Abstract: A method and apparatus for detecting where useful image data about a document exists within a stream of successive scans of image data coming from an imaging camera positioned at a scanning line in an imaging system. A reference member having first, second, and third marks thereon is positioned at the scanning line. Several scans of the reference member provide a reference scan which is retained in the system. When a document reaches the scanning line and is imaged by the imaging camera, a change in the pattern of pixels associated with the reference scan is used to signal the leading edge of a document. After the leading edge is detected, the first mark on the reference member is used to detect from the image data whether or not the document has a folded over portion near the leading and bottom edges of the document. The third mark is used to detect from the image data the location of the top of the document.