US Patent 7248388 Optical scanner

An optical scanner includes a first reference white board and a second reference white board perpendicular to two sides of a glass window that holds an object to be scanned. When the optical scanner is powered on, the optical module scans the first reference white board and the second reference white board to obtain data of image quality test and brightness variations in Y direction first, and through software compensation and correction, to obtain a normal digital image data thereby to achieve rapid preview and scanning.