1. A document-imaging device with automatic focus capability for capturing images of pages of document objects, the device comprising: one or more light pattern sources that project a predetermined light pattern onto a page of a document object being imaged, wherein the pages of the document object are separated by different thicknesses from an end page of the document object and the projected light pattern varies on the page as a function of the separation of the page from the end page; an optical sensor that senses the light pattern projected onto the page being imaged; and an automatic focus mechanism that focuses an image capture device on the page being imaged based on a variation in the sensed light pattern.