Abstract
Images rendered by uncooled microbolometer-based infrared (IR) cameras are severely degraded by the spatial non-uniformity (NU) noise. The NU noise imposes a fixed-pattern over the true images, and the intensity of the pattern changes with time due to the temperature instability of such cameras. In this paper, we present a novel model and a compensation algorithm for the spatial NU noise and its temperature-dependent variations. The model separates the NU noise into two components: a constant term, which corresponds to a set of NU parameters determining the spatial structure of the noise, and a dynamic term, which scales linearly with the fluctuations of the temperature surrounding the array of microbolometers. We use a black-body radiator and samples of the temperature surrounding the IR array to offline characterize both the constant and the temperature-dependent NU noise parameters. Next, the temperature-dependent variations are estimated online using both a spatially uniform Hammerstein-Wiener estimator and a pixelwise least mean squares (LMS) estimator. We compensate for the NU noise in IR images from two long-wave IR cameras. Results show an excellent NU correction performance and a root mean square error of less than 0.25 C, when the array’s temperature varies by approximately 15 C.
Highlights
Microbolometers are a type of infrared (IR) radiation detector developed by Honeywell in the 80s, to be used as focal plane arrays (FPAs) in imaging systems [1]
We present a novel model for the spatial NU noise and the raw output of uncooled microbolometer-based IR cameras
We plot the roughness metric of the raw video as a reference. It can be observed from the figure that all the non-uniformity correction (NUC) methods effectively compensate for the NU noise because their roughness metrics are lower than the roughness metric of the raw video
Summary
Microbolometers are a type of infrared (IR) radiation detector developed by Honeywell in the 80s, to be used as focal plane arrays (FPAs) in imaging systems [1]. The bolometer feature of these sensors means that temperature variations in the sensor produce changes in its electrical resistance. Such a change can be, in turn, measured by means of simple electrical circuits. The changes in the electrical resistance are processed in a digital fashion to obtain read-out values quantifying the amount of IR radiation absorbed by the detector. Unlike other technologies such as HdCdTe, microbolometers do not require cryogenic cooling systems to operate in the long-wave infrared (LWIR) band [2]
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