Patent ID: 6559981
Filing Date: 2003-05-06
Classification: H04N

Abstract:
An image reading apparatus for reading an image on a document by irradiating light from a light source onto the document, receiving light reflected from the document or transmitted through the document, and converting the thus reflected or transmitted light into electric signals, said image reading apparatus comprising:a color image pick-up system having image pick-up element groups, each of said groups having a plurality of image pick-up element rows arranged in parallel, each of said rows having a plurality of linearly arrayed image pick-up elements, the rows in the same group being shifted one from another by an amount smaller than a width of one of said image pick-up elements in a direction in which said image pick-up elements are linearly arrayed, said color image pick-up system outputting data on pixels; an A/D converter which converts said data outputted from said color image pick-up system into digital data; an averaging circuit which calculates and outputs average data between digital data on a this-time pixel and a last time pixel on a line; a selection circuit to which said digital data on said this-time pixel and said average data outputted from said averaging circuit are inputted; a first comparison circuit which generates a first signal for selecting said data on said this-time pixel if a differential value between said data on said this-time and last time pixels data is larger than a predetermined setting value, generates a second signal for selecting said average data outputted from said averaging circuit if said differential value is not larger than the predetermined setting value, and supplies either of said first and second signals to said selection circuit; and a second comparison circuit which generates a third signal for selecting said data on said this-time pixel if said data on said this-time pixel have a value indicative of a level brighter than a predetermined level, generates a fourth signal for selecting said first or second signal outputted from said first comparison circuit if said data on said this-time pixel have a value indicative of a level darker than said predetermined level, and supplies either of said third and fourth signals to said selection circuit.