Method for correcting registration errors by superimposing a black developer on a background of a color

摘要

A color image forming apparatus causes a light emitting unit to emit light to a superimposed pattern in which a black developer (Bk) is superimposed on a color developer (Y, M, C) as a background color, detects diffuse reflected light by a light receiving unit, calculates positional deviation among the colors using the black developer (Bk) as a reference color based on a detection result, and adjusts an image forming condition.