Patent attributes
A color image forming apparatus includes a developing unit to which a developing bias with an AC component superposed is applied, wherein the DC voltage of the developing bias is adjusted to set the detected density of a solid image at a specified value, the light amount of radiation for exposing an image area having a width of a few dots adjacent to the white paper is adjusted to set the detected density of an image developed under a peripheral electric field at a specified value, and the gradation density curve is regulated by alternately adjusting the DC voltage, the light amount of radiation for exposing the image area having a width of a few dots adjacent to the white paper, and the amplitude of the AC component until the detected density of a mesh point image having an area ratio from 60 to 80% falls within a specified range.
