Image reading apparatus

An image reading apparatus comprising:

• a reading table comprising a transparent plate comprising an exposed area which constitutes a part of an outer surface of the reading table exposed to the exterior, and on which a document with an image thereon is placed;
• a document holding member movable relative to the reading table and between a closed position and an open position, and thus holding the document and covering the transparent plate;
• a scanning device which is disposed on a side of the transparent plate opposite to the side on which the document is supported on the transparent plate, the scanning device being reciprocated in a predetermined direction along the transparent plate;
• an image reading device mounted in the scanning device and including a light source, the image reading device emitting light from the light source toward the document placed on the transparent plate, and receiving the reflected light from the document, to read the image on the document thereby;
• a control unit which controls reading by the image reading device, and a reciprocating movement of the scanning device;
• a reference member which is disposed within the exposed area on the transparent plate, and used as a reference when an amount of the light emitted from the light source of the image reading device is adjusted;
• and
• an external-light detector which determines whether external light is entering the reading table, based on at least one value obtained as a result of reading the reference member by the image reading device,
• wherein the reference member comprises a white area and a black area that are arranged in the direction of the reciprocation of the scanning device, and
• wherein the external-light detector determines that external light is entering the reading table when a difference between the value obtained by reading the white area while the light source is off and the value obtained by reading the black area while the light source is off, is not less than a predetermined threshold.