2 May 2007 Impact of path radiance on MWIR and LWIR imaging
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Abstract
Atmospheric radiance occurs in both the MWIR and LWIR primarily as a consequence of thermal emission by the gases and aerosols in the atmosphere. If this radiation originates between a scene and a thermal imaging sensor, it's called path radiance. In thermal IR imagery, path radiance reduces scene radiation contrast at the entrance pupil. For ground based sensors, this effect would be most significant in search systems with wide fields of view (WFOV) that image a large range depth of field. In WFOV search systems, the sensor display gain and level are typically adjusted to optimize the contrast of targets and backgrounds at the closer ranges. Without compensation in WFOV imagery, high path radiance can mask distant targets in the detection process. However, in narrow fields of view (NFOV), path radiance can have less of an impact since targets and backgrounds will be at about the same range and thus have the same path radiance. As long as the NFOV radiation contrast exceeds the system noise, sensor display gain and level adjustments, or image processing, if available, can be used to boost the contrast at the display. However, there are some imaging conditions that are beyond compensation by display contrast adjustments or image processing. Using MODTRAN, this paper examines the potential impacts of path radiance from the phenomenological point of view on target-tobackground contrast and signatures (&Dgr;T) for dual band thermal imaging systems
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Van A. Hodgkin, Tana Maurer, Carl Halford, Richard Vollmerhausen, "Impact of path radiance on MWIR and LWIR imaging", Proc. SPIE 6543, Infrared Imaging Systems: Design, Analysis, Modeling, and Testing XVIII, 65430O (2 May 2007); doi: 10.1117/12.721364; https://doi.org/10.1117/12.721364
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