Image reading device and image forming apparatus with white reference optical adjustment portions

An image reading device comprising:

• contact glass configured to receive placement of an original document;
• a casing that accommodates the contact glass;
• a scanning section accommodated in the casing and including a scanning unit including a plurality of light sources in a row in a main scanning direction that has a length greater than a length of the contact glass in the main scanning direction, the scanning section being configured to read an image of a part at a location opposite to the light sources in the main scanning direction, the image including an image of a part of an original document placed on the contact glass;
• a drive section configured to move the scanning unit in a sub-scanning direction perpendicular to the main scanning direction;
• a document pressing plate configured to be capable of opening and closing relative to the contact glass and press the original document placed on the contact glass against the contact glass when closed;
• an opening and closing detecting section configured to detect opening and closing of the document pressing plate;
• a first white reference plate disposed at a location that is outside a document reading region in the sub-scanning direction and that is readable when the scanner unit is positioned at a first position adjacent to a document reading start position, the first white reference plate having a length in the main scanning direction equal to or greater than a length of the row of the light sources in the main scanning direction, the document reading region being a region in the contact glass across which the scanning unit performs reading;
• a second white reference plate disposed at a location that is readable when the scanner unit is positioned at a second position and where reading of the original document placed on the contact glass is not obstructed in the main scanning direction, the second position being a position that is within the document reading region in the sub-scanning direction and where the scanning unit is positioned in detection of a size of the original document placed on the contact glass;
• an optical adjustment section configured to perform optical adjustment on the scanning section using an output value that the scanning section obtains by reading the first white reference plate;
• and
• a control section that is configured to cause the scanning section to read the first white reference plate when the scanning unit is positioned at the first position for optical adjustment by the optical adjustment section, and cause the scanning unit to move from the first position to the second position for detection of a size of the original document in response to the opening and closing detecting section detecting opening and closing of the document pressing plate in the optical adjustment or reading, wherein
• in a state in which the scanning unit is positioned at the first position, the optical adjustment section performs optical adjustment using an image of the first white reference plate that the scanning section reads while in the state, and
• after the scanning unit is moved to the second position, the optical adjustment section performs optical adjustment using an image of the second white reference plate that the scanning section reads in a state in which the scanning unit is positioned at the second position.