MODULATION TRANSFER FUNCTION COMPENSATION THROUGH A MODIFIED WIENER FILTER FOR SPATIAL IMAGE QUALITY IMPROVEMENT
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Date
2010-01 , 2010-01
Authors
WONG, SOO MEE
WONG, SOO MEE
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Abstract
The usefulness of image data acquired from an imaging sensor critically depends
on the ability of the sensor to resolve spatial details to an acceptable level. This ability,
in turn, will determine the image quality in terms of sharpness. A way to describe the
performance of an imaging system and the quality of an image is to specify its
modulation transfer function (MTF). The MTF is a system quality metric that is often
used in remote sensing. It is defined as the normalized magnitUde of the Fourier
Transform of the imaging system's point spread function (PSF). The integrating effect
of the PSF of an imaging system affects the signature of a feature in the image.
Derivations..of PSF from a linear step-edge in the image can be analyzed to interpret the
MTF in frequency domain. Knowledge of MTF enables an objective assessment of
imaging system performance and preprocessing operation to compensate for the image
degradation. In. this research, a high fidelity edge projection technique which is
invariant to edge angle was developed to obtain the MTF measurements. The technique
can produce a precise and unbiased measurement. The MTF measurements were used to
model the degradation function and subsequently applied through a modified Wiener
filter for image restoration. Regularization method has been incorporated in the filter to
overcome its ill-posed problem from restoration. This atteriipt results in a significant
improvement in terms of image quality. The proposed MTF measurement and
compensation technique formed a unified system that measures MTF for imaging system
quality characterization and spatial image quality improvement. The results by the
system were analyzed and presented, they were found to be consistent. The data sets
used in the analysis were synthetically blurred remotely-sensed images simulated from
Level-2A, a product from IKONOS, a commercial remote sensing system satellite with
imaging capability of high resolution image of approximately one meter ground sample
distance in panchromatic band.
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Keywords
MODULATION TRANSFER , FUNCTION COMPENSATION