Patent ID: 8194299

Claim:
An image forming apparatus comprising: a gradation pattern generation section configured to generate gradation pattern data for plural gradation pattern images; an image forming section configured to form an image to be printed on a recording member, form any of the plural gradation pattern images having gradation on the recording member based on the gradation pattern data, and plural patch pattern images on an image carrier based on patch pattern data, the plural patch pattern images having fixed density values and being to be developed with toner; a reading section configured to read the gradation pattern images from the recording member and output density information of the gradation pattern images; a detection section configured to detect densities of the patch pattern images formed on the image carrier by the image forming section; a gradation correction characteristic generation section configured to generate a first gradation correction characteristic based on the density information outputted by the reading section and a previously held target gradation characteristic, store the first gradation correction characteristic in a storage section, generate a gradation characteristic from the densities detected by the detection section each time at respective different times, generate a second gradation correction characteristic from each generated gradation characteristic, and store the second gradation correction characteristics in the storage section; a calculation section configured to calculate a difference gradation correction characteristic indicative of a difference between the before-mentioned second gradation correction characteristic generated at initial image quality adjustment and the after-mentioned second gradation correction characteristic generated at normal image quality adjustment from the storage section; and an image quality maintaining control section configured to multiply the difference gradation correction characteristic calculated by the calculation section by the first gradation correction characteristic stored in the storage section, and perform gradation correction on image data for the image to be printed based on a third gradation correction characteristic obtained by the multiplication.