Study of Scene - Based Nonuniformity Compensation in Infrared Focal Plane Arrays

Infrared Focal Plane Arrays (FPAs) are used in a wide variety of military and industrial applications which require the collection of low noise, high resolution images. In many of these applications, the dominant noise results from array response nonuniformities. For low noise applications (e.g., detection of low contrast, unresolved targets), correction for the nonuniform array response is critical for achieving the maximum sensitivity of these arrays. Two classes of techniques for reducing the effects of nonuniformity are source-based compensation, which employs the use of one or more uniform calibrated sources, and scene-based compensation, which uses scene data to estimate nonuniformity. This thesis evaluates the performance of both source-based and scene-based compensation techniques using experimental sensor data. Array nonuniformities were first characterized and then used to predict the performance of the different compensation techniques. Two-point source-based nonuniformity compensation techniques, which use uniform calibration sources at two temperatures, were applied to blackbody images over a wide range of temperatures and shown to reduce spatial variations to an average of 0.82 sensor counts (0.03'C). One-point compensation techniques performed as well only near the calibration temperature; over the wide temperature range, variations averaged 14.7 sensor counts (0.5"C). Scene-based algorithms were evaluated using measured IR images and were found to decrease spatial variation below that of the two-point compensation technique, from 43 counts to as low as 17 counts, as a result of the algorithms' clutter rejection capabilities. The effects of scene-based techniques on target suppression were not evaluated as a part of this thesis. VI-A Company: MIT Lincoln Laboratory Thesis Supervisor: David H. Staelin Title: Assistant Director, Lincoln Laboratory