Correctability and long-term stability of infrared focal plane arrays

The temperature resolution of infrared focal plane arrays is limited by tem poral and spatial noise. The spatial noise usually is partially removed by correction procedures. These correction procedures reduce the spatial noise to a magnitude below the temporal noise. The correctability c defined as t he ratio of the spatial to the temporal noise is a figure of merit for the state of the correction. We consider the transient degradation of the corre ctability after correction. A new figure of merit, the long-term stability time constant tau(lts) is introduced. This time indicates the duration afte r a nonuniformity correction during which the spatial noise increases to va lues higher than that of the temporal noise. Several staring infrared focal plane arrays differing in size and in detector material are investigated. The correctability c is determined after various correction procedures and the long-term stability time tau(lts) is measured. The degradation of the c orrectability is caused by a few individual pixels in the detector array. W e can classify three different types of "bad pixels, which degrade the corr ectability. These are weak pixels that show a low responsivity and flickeri ng and drifting pixels that show excessive 1/f-noise. (C) 1999 Society of P hoto-Optical Instrumentation Engineers. [S0091-3286(99)01805-X].