Image forming apparatus and its control method

A method of controlling an image forming apparatus in which image forming units each having an image carrier, an exposure unit for scanning exposure on the image carrier, and a developing unit for visualizing an electrostatic latent image generated by exposure using a color former are juxtaposed in a conveying direction of a print medium, comprising:

• a step of storing image data to be formed by each image forming unit in predetermined image data storage means;
• a read step of reading out, from predetermined exposure shifting amount storage means which stores shifting amount information indicating a shifting amount with respect to a scanning direction on the image carrier of each image forming unit, the exposure shifting amount information;
• a coordinate conversion step of converting coordinates of a read address of the image data storage means on the basis of the readout exposure shifting amount information, and reading out image data according to the converted address information;
• a correction step of correcting a tone of pixel data read out in the coordinate conversion step on the basis of the converted address information;
• a halftone step of applying predetermined halftone processing to the pixel data obtained in the correction step;
• and
• an output step of outputting the pixel data obtained in the halftone step as an exposure control signal of the exposure unit of the corresponding image forming unit.

An image forming apparatus in which image forming units each having an image carrier, an exposure unit for scanning exposure on the image carrier, and a developing unit for visualizing an electrostatic latent image generated by exposure using a color former are juxtaposed in a conveying direction of a print medium, comprising:

• image data storage means for storing image data to be formed by each image forming unit;
• exposure shifting amount storage means for storing shifting amount information indicating a shifting amount with respect to a scanning direction on the image carrier of each image forming unit;
• coordinate conversion means for converting coordinates of a read address of said image data storage means on the basis of the exposure shifting amount information stored in said exposure shifting amount storage means, and reading out image data according to the converted address information;
• buffer means for storing pixel data read out by said coordinate conversion means for a plurality of lines;
• determination means for determining, based on pixel data of interest and a surrounding pixel data group stored in said buffer means, if the pixel data of interest belongs to an image edge;
• first processing means for, when said determination means determines that the pixel of interest belongs to a non-image edge, applying halftone processing for the non-image edge to the pixel data of interest;
• correction means for, when said determination means determines that the pixel of interest belongs to the image edge, correcting a tone of the pixel data of interest stored in said buffer means on the basis of address information used upon conversion by said coordinate conversion means;
• second processing means for applying processing for an edge different from said first processing means to the pixel data obtained by said correction means;
• and
• output means for outputting the pixel data obtained by said first and second processing means as an exposure control signal of the exposure unit of the corresponding image forming unit on the basis of the determination result of said determination means.

A method of controlling an image forming apparatus in which image forming units each having an image carrier, an exposure unit for scanning exposure on the image carrier, and a developing unit for visualizing an electrostatic latent image generated by exposure using a color former are juxtaposed in a conveying direction of a print medium, comprising:

• a step of storing image data to be formed by each image forming unit in predetermined image data storage means;
• a read step of reading out, from predetermined exposure shifting amount storage means which stores shifting amount information indicating a shifting amount with respect to a scanning direction on the image carrier of each image forming unit, the exposure shifting amount information;
• a coordinate conversion step of converting coordinates of a read address of the image data storage means on the basis of the readout exposure shifting amount information, and reading out image data according to the converted address information;
• a step of storing, in buffer means, pixel data read out in the coordinate conversion step for a plurality of lines;
• a determination step of determining, based on pixel data of interest and a surrounding pixel data group stored in the buffer means, if the pixel data of interest belongs to an image edge;
• a first processing step of applying, when it is determined in the determination step that the pixel of interest belongs to a non-image edge, applying halftone processing for the non-image edge to the pixel data of interest;
• a correction step of correcting, when it is determined in the determination step that the pixel of interest belongs to the image edge, a tone of the pixel data of interest stored in the buffer means on the basis of address information used upon conversion in the coordinate conversion step;
• a. second processing step of applying processing for an edge different from the first processing step to the pixel data obtained in the correction step;
• and
• an output step of outputting the pixel data obtained in the first and second processing steps as an exposure control signal of the exposure unit of the corresponding image forming unit on the basis of the determination result of the determination step.

An image forming apparatus in which image forming units each having an image carrier, an exposure unit for scanning exposure on the image carrier, and a developing unit for visualizing an electrostatic latent image generated by exposure using a color former are juxtaposed in a conveying direction of a print medium, comprising:

• image data storage means for storing image data to be formed by each image forming unit;
• exposure shifting amount storage means for storing shifting amount information indicating a shifting amount with respect to a scanning direction on the image carrier of each image forming unit;
• configuration information storage means for storing information associated with a configuration of each image forming unit;
• coordinate conversion means for converting coordinates of a read address of said image data storage means on the basis of the exposure shifting amount information stored in said exposure shifting amount storage means and the configuration information stored in said configuration information storage means, and reading out image data according to the converted address information;
• determination means for determining, based on pixel data of interest and a surrounding pixel data group obtained by said coordinate conversion means, if the pixel data of interest belongs to an image edge;
• first processing means for, when said determination means determines that the pixel of interest belongs to a non-image edge, applying predetermined halftone processing;
• correction means for, when said determination means determines that the pixel of interest belongs to the image edge, correcting a tone of the pixel data of interest on the basis of the converted address information;
• second processing means for applying processing for an edge different from said first processing means to the pixel data of interest after correction by said correction means;
• and
• output means for outputting one of the pixel data obtained by said first and second processing means as an exposure control signal of the exposure unit of the corresponding image forming unit on the basis of the determination result of said determination means.

A method of controlling an image forming apparatus in which image forming units each having an image carrier, an exposure unit for scanning exposure on the image carrier, and a developing unit for visualizing an electrostatic latent image generated by exposure using a color former are juxtaposed in a conveying direction of a print medium, comprising:

• a step of storing image data to be formed by each image forming unit in predetermined image data storage means;
• a step of reading, from exposure shifting amount storage means which stores shifting amount information indicating a shifting amount with respect to a scanning direction on the image carrier of each image forming unit, the shifting amount information;
• a step of reading, from configuration information storage means which stores information associated with a configuration of each image forming unit, the configuration information;
• a coordinate conversion step of converting coordinates of a read address of the image data storage means on the basis of the read exposure shifting amount information and the configuration information, and reading out image data according to the converted address information;
• a determination step of determining, based on pixel data of interest and a surrounding pixel data group obtained in the coordinate conversion step, if the pixel data of interest belongs to an image edge;
• a first processing step of applying, when it is determined in the determination step that the pixel of interest belongs to a non-image edge, predetermined halftone processing;
• a correction step of correcting, when it is determined in the determination step that the pixel of interest belongs to the image edge, a tone of the pixel data of interest on the basis of the converted address information;
• a second processing step of applying processing for an edge different from the first processing step to the pixel data of interest after correction in the correction step;
• and
• an output step of outputting one of the pixel data obtained in the first and second processing steps as an exposure control signal of the exposure unit of the corresponding image forming unit on the basis of the determination result of the determination step.