Image reading apparatus for correcting images on both sides of a document sheet

An image reading apparatus comprising:

• a transfer path on which a sheet is transferred;
• a first reading unit positioned on a first side of the transfer path that captures an image on a face of the sheet, the first reading unit including a first light source for emitting light to the face of the sheet from the first side of the transfer path and a plurality of sensors for receiving reflected light from the sheet, the plurality of sensors comprising at least one color sensor for capturing color image data and a first monochrome sensor for capturing monochrome image data;
• a second reading unit positioned on a second side of the transfer path that captures an image on a face of the sheet, the second reading unit including a second light source for emitting light to the face of the sheet from the second side of the transfer path and a sensor for receiving a reflected light from the sheet, the sensor consisting of a second monochrome sensor for capturing monochrome image data;
• a mode selection unit for selecting a monochrome mode or a color mode;
• an inversion unit in the transfer path that inverts the sheet;
• and
• a correction unit that corrects captured first image data so as to substantially equalize image density of the captured first image data with that of captured second image data,
• wherein:
• when the monochrome mode is selected, the captured first image data is captured by the first monochrome sensor in the first reading unit and the captured second image data is captured by the second monochrome sensor in the second reading unit on a single transfer of the sheet through the transfer path,
• when the color mode is selected, the captured first image data is captured by the at least one color sensor in the first reading unit on a first transfer of the sheet through the transfer path, the sheet is inverted by the inversion unit and the captured second image data is captured by the at least one color sensor in the first reading unit on a second transfer of the sheet through the transfer path, and
• the second light source has a wider emission wavelength range than the first light source.

An image reading apparatus comprising:

• a feeder that feeds a sheet;
• a transfer path on which the sheet fed by the feeder is transferred;
• a first reading unit positioned on a first side of the transfer path that captures an image on a face of the sheet from the first side of the transfer path to obtain at least one of color image data or first monochrome image data;
• a second reading unit positioned on a second side of the transfer path that captures an image on a face of the sheet from the second side of the transfer path to obtain second monochrome image data;
• a mode selection unit for selecting a monochrome mode or color mode;
• an inversion unit in the transfer path that inverts the sheet;
• and
• a correction unit that (1) corrects the first monochrome image data captured by the first reading unit and the second monochrome image data captured by the second reading unit in the monochrome mode on a single transfer of the sheet through the transfer path, to substantially equalize image density of the first monochrome image data and the second monochrome image data, and (2) corrects first color image data captured by the first reading unit and second color image data captured by the first reading unit in the color mode on two transfers of the sheet through the transfer path with an inversion in between, to substantially equalize image density of the first color image data and the second color image data.

An image reading apparatus comprising:

• a feeder that feeds a sheet;
• a transfer path on which the sheet fed by the feeder is transferred;
• a first reading unit positioned on a first side of the transfer path that captures an image on a face of the sheet from the first side of the transfer path, the first reading unit including at least one color sensor for capturing color image data and a first monochrome sensor for capturing monochrome image data;
• a second reading unit positioned on a second side of the transfer path that captures an image on a face of the sheet from the second side of the transfer path, the second reading unit consisting of a second monochrome sensor for capturing monochrome image data;
• a mode selection unit for selecting a color mode or a monochrome mode;
• an inversion unit in the transfer path that inverts the sheet;
• and
• an acceptor that accepts a selection concerning correcting an image density of captured image data,
• wherein:
• when the monochrome mode is selected, first image data is captured by the first monochrome sensor in the first reading unit and second image data is captured by the second monochrome sensor in the second reading unit on at a single transfer of the sheet through the transfer path,
• when the color mode is selected, first image data is captured by the at least one color sensor in the in the first reading unit on a first transfer of the sheet through the transfer path, the sheet is inverted by the inversion unit and second image data is captured by the at least one color sensor in the first reading unit on a second transfer of the sheet through the transfer path, and
• the acceptor accepts a selection concerning whether (a) to bring image density of the captured second image data close to that of the captured first image data, or (b) to bring the image density of the captured first image data close to that of the captured second image data.