed using an extensive blackbody (CI Systems) for temperatures between 10 and 55 ºC to evaluate the camera accuracy and obtain the calibration curves. The spatial characterization was carried out using the same extensive blackbody and 2 standard USAF 1951 machined targets, one made of steel and other of aluminum, serving as masks for the blackbody. Using recycled material, a homemade extended blackbody for outdoor use was built. The results obtained using the 2 blackbodies in laboratory were similar.

摘要：探测、定位、识别与辨识是空军极为关键的作战任务。成像系统是实现上述任务的核心工具，因此对这类成像系统进行特性表征以明确其实际作战极限，是一项必要工作。本文提出一套适用于热红外（thermal infrared）波段成像系统的相机光谱、辐射度与空间特性表征测量方案。实验采用FLIR系统（FLIR® Systems）制造的SC5600型相机，并搭配27 mm或54 mm等效焦距（equivalent focal length）的镜头。相机的光谱特性表征通过与由热辐射源（thermal source）、单色仪（monochromator）及宽带参考探测器（broadband reference detector）组成的校准系统进行比对完成。辐射度特性表征则采用CI系统（CI Systems）的大型黑体辐射源（blackbody），在10至55 ℃的温度区间内开展实验，以评估相机的测量精度并获取校准曲线（calibration curves）。空间特性表征实验同样使用该大型黑体辐射源，搭配2件标准USAF 1951型加工靶标：一件为钢制，另一件为铝制，作为黑体辐射源的掩模（mask）。研究人员利用再生材料搭建了一款可户外使用的自制扩展黑体辐射源（extended blackbody）。实验室环境下使用两款黑体辐射源所得的实验结果高度一致。