Image reading apparatus, and method for detecting size of document

An image reading apparatus that reads an image in a first scanning direction and in a second scanning direction perpendicular to the first scanning direction, the image reading apparatus comprising:

• a document table that has a placing surface on which a document is placed;
• a first positioning member that is provided on the document table to extend in the first scanning direction and determines a position in the second scanning direction of an edge of the document placed on the placing surface;
• a second positioning member that is provided on the document table to extend in the second scanning direction and determines a position in the first scanning direction of an edge of the document placed on the placing surface;
• a light receiving unit that is provided to face one surface of the document placed on the placing surface, and receives reflected light of light emitted to the placing surface;
• a first reference area holding member that extends from the first positioning member over the placing surface and holds, on its surface opposing the placing surface, a first reference area extending parallel to the first scanning direction;
• a second reference area holding member that extends from the second positioning member over the placing surface and holds, on its surface opposing the placing surface, a second reference area extending parallel to the second scanning direction, wherein the first reference area and the second reference area have a same pattern;
• a border position detecting unit that detects a border position in the first scanning direction between the first reference area and the document placed on the placing surface, and a border position in the second scanning direction between the second reference area and the document placed on the placing surface, by determining whether or not a quantity of the reflected light received by the light receiving unit changes across a predetermined threshold value that is commonly used for border detections in the first scanning direction and in the second scanning direction;
• and
• a size determining unit that calculates document lengths in the first scanning direction and in the second scanning direction, based on the border positions in the first scanning direction and the second scanning direction detected by the border position detecting unit.

A method for detecting a size of a document to be read by an image reading apparatus that reads an image of a document placed on a placing surface of a document table in a first scanning direction and in a second scanning direction perpendicular to the first scanning direction, the method comprising:

• determining a position in the second scanning direction of an edge of a document placed on the placing surface by a first positioning member that is provided on the document table to extend in the first scanning direction;
• receiving reflected light from the document placed on the placing surface and at least one of first and second reference areas that are provided to extend in the first scanning direction, wherein the document is placed between the placing surface and the first and second reference areas having different patterns from each other;
• detecting a border position in the first scanning direction between the document placed on the placing surface and at least one of the first and second reference areas, based on the received light quantity of the reflected light;
• and
• calculating a document length in the first scanning direction based on the detected border position.