Patent attributes
A document original size detecting device has a plurality of sensors each including a light emitting portion and a light receiving portion and respectively disposed as corresponding to different sizes of document originals to be placed on a transparent document platen and a detecting section which determines a document original size based on outputs of the sensors. The light emitting portion of each of the sensors emits light to illuminate at least two positions on a document placing region of the document platen on which a document original to be subjected to size detection is placed, and the detecting section determines the document original size based on whether or not the light receiving portion of each of the sensors detects the document original blocking the light in at least one of the two positions.
