title: Atmospheric modulation transfer function in the infrared.
abstract: In high-resolution ultranarrow field-of-view thermal imagers, image quality over relatively long path lengths is typically limited by atmospheric degradation, especially atmospheric blur. We report our results and analyses of infrared images from two sites, Fort A. P. Hill and Aberdeen Proving Ground. The images are influenced by the various atmospheric phenomena: scattering, absorption, and turbulence. A series of experiments with high-resolution equipment in both the 3-5- and 8-13-microm regions at the two locations indicate that, as in the visible, image quality is limited much more by atmosphere than by the instrumentation for ranges even of the order of only a few kilometers. For paths close to the ground, turbulence is more dominant, whereas for paths involving higher average elevation, aerosol modulation transfer function (MTF) is dominant. As wavelength increases, turbulence MTF also increases, thus permitting aerosol MTF to become more dominant. A critical role in aerosol MTF in the thermal infrared is attributed to absorption, which noticeably decreases atmospheric transmission much more than in the visible, thereby reducing high-spatial-frequency aerosol MTF. These measurements indicate that atmospheric MTF should be a basic component in imaging system design and analysis even in the infrared, especially as higher-resolution hardware becomes available.
authors.affiliation: Department of Electrical and Computer Engineering, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel.
authors.forename: Kobi
authors.initials: K
authors.lastname: Buskila
authors.forename: Shay
authors.initials: S
authors.lastname: Towito
authors.forename: Elad
authors.initials: E
authors.lastname: Shmuel
authors.forename: Ran
authors.initials: R
authors.lastname: Levi
authors.forename: Natan
authors.initials: N
authors.lastname: Kopeika
authors.forename: Keith
authors.initials: K
authors.lastname: Krapels
authors.forename: Ronald G
authors.initials: RG
authors.lastname: Driggers
authors.forename: Richard H
authors.initials: RH
authors.lastname: Vollmerhausen
authors.forename: Carl E
authors.initials: CE
authors.lastname: Halford