| 摘要 |
PURPOSE: To execute shading correction following the deterioration of illumination and photoelectric conversion element by leaving a fixed rate of shading correction data in a holding means by reading an original and substituting peak data in a peak holding means for other correction data. CONSTITUTION: A digital image signal 7 is inputted from an A/D conversion circuit 6 to a shading correction circuit 8. White peak hold memory 22 ignores data in a black part outputted from each picture element of a message sensor 1 by reading the original 3 in a sub scanning direction, and writes white data of maximum value, and collects the white peak data of the original 3. A data conversion circuit 34 substitutes the ratio in shading correction memory 11 by pixel data in the memory 22. When the circuit 8 is operated, white paper is read by setting a mode at an initialization mode to input white reference as the shading correction data to correction memory 1. Such data is written on the memory 11 by an initialization signal via a MUX 28. A shading arithmetic circuit 10 applies the shading correction to the data from the memory 11, and outputs a shading correction signal 9. |
