Document scanner without pressure actuated mechanical document sensor and document scanning method thereof

摘要

A document scanner includes a roller to drive the document along a forward path, an image sensor arranged adjacent to the roller to scan the image on the document, and a control unit instructing the operations of the roller and the image sensor. The roller has an outer surface extending in an axial direction on which a plurality of interleaved black and white sections are arranged in a predetermined pattern and having a predetermined axial length. There is also provided a document scanning method associated with the structure of the document scanner, including the steps of (a) actuating the image sensor to perform the sensing operation toward the gray level pattern, storing the gray level value obtained from the sensing operation as the REFERENCE value; (b) actuating the image sensor to periodically perform the sensing operation toward the image viewed by the image sensor so as to obtain the CURRENT value; (c) initiating the scanning operation of the image sensor and the rolling movement of the roller when the CURRENT value and the REFERENCE value are substantially different; terminating the scanning operation of the image sensor and the rolling movement of the roller when the CURRENT value and the REFERENCE value are substantially the same.