Proposed standard for infrared focal plane array nonuniformity measurements

Abstract

The staring IR focal plane array (IRFPA), once a novelty, has now evolved into an important technology being used in a variety of imaging systems. These systems frequently include schemes for nonuniformity correction (NUC) that reduce artifacts caused by lack of detector uniformity within the IRFPA. The effect of these artifacts is a fixed pattern that interferes with the desired image of the scene. Although the resulting imagery can be substantially improved using NUC, significant residual fixed pattern noise (RFPN) typically remains. As IRFPAs become more standard in designs for missile seekers, measurement methods related to RFPN should be standardized. This paper introduces an improved method with which the IRFPA fixed pattern noise can be measured both before and after NUC algorithms have been applied. The proposed standard provides two key benefits: (1) consistent quantification of the specific characteristics of the inherent spatial noise or residual post-NUC RFPN that significantly impact system performance; and (2) a standardized process that facilitates IRFPA and NUC comparisons and measures progress toward design improvement. The approach considers the 3D noise modeling technique proposed for FLIR systems and modifies the technique to account for the spatial scale and power spectrum of the RFPN. The resulting characterization is called the simplified power spectrum (SPS). Residual low-frequency nonuniformities such as gradients across the entire array may not be as important as high-frequency, uncorrelated variations; the SPS allows differentiation of these RFPN effects. The algorithms and test procedures required for the standard are presented in the paper.