Patent ID: 6930810

Claim:
A correction table forming method for forming correction tables used in a color image forming apparatus having a color scanner and a color printer, said correction table forming method comprising: reading out prestored correction data corresponding to plural colors; generating color signals at predetermined screen angles for the respective colors including black by using the correction data corresponding to the plural colors; printing out the color signals on a sheet by use of the color printer of the color image forming apparatus; reading the printed sheet by use of the color scanner of the color image forming apparatus; converting the read image data to color signals; calculating read data from the converted color signals; comparing and calculating the calculated read data and the correction data corresponding to the plural colors to form correction tables of the respective colors including black; reading out prestored correction data corresponding to mono-color black; generating color signals at a screen angle corresponding to the mono-color black by using the correction data corresponding to the mono-color black; printing out the color signals on a sheet by use of the color printer of the color image forming apparatus; reading the printed sheet by use of the color scanner of the color image forming apparatus; converting the read image data to color signals; calculating read data from the converted color signals; comparing and calculating the calculated read data and the correction data corresponding to the mono-color black to form a correction table of the mono-color black; and forming an error correction table from the correction table of black included in the correction tables of the respective colors and the correction table of the mono-color black.