Image processing module for high-speed thermal camera with cooled detector

Abstract

Infrared cameras are used in various military applications for early detection and observation. In applications where very fast image acquisition is needed the so called cooled detectors are used. Cooled detectors are a kind of detectors that demands cryogenic cooling, but in return provide exceptional performance and temperature sensitivity with low integration times. These features predestinate cooled detectors for special purposes like airborne systems, where fast and precise infrared radiation measurement is needed. Modern infrared cooled detector arrays like HgCdTe Epsilon detector from Sofradir with spectral range of 3.5μm-5μm can provide high frame rate reaching 140Hz with full frame readout. Increasing frame rates of cooled infrared detectors demands fast and efficient image processing modules for necessary operations like nonuniformity correction, bad pixel replacement and visualization. For that kind of detector array a fast image processing module was developed. The module is made of two separate FPGA modules and configuration processor. One FPGA was responsible for infrared data processing, and was performing nonuniformity correction, bad pixel replacement, linear and nonlinear filtering in spatial domain and dynamic range compression. Second FPGA was responsible for interfacing infrared data stream to standard video interfaces. It was responsible for frame rate conversion, image scaling and interpolation, and controlling ASICs for video interface realization. Both FPGAs use several external resources like SRAM and DRAM memories. The input interface was developed to connect with Epsilink board which is a standard proximity board provided by Sofradir for this kind of detector. The image processing chain is capable of performing real-time processing on data stream of volume up to about 40 Megapixels per second.