Patent ID: 8395825

Claim:
An image scanner for generating image data of a scanned object, said image scanner comprising: a lamp tube serving as a light source to emit light onto said scanned object; an image sensor for producing analog signals of the image of said scanned object; an X-axis white plate arranged on a scanning platform; a Y-axis white plate arranged on said scanning platform; an analog front-end unit for converting said analog signals of the image into digital image data; a gain computing module for generating an X-axis calibration gain to compensate for any error resulted from uneven luminance of said lamp tube, wherein said X-axis calibration gain is stored in a shading table, generating a Y-axis calibration gain to compensate for any error resulted from the unstable luminance of said lamp tube, generating an XY-axis calibration gain according to said X-axis calibration gain and said Y-axis calibration gain, wherein said Y-axis calibration gain is multiplied by said X-axis calibration gain to generate said XY-axis calibration gain, and replacing said X-axis calibration gain in said shading table with said XY-axis calibration gain; and a control and digital computation unit for compensating said digital image data with said XY-axis calibration gain in order to reduce processing time.