To remove grain by spatially filtering images.
A method for removing the grain by spatially filtering the images in an optical navigation system is provided. While performing navigation using a first filter, an ordered collection of correlation values is generated. Whether or not a ridge is present in a correlation surface described by the values of the ordered collection is tested. When the ridge is present, the navigation is started using a second filter. During the navigation, the ordered collection of the correlation values produced while the second filter is in use is tested. The navigation is continued while the examination reveals the absence of the ridge and the navigation with the first filter is restarted when it reveals the presence of the ridge. For the second filter, the filter most effectively dealing with the revealed ridge is selected from third and fourth filters spatially oriented at 90° to one another.
MOORE CHARLES E
WALLACE HUGH
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