Patent ID: 6760131
Filing Date: 2004-07-06
Classification: H04N

Abstract:
An image scanner comprising:first read means for reading image data on the right side of a document, second read means for reading image data on the reverse side of said document; read control means for controlling said first and second read means so that image data on the right and reverse sides of said document can be read simultaneously; end signal processing means for producing image data on the right and reverse sides of said document by subjecting image data read simultaneously by said first and second read means under the control of said read control means to predetermined operations, said signal processing means comprising a white level control circuit that calculates white level based on image data read by said first and second read means, and a data signal generating circuit that generates image data from image data read by said first and second read means using white level calculated by said white level control circuit; said white level control circuit having a sequence circuit that controls the execution of mutually different white level control depending on the stage of reading image data, an image discriminating circuit that produces an image discriminating instruction by discriminating the state of an image data read by said first and second mad means under the control of said sequence circuit, a white level signal generating circuit that generates a new white level signal by subjecting a current white level signal to predetermined operations in accordance with a predetermined operation designation instruction corresponding to an image discriminating instruction formed by said image discriminating circuit, and a white level memory that stores a new white level signal generated by said white level signal generating circuit as the next white level signal.