Comparison of turbulence MTF and aerosol MTF

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1 Scopus citations


Image quality is degraded when propagating through the atmosphere. Atmospheric turbulence and forward light scattering by aerosols between the object and the imaging systems are the main degrading factors in image quality. It is practical to characterize the image degradation in terms of atmospheric Modulation Transfer Function (MTF). Each of the degrading factors has its own MTF. Several models which are based on the solution to the radiative transfer equation under the assumption of small angle approximation exist. In this research the overall atmospheric MTF of an horizontal path was measured using an imaging system with a narrow field of view. Measurements of the turbulence MTF alone at the same time and over the same optical path were also made. These measurements were also taken at several wavelengths over the visible and near IR. Comparison of the overall measured MTF and the turbulence MTF suggest that the atmospheric MTF is not composed of turbulence MTF alone. These measurements show clearly that image quality is degraded by aerosols, although the spatial frequencies at which the degradation occurred were up to 5 to 15 cycles per mrad rather than radian. This contradicts existing concepts. Atmospheric MTF measurements were taken by several methods such as the point spread function of an HeNe laser beam propagating through a horizontal atmospheric path and the line spread function of an edge defined by a bar chart composed of several varying width line pairs of black and white stripes. In each of these measurements it was found that image quality is degraded by aerosol MTF in addition to turbulence MTF, and the spatial frequency cutoffs were similar. The differences between the measured aerosol MTF and the aerosol MTF models can be explained by solving the radiative transfer equation and taking into account the narrow field of view of the imaging system.

Original languageEnglish
Title of host publicationProceedings of SPIE - The International Society for Optical Engineering
PublisherPubl by Int Soc for Optical Engineering
Number of pages12
ISBN (Print)0819408530
StatePublished - 1 Dec 1992
EventAtmospheric Propagation and Remote Sensing - Orlando, FL, USA
Duration: 21 Apr 199223 Apr 1992

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X


ConferenceAtmospheric Propagation and Remote Sensing
CityOrlando, FL, USA

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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