Document information detecting device for a copying machine

摘要

The invention provides an apparatus for detecting an image on a document for use in a copying machine. A scanner scans the document and photoelectrically reads the image to generate a first analog signal representing a size of the document and a second analog signal representing an image density of the image. A central processing unit processes the first and second analog signals to determine the size and the image density of the document. The central processing unit includes an input port for receiving both of the first and second analog signals and a switch for selectively inputting one of the first and second analog signals at a time into the input port.