Patent ID: 7386158

Claim:
An apparatus for suppressing noise in an input image signal representing a radiographic image, comprising: a band-limited-image-signal generation unit which generates a plurality of band-limited image signals respectively representing a plurality of band-limited images belonging to a plurality of different frequency bands, based on said input image signal; an index-value obtaining unit which obtains at least one index value indicating a degree of suppression of said noise, based on information indicating an exposure dose with which said radiographic image has been produced; and a noise suppression unit which processes each of said plurality of band-limited image signals so as to suppress noise in each of said plurality of band-limited images based on said at least one index value, wherein said index-value obtaining unit obtains said at least one index value indicating the degree of suppression of the noise for each of said plurality of band-limited image signals, wherein said noise suppression unit processes each of said plurality of band-limited image signals so as to suppress the noise in each of said plurality of band-limited images based on said at least one index value obtained for said each of said plurality of band-limited image signals, and wherein said index-value obtaining unit obtains a first evaluation value from a first one of said plurality of band-limited image signals belonging to a first one of said plurality of different frequency bands and a second evaluation value from a second one of said plurality of band-limited image signals belonging to a second one of said plurality of different frequency bands which is lower than said first one of said plurality of different frequency bands, determines weights based on said information indicating the exposure dose with which the radiographic image has been produced, for use in a weighted sum of said first and second evaluation values, obtains said weighted sum, and obtains based on said weighted sum said at least one index value indicating the degree of suppression of the noise for said first one of said plurality of band- limited image signals.