Automatic judging device about image read width

An automatic image read width judging device capable of automatically judging a read width in accordance with a width of a manuscript in an image reading section of an image reading apparatus such as a scanner, a facsimile or the like, comprising

• a manuscript guide member which is disposed at a manuscript feeding position of a manuscript conveying means for conveying said manuscript to said image reading section for a slide movement in a width direction of said manuscript crossing a conveying direction from said feeding position and contacts a side edge of said manuscript set in said feeding position for guiding the conveyance of said manuscript,
• position detecting means for detecting a position of said manuscript guide member, said position detecting means having a plate and an optical detecting means in a read section for detecting said plate, said plate opposing said optical detecting means, said plate being associated with said manuscript guide member so as to move in a width direction according to the movement of said manuscript guide member, and said position detecting means being located away from said manuscript guide member in said conveying direction, and
• judging means for judging a read width of an image to be read at said image reading section based on said detected position.