Patent ID: 6424748
Filing Date: 2002-07-23
Classification: H04N

Abstract:
A transforming method for increasing bit number of digital image signals generated by a scanner, the scanner comprising:a scanning module having a plurality of linearly arranged sensors for scanning a document and generating a plurality of corresponding analog image signals; an A/D (analog to digital) converter for converting each of the analog image signals into a digital image signal with a first bit number; and a white calibration area and a black calibration area for calibrating the scanning module; the transforming method comprising; (1) using the scanning module to scan the white and black calibration areas; (2) generating a plurality of white and black analog image signals through scanning of the white and black calibration areas by each sensor of the scanning module, and generating a plurality of corresponding white and black digital image signals by converting the white and black analog image signals generated by each sensor through use of the A/D converter: and (3) converting each digital image signal generated during scanning of the document by each sensor into a digital image signal with a second bit number according to the white and black digital image signals and a predetermined mapping method wherein the second bit number is greater than the first bit number; wherein the number of white digital image signals generated by each sensor is 2m and can be depicted as Wi (i=1Ëœ2m), where m is an integer, and the number of black digital image signals of each sensor is 2n and can be depicted as Bi (i=1Ëœ2n), where n is an integer, and the mapping method comprises the following steps: (1) adding up all the white digital image signals of each sensor and depicting the sum as Ws wherein Ws=&Sum;i=12m&it;â€ƒ&it;Wi,â€ƒ(2) adding up all the black digital image signals of each sensor and depicting the sum as Bs wherein Bs=&Sum;i=12n&it;â€ƒ&it;Bi,â€ƒ(3) converting each digital image signal (X) generated by the sensor when scanning the document into a transformed real number (R) by the following formula: R=2m+n*X-2m*Bs2n*Ws-2m*Bs,â€ƒ&it;andâ€ƒ(4) transforming the real number into a digital image signal with the second bit number.