Signal Processing For Staring Infrared Images

AbstractThe signal from a staring infrared imager, initially in the charge domain, is charac-terized by low contrast and nonuniformities. To achieve high performance, the signal pro-cessor should have low noise and operate with background suppression. Fixed pattern noisecompensation must also be available. Low noise multiplexing can be achieved with chargecoupled devices (CCD). With a hybrid focal plane, background suppression at the Si CCDinput can be achieved with charge partitioning, charge skimming, ac- coupling or fill /spillgain reduction. Fixed pattern noises arising from detector variations, CCD input thresholdvariations, charge transfer process and other sources, must be compensated electronicallyusing optical calibration. A performance model of the input circuit taking into accountthe various noise sources will be discussed and compared with experimental data. Data onfocal plane fixed pattern noises will be presented. Various techniques to implement thenonuniformity correction, especially in a tactical system, will also be discussed.IntroductionStaring infrared images, compared to first generation scanned imagers, are made withlarge, two -dimensional arrays of high density, small size detectors. Capable of inte-grating the signal charge generated from incoming photon flux for a longer time, the star-ing imager can achieve a significantly higher sensitivity. Additional advantages of notneeding a mechanical scanner and having fewer bonding leads increase the system reliabil-