Spatial and temporal nonuniformity in Infrared Focal Plane Arrays (IRFPA) severely degrades the quality of images obtained from modern infrared cameras. An efficient implementation of a nonuniformity correction algorithm is therefore necessary in real-time thermal-image visualization systems. This paper presents an FPGA-based implementation of the scene-based Constant Range algorithm for adaptive nonuniformity correction. The system processes an NTSC infrarred video signal at 30fps in real time and consumes only 157 mW of power. The performance of our system is currently limited by the input video frame rate and the external memory bandwidth, but can be readily scaled to a frame rate of more than 250fps.