Patent ID: 6567189
Filing Date: 2003-05-20
Classification: H04N

Abstract:
An image reading apparatus comprising:an optical unit adapted to focus an optical image of an original; an image sensor for linearly arranging pluralities of photoelectric-conversion pixels, accumulating a linear optical image focused by said optical unit in said photoelectric-conversion pixels as signal electric charges, and successively outputting said signal electric charges as image signals every predetermined period; a scanning unit adapted to scan said original in a sub-scanning direction vertical to a main scanning direction serving as the direction of said linear optical image; and a pixel-shifting unit adapted to shift the relative positions between the position of an optical image focused on said image sensor through said optical unit and said photoelectric-conversion pixels on the unit basis of substantially 1/N (N is an integer) of the pixel pitch of said image sensor in said main scanning direction; wherein said image sensor is a linear image sensor, sub-scanning is performed by said scanning unit N times, and pixel shifting is performed on the unit basis of substantially 1/N of the pitch between pixels of said linear image sensor; wherein the sub-scanning-directional moving distance of said scanning unit at every repetition cycle of a line sequential signal output from said linear image sensor is made almost equal to the pitch between pixels of said linear image sensor, and the position of the optical image of each of said line sequential signals focused on said linear image sensor through said N repetitions of scanning is shifted by a value equivalent to substantial 1/N the pitch between pixels of said linear image sensor; and, wherein when expressing an optional pixel at any scanning as the xth pixel from the end in a predetermined main scanning direction in an image reading range on the yth line from the end in a predetermined sub-scanning direction in the image reading range, the pixel data at a position between the xth pixel and the (x+1)th pixel on the yth line and shifted from the xth pixel by k/N (k is an integer and kthe data at a position between the xth pixels on the yth line and the (y+1)th line and shifted from the pixel on the yth line by m/N (m is an integer and m