Document size detecting device and method of detecting document size thereof

摘要

A document size detecting device including a flatbed, a sensing region, a matrix optical sensing unit and a logic processing unit is provided. The flatbed has a first flatbed edge and a second flatbed edge. A first edge and a second edge of the document are respectively aligned with the first flatbed edge and the second flatbed edge. Part of the sensing region is covered by part of the document. The sensing region is formed on the flatbed according to a sensing ability of the matrix optical sensing unit. The matrix optical sensing unit fetches an image from the sensing region and then outputs an image signal accordingly. The logic processing unit receives the image signal and determines the size of the document according to the image signal.