Patent ID: 6989864

Claim:
An automatic focusing device for a film scanner having a zoom lens as an imaging lens for projecting an image recorded on photo film onto an image sensor, the device comprising: a film type identifier for identifying film type of the photo film; a focus-scan range definer for defining a focus-scan range in accordance with the identified film type; a sampler for sampling pixel signals from the image sensor at different focusing positions within the focus-scan range of the imaging lens; a band pass filter for producing evaluation signals from the pixel signals, the evaluation signals being correlative with spatial frequencies of the image, and for extracting those evaluation signals within a given frequency band, the band pass filter being constituted of programmable digital filters such that the frequency band is modified in cooperation with zooming of the imaging lens; an integrator for obtaining an integration value of the extracted evaluation signals at one focusing position; and a controller for controlling the focusing position of the imaging lens based on the integration values obtained at different focusing positions.