METHOD AND APPARATUS FOR SENSING THE PRESENCE OF A LINE OF DATA FROM A DOCUMENT ON A TRANSPARENT SURFACE

Apparatus and a method for sensing the presence of a document on the transparent surface of an optical scanner involve moving a scanner optics carriage to a predetermined position beneath the transparent surface, reading a line of data, and if any of the data is on the "white" side of the gray-scale relative to a threshold, determining that a document is present in the scanner. Optionally, before determining whether a document is present, the apparatus and method may perform an initial threshold comparison to check for the presence of a dark background to ensure that an old document has been removed before the new document is read. The results of the document presence determination are used to generate a signal which is sent through a scanner interface to the host computer for use in automatically initiating a complete scan of a new document.