US 7,344,217 B2
Image forming apparatus and its control method, and computer program and computer readable storage medium
Hiroki Kitamura, Kawasaki (Japan); Yoshiyuki Akiba, Yokohama (Japan); Tsutomu Takada, Yokohama (Japan); Shuichi Nakamura, Kawasaki (Japan); Yusuke Yamamoto, Tokyo (Japan); Masanao Motoyama, Tokyo (Japan); Takeshi Akiyama, Tokyo (Japan); Kenzo Tojima, Tokyo (Japan); and Takaaki Nagaoka, Hadano (Japan)
Assigned to Canon Kabushiki Kaisha, Tokyo (Japan)
Filed on Apr. 11, 2006, as Appl. No. 11/279,273.
Claims priority of application No. 2005-118983 (JP), filed on Apr. 15, 2005; and application No. 2005-118984 (JP), filed on Apr. 15, 2005.
Prior Publication US 2006/0232620 A1, Oct. 19, 2006
Int. Cl. B41J 2/205 (2006.01)
U.S. Cl. 347—15  [347/116; 347/43; 358/1.9] 22 Claims
OG exemplary drawing
 
1. An image forming apparatus having an image forming unit which includes an image carrier, an exposure unit used to expose the image carrier, and a developing unit used to visualize an electrostatic latent image generated by exposure using a printing medium, comprising:
a shifting amount of color storage unit adapted to store information of shifting amount of color that represents a shifting amount of color of an exposure position in a sub-scan direction upon exposing the image carrier while scanning the image carrier in a main scan direction;
a shifting amount of color compensation amount calculator adapted to calculate a shifting amount of color compensation amount required to compensate the shifting amount of color in the sub-scan direction based on the shifting amount of color;
an image data storage unit adapted to store image data formed by a plurality of pixels;
an address converter adapted to convert a coordinate of a read address of said image data storage unit based on a shifting amount of color in a pixel unit of the shifting amount of color compensation amount, and to read out pixel data of a pixel of interest from said image data storage unit in accordance with the converted address information;
a pixel color density converter adapted to convert a pixel color density of the pixel data read out from said image data storage unit by said address converter based on a shifting amount of color less than a pixel unit of the shifting amount of color compensation amount;
a half-tone processing unit adapted to perform half-tone processing of the pixel data which has undergone the color density conversion by said pixel color density converter;
an exceptional processing unit adapted to perform exceptional processing of the pixel data which has undergone the color density conversion by said pixel color density converter;
a process determination unit adapted to detect a feature of image data formed by pixels in a predetermined region having the pixel of interest as a center of the image data stored in said image data storage unit, and to determine one of the exceptional processing and the half-tone processing to be selected; and
an output unit adapted to select a processing result of one of said exceptional processing unit and said half-tone processing unit based on a determination result of said process determination unit, and to output the selected processing result as an exposure control signal of the exposure unit.