Patent ID: 8112007

Claim:
An image forming apparatus that performs both a print function and a scan function, the print function including forming an image on an image forming sheet with use of one or more image forming units, and the scan function including generating image data by reading an image of an original, the image forming apparatus comprising: a tone patch storage storing a plurality of tone patches, which are different in tone level, in a one-to-one correspondence with tone levels; a correction table storage storing a tone correction table for correcting relationships between the tone levels and densities of the tone patches; a pattern former operable to, using each of the one or more image forming units, (i) form the tone patches stored in the tone patch storage on the image forming sheet so as to be aligned in one of (a) a main scanning direction and (b) a sub scanning direction, and (ii) form markers, on the image forming sheet, indicating positions of the formed tone patches, the markers being aligned in the aligning direction of the tone patches; a pattern reader operable to read, as the original is read using the scan function, the image forming sheet having the tone patches and the aligned markers formed thereon by the pattern former; a coordinate determiner operable to determine, in the direction of the aligned tone patches, coordinates of the tone patches based on the aligned markers read by the pattern reader; a density determiner operable to determine densities of the tone patches read by the pattern reader based on the determined coordinates; and an updating part operable to update the tone correction table stored by the correction table storage based on relationships between the determined densities and the tone levels corresponding to the tone patches which are stored by the tone patch storage.