Image forming apparatus that accurately detects sheet in the feeding direction, and method thereof

An image forming apparatus comprising:

• an image forming section that forms an image of an original on a sheet;
• a resist roller that conveys the sheet to said image forming section in predetermined timing;
• a sheet reading section having a plurality of read pixels for reading the image of the sheet and disposed in an area which the sheet passes, in a such a fashion that the plurality of read pixels are arranged in a direction perpendicular to a direction in which the sheet is fed;
• a leading edge detecting section that detects a leading edge of the sheet by repeatedly reading the plurality of read pixels with a predetermined period;
• a start time determining section that is responsive to the leading edge of the sheet being detected by said leading edge detecting section, for determining timing for starting image formation in the direction in which the sheet is fed by said image forming section;
• a side edge detecting section that detects a side edge of the sheet by repeatedly reading the plurality of read pixels read by said leading edge detecting section;
• and
• a writing start position adjusting section that adjusts a writing start position in which the image of the original is written by said image forming section in the direction perpendicular to the direction in which the sheet is fed, based on the side edge of the sheet detected by said side edge detecting section.

An image formation control method for an image forming apparatus comprising an image forming section that forms an image of an original on a sheet, a resist roller that conveys the sheet to said image forming section in predetermined timing, a sheet reading section having a plurality of read pixels for reading an image of the sheet, the method comprising the steps of:

• disposing the sheet reading section in an area which the sheet passes, between said image forming section and said resist roller in such a fashion that the plurality of read pixels are arranged in a direction perpendicular to a direction in which the sheet is fed;
• detecting a leading edge of the sheet by repeatedly reading the plurality of read pixels with a predetermined period;
• and
• determining timing for starting image formation by said image forming section, based on the leading edge of the sheet detected in said leading edge detecting step.

An image formation control method for an image forming apparatus comprising an image forming section that forms an image of an original on a sheet, a resist roller that conveys the sheet to said image forming section in predetermined timing, a sheet reading section having a plurality of read pixels for reading an image of the sheet, the method comprising the steps of:

• disposing the sheet reading section in an area which the sheet passes, between said image forming section and said resist roller in such a fashion that the plurality of read pixels are arranged in a direction perpendicular to a direction in which the sheet is fed;
• detecting a leading edge of the sheet by repeatedly reading the plurality of read pixels with a predetermined period;
• determining timing for starting image formation by said image forming section, based on the leading edge of the sheet detected in said leading edge detecting step;
• detecting a side edge of the sheet by repeatedly reading the plurality of the read pixels read in said leading edge detecting step;
• and
• adjusting a start position of writing the image of the original in the direction perpendicular to the direction in which the sheet is fed, based on the detected side edge of the sheet.